A Project Report on

ROAD CONSTRUCTION Public Work Department

National Highway - 330

(Sultanpur)

04th June- 03th July 2015

Submitted By Submitted to

Devnath Prem Chandra Verma

BTech 4th Year (CE) Faculty

RKGEC Ghaziabad RKGEC Civil Department

Ghaziabad

Certificate

This is to certify that the report entitled ldquoROAD CONSTRUCTION ( National Highway - 330)rdquo compiled by Mr Devnath under my supervision

Mr Prem Chandra Verma

(Faculty)

RKGEC Civil Department

Ghaziabad

Acknowledgements

I express my sincere gratitude to Mr Prem Chandra Verma Project guide of my project work who took been interested on my project work and guided me all along till the completion of my project work

The success and final outcome of this project required a lot of guidance and assistance from many people of the bridge workshop and I am extremely fortunate to have got all this all along the completion of this project work

I am also greatly inbeated his for his valuable suggestion in the preparation of the paper

Whatever I have done is only due to such guidance and assistance and I would not forget to thank them

Finaly I greatful acknowledge my family member and my friends for their love support and constant encouragement during the study

DevnathBTech 4th Year (CE)

1230900021

PUBLIC WORKS DEPARTMENT AN OVERVIEW

Public Works Department (PWD) under the Ministry of Public Works department is the pioneer in construction arena of Uttar Pradesh Over about four centuries PWD could successfully set the trend and standard in the state`s infrastructure development It plays a pivotal role in the implementation of government construction projects It also undertakes projects for autonomous bodies as deposit works

Public works Department has highly qualified and experienced professionals forming a multi-disciplinary team of civil electricaland mechanical engineers who work alongside architects from the Department of Architecture With its strong base of standards and professionalism developed over the years PWD is the repository of expertise and hence the first choices among discerning clients for any type of construction project in Uttar Pradesh Besides being the construction agency of the Government it performs regulatory function in setting the pace and managing projects for the countrys construction industry under the close supervision of the Ministry of Housingand Public Works

The Public works Department has highly qualified and experienced professionals forming a multi-disciplinary team of civil electrical and mechanical engineers who work alongside architects from the Department of Architecture As a sister organization falling under the administrative control of the Ministry of Public Works department the latter works well with the PWD in providing service to the nation With its strong base of standards and professionalism developed over the years the PWD is the repository of expertise and hence the first choices among discerning clients for any type of construction project in Bangladesh

It is recognized as a leader and pacesetter in the construction industry because of its consistently superior performance

INTRODUCTION

Development of a country depends on the connectivity of various places with adequate road network Roads are the major channel of transportation for carrying goods and passengers They play a significant role in improving the socio-economic standards of a region Roads constitute the most important mode of communication in areas where railways have not developed much and form the basic infra-structure for the development and economic growth of the country The benefits from the investment in road sector are indirect long-term and not immediately visible Roads are important assets for any nation However merely creating these assets is not enough it has to be planned carefully and a pavement which is not designed properly deteriorates fast India is a large country having huge resource of materials If these local materials are used properly the cost of construction can be reduced There are various type of pavements which differ in their suitability in different environments Each type of pavement has its own merits and demerits Despite a large number of seminars and conference still in India 98 roads are having flexible pavements A lot of research has been made on use of Waste materials but the role of these materials is still limited So there is need to take a holistic approach and mark the areas where these are most suitable India has one of the largest road networks in the world (over 3 million km at present)For the purpose of management and administration roads in India are divided into the following five categories

National Highways (NH)State Highways (SH)Major District Roads (MDR)Other District Roads (ODR)Village Roads (VR)

The National Highways are intended to facilitate medium and long distance inter-city passenger and freight traffic across the country The State Highways are supposed to carry the traffic along major centres within the State Other District Roads and Village Roads provide villages accessibility to meet their social needs as also the means to transport agriculture produce from village to nearby markets Major District Roads provide the secondary function of linkage between main roads and rural roadsPoint of view geographic and population of the state is the nations largest state State Industrial economic and social development of the state and the population of each village is absolutely necessary to re-connect to the main

roads In addition to state important national roads state roads and district roads and their proper broad be made to improve the quality of traffic point of view is of particular importance

Public Works Department to build roads and improve connectivity in rural zones Other District Road and State broad and improvement of rural roads and main routes narrow construction of zones and depleted bridges and brides reconstruction of the bases are transacted on a priority basis Also under Pradhanmantri Gram Sadak Yojana and pre-fabricated construction of rural roads linking the work of other district roads broad Kilometres the scale bases are edited Successful operation of various schemes for the Public Works Department engineers and supervisory boards in different districts of the engineer‟s office has been settled Activities by planning execution and quality control etc remove impediments find joy in relation to the supervision over the activities are focused Various schemes operated by the Department of the Office of the Regional Chief Engineers and Chief Engineers office

Fig (1) National Highway (NH)

Fig (2) Major District Road (MDR)

Fig (3) Village Road (VR)

WHAT IS ROAD OR PAVEMENT

Pavement or Road is an open generally public way for the passage of vehicles people and animals

Pavement is finished with a hard smooth surface It helped make them durable and able to withstand traffic and the environment They have a life span of between 20 ndash 30 years

Road pavements deteriorate over time due to-

The impact of traffic particularly heavy vehicles

Environmental factors such as weather pollution

PURPOSEMany people rely on paved roads to move themselves and their products rapidly and reliably

FUNCTIONS One of the primary functions is load distribution It can be characterized by the tire loads tire configurations repetition of loads and distribution of traffic across the pavement and vehicle speed

Pavement material and geometric design can affect quick and efficient drainage These eliminating moisture problems such as mud and pounding (puddles) Drainage system consists of

Surface drainage Removing all water present on the pavement surface sloping chambers and kerbs

Subsurface drainage Removing water that seep into or is contained in the underlying subgrade

TYPES OF PAVEMENTS

There are various types of pavements depending upon the materials used a briefs description of all types is given here-

FLEXIBLE PAVEMENTS-

Bitumen has been widely used in the construction of flexible pavements for a long time This is the most convenient and simple type of construction The cost of construction of single lane bituminous pavement varies from 20 to 30 lakhs per km in plain areas In some applications however the performance of conventional bitumen may not be considered satisfactory because of the following reasons-

In summer season due to high temperature bitumen becomes soft resulting in bleeding rutting and segregation finally leading to failure of pavement

In winter season due to low temperature the bitumen becomes brittle resulting in cracking ravelling and unevenness which makes the pavement unsuitable for use

In rainy season water enters the pavement resulting into pot holes and sometimes total removal of bituminous layer

In hilly areas due to sub-zero temperature the freeze thaw and heave cycle takes place Due to freezing and melting of ice in bituminous voids volume expansion and contraction occur This leads to pavements failure

The cost of bitumen has been rising continuously In near future there will be scarcity of bitumen and it will be impossible to procure bitumen at very high costs

RIGID PAVEMENTS-

Rigid pavements though costly in initial investment are cheap in long run because of low maintenance costs There are various merits in the use of Rigid pavements (Concrete pavements) are summarized below-

Bitumen is derived from petroleum crude which is in short supply globally and the price of which has been rising steeply India imports nearly 70 of the petroleum crude The demand for bitumen in the coming years is likely to grow steeply far outstripping the availability Hence it will be in Indias interest to

explore alternative binders Cement is available in sufficient quantity in India and its availability in the future is also assured Thus cement concrete roads should be the obvious choice in future road programmes

Besides the easy available of cement concrete roads have a long life and are practically maintenance-free

Another major advantage of concrete roads is the savings in fuel by commercial vehicles to an extent of 14-20 The fuel savings themselves can support a large programme of concreting

Cement concrete roads save a substantial quantity of stone aggregates and this factor must be considered when a choice pavements is made Concrete roads can withstand extreme weather conditions ndash wide rangingtemperatures heavy rainfall and water logging

Though cement concrete roads may cost slightly more than a flexible pavement initially they are economical when whole-life-costing is considered

Reduction in the cost of concrete pavements can be brought about by developing semiself- compacting concrete techniques and the use of closely spaced thin joints RampD efforts should be initiated in this area

TYPES OF CONCRETE PAVEMENTS

1 PLAIN CONCRETE OR SHORT PAVEMENT SLABS

This type of pavement consists of successive slabs whose length is limited to about 25 times the slab thickness At present it is recommended that the paving slabs not be made longer than 5 even if the joints have dowels to transfer the loads The movements as a result of fluctuations in temperature and humidity are concentrated in the joints Normally these joints are sealed to prevent water from penetrating the road structure The width of the pavement slabs is limited to a maximum of 45 m

2 REINFORCED CONCRETE Continuously reinforced concrete-Continuously reinforced concrete pavements are characterised by the absence of transverse joints and are equipped with longitudinal steel reinforcement The diameter of the reinforcing bars is calculated in such a way that cracking can be controlled and that the cracks are uniformly distributed (spacing at 1 to 3 m) The crack width has to remain very small ie less than 03 mmReinforced pavement slabsReinforced concrete pavement slabs are almost never used except for inside or outside industrial floors that are subjected to large loads or if the number of contraction joints has to be limitedSteel fibre concreteThe use of steel fibre concrete pavements is mainly limited to industrial floors However in that sector they are used intensively For road pavements steel fibre concrete can be used for thin or very thin paving slabs or for very specific application

Site Clearance

General Site clearing generally consists of the cutting andor taking down removal and disposal of everything above ground level including objects overhanging the area to be cleared such as tree branches except such trees vegetation structures or parts of structures and other things which are designated in the contract to remain or be removed by others to which the engineer directed to be left undisturbed The material to be cleared usually but not necessarily is limited to trees stumps logs brush undergrowth long grasses crops loose vegetable matter and structureThe entire road area shall be cleared as described above unless otherwise shown on the drawing andor directed by the engineer

Setting out The right of way (ROW) shall be surveyed and set out before any site clearance is cleared out Wooden pegs usually indicate the surveyed rights of ways Procedure for setting out 1 Fixing of centre line of alignment by using total station theodelite 2 Calculating curvature and refractures (for curves and embankment) by using

auto levels or dumpy level 3 To establish traverse bench mark (TBM) at required intervals adjacent to

alignments 4 Location of levels at major conflict junctions 5 To mark the longitudinal and cross sectional pavement structure 6 To make efficient minimum and desired sight distance at major conflicts

and terrain and also setting out of horizontal curves throughout the alignment was done by using theodolite and total survey station Steps involved in surveying

10487661048766 Benchmark 10487661048766 Temporary benchmark at regular intervals 10487661048766 Centre line marking 10487661048766 Road markings

10487661048766 Profile marking (for longitudinal and cross sectional structures) 10487661048766 Establishment of different levels providing gradients as per to design considering different factors like-

Surveying using dumpy level

Plants and equipments Site clearing of trees vegetation undergrowth bushes and minor structures are carried out by dozers and or hydraulic excavators Trees that cannot be felled by the aforesaid equipment shall be felled by using saws Major structures that cannot practically be cleared by hydraulic excavators andor dozers these demolitions can be carried out using pneumatic tools explosives andor otherspecialized equipment depending on the size and type of structures Before commencing explosive demolition all necessary permits and licenses will be obtained and a blasting plan detailing the size of charges locations of holes system of detonation and safety precaution will be forwarded to the engineer together with the request sheets

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Certificate

This is to certify that the report entitled ldquoROAD CONSTRUCTION ( National Highway - 330)rdquo compiled by Mr Devnath under my supervision

Mr Prem Chandra Verma

(Faculty)

RKGEC Civil Department

Ghaziabad

Acknowledgements

I express my sincere gratitude to Mr Prem Chandra Verma Project guide of my project work who took been interested on my project work and guided me all along till the completion of my project work

The success and final outcome of this project required a lot of guidance and assistance from many people of the bridge workshop and I am extremely fortunate to have got all this all along the completion of this project work

I am also greatly inbeated his for his valuable suggestion in the preparation of the paper

Whatever I have done is only due to such guidance and assistance and I would not forget to thank them

Finaly I greatful acknowledge my family member and my friends for their love support and constant encouragement during the study

DevnathBTech 4th Year (CE)

1230900021

PUBLIC WORKS DEPARTMENT AN OVERVIEW

Public Works Department (PWD) under the Ministry of Public Works department is the pioneer in construction arena of Uttar Pradesh Over about four centuries PWD could successfully set the trend and standard in the state`s infrastructure development It plays a pivotal role in the implementation of government construction projects It also undertakes projects for autonomous bodies as deposit works

Public works Department has highly qualified and experienced professionals forming a multi-disciplinary team of civil electricaland mechanical engineers who work alongside architects from the Department of Architecture With its strong base of standards and professionalism developed over the years PWD is the repository of expertise and hence the first choices among discerning clients for any type of construction project in Uttar Pradesh Besides being the construction agency of the Government it performs regulatory function in setting the pace and managing projects for the countrys construction industry under the close supervision of the Ministry of Housingand Public Works

The Public works Department has highly qualified and experienced professionals forming a multi-disciplinary team of civil electrical and mechanical engineers who work alongside architects from the Department of Architecture As a sister organization falling under the administrative control of the Ministry of Public Works department the latter works well with the PWD in providing service to the nation With its strong base of standards and professionalism developed over the years the PWD is the repository of expertise and hence the first choices among discerning clients for any type of construction project in Bangladesh

It is recognized as a leader and pacesetter in the construction industry because of its consistently superior performance

INTRODUCTION

Development of a country depends on the connectivity of various places with adequate road network Roads are the major channel of transportation for carrying goods and passengers They play a significant role in improving the socio-economic standards of a region Roads constitute the most important mode of communication in areas where railways have not developed much and form the basic infra-structure for the development and economic growth of the country The benefits from the investment in road sector are indirect long-term and not immediately visible Roads are important assets for any nation However merely creating these assets is not enough it has to be planned carefully and a pavement which is not designed properly deteriorates fast India is a large country having huge resource of materials If these local materials are used properly the cost of construction can be reduced There are various type of pavements which differ in their suitability in different environments Each type of pavement has its own merits and demerits Despite a large number of seminars and conference still in India 98 roads are having flexible pavements A lot of research has been made on use of Waste materials but the role of these materials is still limited So there is need to take a holistic approach and mark the areas where these are most suitable India has one of the largest road networks in the world (over 3 million km at present)For the purpose of management and administration roads in India are divided into the following five categories

National Highways (NH)State Highways (SH)Major District Roads (MDR)Other District Roads (ODR)Village Roads (VR)

The National Highways are intended to facilitate medium and long distance inter-city passenger and freight traffic across the country The State Highways are supposed to carry the traffic along major centres within the State Other District Roads and Village Roads provide villages accessibility to meet their social needs as also the means to transport agriculture produce from village to nearby markets Major District Roads provide the secondary function of linkage between main roads and rural roadsPoint of view geographic and population of the state is the nations largest state State Industrial economic and social development of the state and the population of each village is absolutely necessary to re-connect to the main

roads In addition to state important national roads state roads and district roads and their proper broad be made to improve the quality of traffic point of view is of particular importance

Public Works Department to build roads and improve connectivity in rural zones Other District Road and State broad and improvement of rural roads and main routes narrow construction of zones and depleted bridges and brides reconstruction of the bases are transacted on a priority basis Also under Pradhanmantri Gram Sadak Yojana and pre-fabricated construction of rural roads linking the work of other district roads broad Kilometres the scale bases are edited Successful operation of various schemes for the Public Works Department engineers and supervisory boards in different districts of the engineer‟s office has been settled Activities by planning execution and quality control etc remove impediments find joy in relation to the supervision over the activities are focused Various schemes operated by the Department of the Office of the Regional Chief Engineers and Chief Engineers office

Fig (1) National Highway (NH)

Fig (2) Major District Road (MDR)

Fig (3) Village Road (VR)

WHAT IS ROAD OR PAVEMENT

Pavement or Road is an open generally public way for the passage of vehicles people and animals

Pavement is finished with a hard smooth surface It helped make them durable and able to withstand traffic and the environment They have a life span of between 20 ndash 30 years

Road pavements deteriorate over time due to-

The impact of traffic particularly heavy vehicles

Environmental factors such as weather pollution

PURPOSEMany people rely on paved roads to move themselves and their products rapidly and reliably

FUNCTIONS One of the primary functions is load distribution It can be characterized by the tire loads tire configurations repetition of loads and distribution of traffic across the pavement and vehicle speed

Pavement material and geometric design can affect quick and efficient drainage These eliminating moisture problems such as mud and pounding (puddles) Drainage system consists of

Surface drainage Removing all water present on the pavement surface sloping chambers and kerbs

Subsurface drainage Removing water that seep into or is contained in the underlying subgrade

TYPES OF PAVEMENTS

There are various types of pavements depending upon the materials used a briefs description of all types is given here-

FLEXIBLE PAVEMENTS-

Bitumen has been widely used in the construction of flexible pavements for a long time This is the most convenient and simple type of construction The cost of construction of single lane bituminous pavement varies from 20 to 30 lakhs per km in plain areas In some applications however the performance of conventional bitumen may not be considered satisfactory because of the following reasons-

In summer season due to high temperature bitumen becomes soft resulting in bleeding rutting and segregation finally leading to failure of pavement

In winter season due to low temperature the bitumen becomes brittle resulting in cracking ravelling and unevenness which makes the pavement unsuitable for use

In rainy season water enters the pavement resulting into pot holes and sometimes total removal of bituminous layer

In hilly areas due to sub-zero temperature the freeze thaw and heave cycle takes place Due to freezing and melting of ice in bituminous voids volume expansion and contraction occur This leads to pavements failure

The cost of bitumen has been rising continuously In near future there will be scarcity of bitumen and it will be impossible to procure bitumen at very high costs

RIGID PAVEMENTS-

Rigid pavements though costly in initial investment are cheap in long run because of low maintenance costs There are various merits in the use of Rigid pavements (Concrete pavements) are summarized below-

Bitumen is derived from petroleum crude which is in short supply globally and the price of which has been rising steeply India imports nearly 70 of the petroleum crude The demand for bitumen in the coming years is likely to grow steeply far outstripping the availability Hence it will be in Indias interest to

explore alternative binders Cement is available in sufficient quantity in India and its availability in the future is also assured Thus cement concrete roads should be the obvious choice in future road programmes

Besides the easy available of cement concrete roads have a long life and are practically maintenance-free

Another major advantage of concrete roads is the savings in fuel by commercial vehicles to an extent of 14-20 The fuel savings themselves can support a large programme of concreting

Cement concrete roads save a substantial quantity of stone aggregates and this factor must be considered when a choice pavements is made Concrete roads can withstand extreme weather conditions ndash wide rangingtemperatures heavy rainfall and water logging

Though cement concrete roads may cost slightly more than a flexible pavement initially they are economical when whole-life-costing is considered

Reduction in the cost of concrete pavements can be brought about by developing semiself- compacting concrete techniques and the use of closely spaced thin joints RampD efforts should be initiated in this area

TYPES OF CONCRETE PAVEMENTS

1 PLAIN CONCRETE OR SHORT PAVEMENT SLABS

This type of pavement consists of successive slabs whose length is limited to about 25 times the slab thickness At present it is recommended that the paving slabs not be made longer than 5 even if the joints have dowels to transfer the loads The movements as a result of fluctuations in temperature and humidity are concentrated in the joints Normally these joints are sealed to prevent water from penetrating the road structure The width of the pavement slabs is limited to a maximum of 45 m

2 REINFORCED CONCRETE Continuously reinforced concrete-Continuously reinforced concrete pavements are characterised by the absence of transverse joints and are equipped with longitudinal steel reinforcement The diameter of the reinforcing bars is calculated in such a way that cracking can be controlled and that the cracks are uniformly distributed (spacing at 1 to 3 m) The crack width has to remain very small ie less than 03 mmReinforced pavement slabsReinforced concrete pavement slabs are almost never used except for inside or outside industrial floors that are subjected to large loads or if the number of contraction joints has to be limitedSteel fibre concreteThe use of steel fibre concrete pavements is mainly limited to industrial floors However in that sector they are used intensively For road pavements steel fibre concrete can be used for thin or very thin paving slabs or for very specific application

Site Clearance

General Site clearing generally consists of the cutting andor taking down removal and disposal of everything above ground level including objects overhanging the area to be cleared such as tree branches except such trees vegetation structures or parts of structures and other things which are designated in the contract to remain or be removed by others to which the engineer directed to be left undisturbed The material to be cleared usually but not necessarily is limited to trees stumps logs brush undergrowth long grasses crops loose vegetable matter and structureThe entire road area shall be cleared as described above unless otherwise shown on the drawing andor directed by the engineer

Setting out The right of way (ROW) shall be surveyed and set out before any site clearance is cleared out Wooden pegs usually indicate the surveyed rights of ways Procedure for setting out 1 Fixing of centre line of alignment by using total station theodelite 2 Calculating curvature and refractures (for curves and embankment) by using

auto levels or dumpy level 3 To establish traverse bench mark (TBM) at required intervals adjacent to

alignments 4 Location of levels at major conflict junctions 5 To mark the longitudinal and cross sectional pavement structure 6 To make efficient minimum and desired sight distance at major conflicts

and terrain and also setting out of horizontal curves throughout the alignment was done by using theodolite and total survey station Steps involved in surveying

10487661048766 Benchmark 10487661048766 Temporary benchmark at regular intervals 10487661048766 Centre line marking 10487661048766 Road markings

10487661048766 Profile marking (for longitudinal and cross sectional structures) 10487661048766 Establishment of different levels providing gradients as per to design considering different factors like-

Surveying using dumpy level

Plants and equipments Site clearing of trees vegetation undergrowth bushes and minor structures are carried out by dozers and or hydraulic excavators Trees that cannot be felled by the aforesaid equipment shall be felled by using saws Major structures that cannot practically be cleared by hydraulic excavators andor dozers these demolitions can be carried out using pneumatic tools explosives andor otherspecialized equipment depending on the size and type of structures Before commencing explosive demolition all necessary permits and licenses will be obtained and a blasting plan detailing the size of charges locations of holes system of detonation and safety precaution will be forwarded to the engineer together with the request sheets

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Acknowledgements

I express my sincere gratitude to Mr Prem Chandra Verma Project guide of my project work who took been interested on my project work and guided me all along till the completion of my project work

The success and final outcome of this project required a lot of guidance and assistance from many people of the bridge workshop and I am extremely fortunate to have got all this all along the completion of this project work

I am also greatly inbeated his for his valuable suggestion in the preparation of the paper

Whatever I have done is only due to such guidance and assistance and I would not forget to thank them

Finaly I greatful acknowledge my family member and my friends for their love support and constant encouragement during the study

DevnathBTech 4th Year (CE)

1230900021

PUBLIC WORKS DEPARTMENT AN OVERVIEW

Public Works Department (PWD) under the Ministry of Public Works department is the pioneer in construction arena of Uttar Pradesh Over about four centuries PWD could successfully set the trend and standard in the state`s infrastructure development It plays a pivotal role in the implementation of government construction projects It also undertakes projects for autonomous bodies as deposit works

Public works Department has highly qualified and experienced professionals forming a multi-disciplinary team of civil electricaland mechanical engineers who work alongside architects from the Department of Architecture With its strong base of standards and professionalism developed over the years PWD is the repository of expertise and hence the first choices among discerning clients for any type of construction project in Uttar Pradesh Besides being the construction agency of the Government it performs regulatory function in setting the pace and managing projects for the countrys construction industry under the close supervision of the Ministry of Housingand Public Works

The Public works Department has highly qualified and experienced professionals forming a multi-disciplinary team of civil electrical and mechanical engineers who work alongside architects from the Department of Architecture As a sister organization falling under the administrative control of the Ministry of Public Works department the latter works well with the PWD in providing service to the nation With its strong base of standards and professionalism developed over the years the PWD is the repository of expertise and hence the first choices among discerning clients for any type of construction project in Bangladesh

It is recognized as a leader and pacesetter in the construction industry because of its consistently superior performance

INTRODUCTION

Development of a country depends on the connectivity of various places with adequate road network Roads are the major channel of transportation for carrying goods and passengers They play a significant role in improving the socio-economic standards of a region Roads constitute the most important mode of communication in areas where railways have not developed much and form the basic infra-structure for the development and economic growth of the country The benefits from the investment in road sector are indirect long-term and not immediately visible Roads are important assets for any nation However merely creating these assets is not enough it has to be planned carefully and a pavement which is not designed properly deteriorates fast India is a large country having huge resource of materials If these local materials are used properly the cost of construction can be reduced There are various type of pavements which differ in their suitability in different environments Each type of pavement has its own merits and demerits Despite a large number of seminars and conference still in India 98 roads are having flexible pavements A lot of research has been made on use of Waste materials but the role of these materials is still limited So there is need to take a holistic approach and mark the areas where these are most suitable India has one of the largest road networks in the world (over 3 million km at present)For the purpose of management and administration roads in India are divided into the following five categories

National Highways (NH)State Highways (SH)Major District Roads (MDR)Other District Roads (ODR)Village Roads (VR)

The National Highways are intended to facilitate medium and long distance inter-city passenger and freight traffic across the country The State Highways are supposed to carry the traffic along major centres within the State Other District Roads and Village Roads provide villages accessibility to meet their social needs as also the means to transport agriculture produce from village to nearby markets Major District Roads provide the secondary function of linkage between main roads and rural roadsPoint of view geographic and population of the state is the nations largest state State Industrial economic and social development of the state and the population of each village is absolutely necessary to re-connect to the main

roads In addition to state important national roads state roads and district roads and their proper broad be made to improve the quality of traffic point of view is of particular importance

Public Works Department to build roads and improve connectivity in rural zones Other District Road and State broad and improvement of rural roads and main routes narrow construction of zones and depleted bridges and brides reconstruction of the bases are transacted on a priority basis Also under Pradhanmantri Gram Sadak Yojana and pre-fabricated construction of rural roads linking the work of other district roads broad Kilometres the scale bases are edited Successful operation of various schemes for the Public Works Department engineers and supervisory boards in different districts of the engineer‟s office has been settled Activities by planning execution and quality control etc remove impediments find joy in relation to the supervision over the activities are focused Various schemes operated by the Department of the Office of the Regional Chief Engineers and Chief Engineers office

Fig (1) National Highway (NH)

Fig (2) Major District Road (MDR)

Fig (3) Village Road (VR)

WHAT IS ROAD OR PAVEMENT

Pavement or Road is an open generally public way for the passage of vehicles people and animals

Pavement is finished with a hard smooth surface It helped make them durable and able to withstand traffic and the environment They have a life span of between 20 ndash 30 years

Road pavements deteriorate over time due to-

The impact of traffic particularly heavy vehicles

Environmental factors such as weather pollution

PURPOSEMany people rely on paved roads to move themselves and their products rapidly and reliably

FUNCTIONS One of the primary functions is load distribution It can be characterized by the tire loads tire configurations repetition of loads and distribution of traffic across the pavement and vehicle speed

Pavement material and geometric design can affect quick and efficient drainage These eliminating moisture problems such as mud and pounding (puddles) Drainage system consists of

Surface drainage Removing all water present on the pavement surface sloping chambers and kerbs

Subsurface drainage Removing water that seep into or is contained in the underlying subgrade

TYPES OF PAVEMENTS

There are various types of pavements depending upon the materials used a briefs description of all types is given here-

FLEXIBLE PAVEMENTS-

Bitumen has been widely used in the construction of flexible pavements for a long time This is the most convenient and simple type of construction The cost of construction of single lane bituminous pavement varies from 20 to 30 lakhs per km in plain areas In some applications however the performance of conventional bitumen may not be considered satisfactory because of the following reasons-

In summer season due to high temperature bitumen becomes soft resulting in bleeding rutting and segregation finally leading to failure of pavement

In winter season due to low temperature the bitumen becomes brittle resulting in cracking ravelling and unevenness which makes the pavement unsuitable for use

In rainy season water enters the pavement resulting into pot holes and sometimes total removal of bituminous layer

In hilly areas due to sub-zero temperature the freeze thaw and heave cycle takes place Due to freezing and melting of ice in bituminous voids volume expansion and contraction occur This leads to pavements failure

The cost of bitumen has been rising continuously In near future there will be scarcity of bitumen and it will be impossible to procure bitumen at very high costs

RIGID PAVEMENTS-

Rigid pavements though costly in initial investment are cheap in long run because of low maintenance costs There are various merits in the use of Rigid pavements (Concrete pavements) are summarized below-

Bitumen is derived from petroleum crude which is in short supply globally and the price of which has been rising steeply India imports nearly 70 of the petroleum crude The demand for bitumen in the coming years is likely to grow steeply far outstripping the availability Hence it will be in Indias interest to

explore alternative binders Cement is available in sufficient quantity in India and its availability in the future is also assured Thus cement concrete roads should be the obvious choice in future road programmes

Besides the easy available of cement concrete roads have a long life and are practically maintenance-free

Another major advantage of concrete roads is the savings in fuel by commercial vehicles to an extent of 14-20 The fuel savings themselves can support a large programme of concreting

Cement concrete roads save a substantial quantity of stone aggregates and this factor must be considered when a choice pavements is made Concrete roads can withstand extreme weather conditions ndash wide rangingtemperatures heavy rainfall and water logging

Though cement concrete roads may cost slightly more than a flexible pavement initially they are economical when whole-life-costing is considered

Reduction in the cost of concrete pavements can be brought about by developing semiself- compacting concrete techniques and the use of closely spaced thin joints RampD efforts should be initiated in this area

TYPES OF CONCRETE PAVEMENTS

1 PLAIN CONCRETE OR SHORT PAVEMENT SLABS

This type of pavement consists of successive slabs whose length is limited to about 25 times the slab thickness At present it is recommended that the paving slabs not be made longer than 5 even if the joints have dowels to transfer the loads The movements as a result of fluctuations in temperature and humidity are concentrated in the joints Normally these joints are sealed to prevent water from penetrating the road structure The width of the pavement slabs is limited to a maximum of 45 m

2 REINFORCED CONCRETE Continuously reinforced concrete-Continuously reinforced concrete pavements are characterised by the absence of transverse joints and are equipped with longitudinal steel reinforcement The diameter of the reinforcing bars is calculated in such a way that cracking can be controlled and that the cracks are uniformly distributed (spacing at 1 to 3 m) The crack width has to remain very small ie less than 03 mmReinforced pavement slabsReinforced concrete pavement slabs are almost never used except for inside or outside industrial floors that are subjected to large loads or if the number of contraction joints has to be limitedSteel fibre concreteThe use of steel fibre concrete pavements is mainly limited to industrial floors However in that sector they are used intensively For road pavements steel fibre concrete can be used for thin or very thin paving slabs or for very specific application

Site Clearance

General Site clearing generally consists of the cutting andor taking down removal and disposal of everything above ground level including objects overhanging the area to be cleared such as tree branches except such trees vegetation structures or parts of structures and other things which are designated in the contract to remain or be removed by others to which the engineer directed to be left undisturbed The material to be cleared usually but not necessarily is limited to trees stumps logs brush undergrowth long grasses crops loose vegetable matter and structureThe entire road area shall be cleared as described above unless otherwise shown on the drawing andor directed by the engineer

Setting out The right of way (ROW) shall be surveyed and set out before any site clearance is cleared out Wooden pegs usually indicate the surveyed rights of ways Procedure for setting out 1 Fixing of centre line of alignment by using total station theodelite 2 Calculating curvature and refractures (for curves and embankment) by using

auto levels or dumpy level 3 To establish traverse bench mark (TBM) at required intervals adjacent to

alignments 4 Location of levels at major conflict junctions 5 To mark the longitudinal and cross sectional pavement structure 6 To make efficient minimum and desired sight distance at major conflicts

and terrain and also setting out of horizontal curves throughout the alignment was done by using theodolite and total survey station Steps involved in surveying

10487661048766 Benchmark 10487661048766 Temporary benchmark at regular intervals 10487661048766 Centre line marking 10487661048766 Road markings

10487661048766 Profile marking (for longitudinal and cross sectional structures) 10487661048766 Establishment of different levels providing gradients as per to design considering different factors like-

Surveying using dumpy level

Plants and equipments Site clearing of trees vegetation undergrowth bushes and minor structures are carried out by dozers and or hydraulic excavators Trees that cannot be felled by the aforesaid equipment shall be felled by using saws Major structures that cannot practically be cleared by hydraulic excavators andor dozers these demolitions can be carried out using pneumatic tools explosives andor otherspecialized equipment depending on the size and type of structures Before commencing explosive demolition all necessary permits and licenses will be obtained and a blasting plan detailing the size of charges locations of holes system of detonation and safety precaution will be forwarded to the engineer together with the request sheets

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

PUBLIC WORKS DEPARTMENT AN OVERVIEW

Public Works Department (PWD) under the Ministry of Public Works department is the pioneer in construction arena of Uttar Pradesh Over about four centuries PWD could successfully set the trend and standard in the state`s infrastructure development It plays a pivotal role in the implementation of government construction projects It also undertakes projects for autonomous bodies as deposit works

Public works Department has highly qualified and experienced professionals forming a multi-disciplinary team of civil electricaland mechanical engineers who work alongside architects from the Department of Architecture With its strong base of standards and professionalism developed over the years PWD is the repository of expertise and hence the first choices among discerning clients for any type of construction project in Uttar Pradesh Besides being the construction agency of the Government it performs regulatory function in setting the pace and managing projects for the countrys construction industry under the close supervision of the Ministry of Housingand Public Works

The Public works Department has highly qualified and experienced professionals forming a multi-disciplinary team of civil electrical and mechanical engineers who work alongside architects from the Department of Architecture As a sister organization falling under the administrative control of the Ministry of Public Works department the latter works well with the PWD in providing service to the nation With its strong base of standards and professionalism developed over the years the PWD is the repository of expertise and hence the first choices among discerning clients for any type of construction project in Bangladesh

It is recognized as a leader and pacesetter in the construction industry because of its consistently superior performance

INTRODUCTION

Development of a country depends on the connectivity of various places with adequate road network Roads are the major channel of transportation for carrying goods and passengers They play a significant role in improving the socio-economic standards of a region Roads constitute the most important mode of communication in areas where railways have not developed much and form the basic infra-structure for the development and economic growth of the country The benefits from the investment in road sector are indirect long-term and not immediately visible Roads are important assets for any nation However merely creating these assets is not enough it has to be planned carefully and a pavement which is not designed properly deteriorates fast India is a large country having huge resource of materials If these local materials are used properly the cost of construction can be reduced There are various type of pavements which differ in their suitability in different environments Each type of pavement has its own merits and demerits Despite a large number of seminars and conference still in India 98 roads are having flexible pavements A lot of research has been made on use of Waste materials but the role of these materials is still limited So there is need to take a holistic approach and mark the areas where these are most suitable India has one of the largest road networks in the world (over 3 million km at present)For the purpose of management and administration roads in India are divided into the following five categories

National Highways (NH)State Highways (SH)Major District Roads (MDR)Other District Roads (ODR)Village Roads (VR)

The National Highways are intended to facilitate medium and long distance inter-city passenger and freight traffic across the country The State Highways are supposed to carry the traffic along major centres within the State Other District Roads and Village Roads provide villages accessibility to meet their social needs as also the means to transport agriculture produce from village to nearby markets Major District Roads provide the secondary function of linkage between main roads and rural roadsPoint of view geographic and population of the state is the nations largest state State Industrial economic and social development of the state and the population of each village is absolutely necessary to re-connect to the main

roads In addition to state important national roads state roads and district roads and their proper broad be made to improve the quality of traffic point of view is of particular importance

Public Works Department to build roads and improve connectivity in rural zones Other District Road and State broad and improvement of rural roads and main routes narrow construction of zones and depleted bridges and brides reconstruction of the bases are transacted on a priority basis Also under Pradhanmantri Gram Sadak Yojana and pre-fabricated construction of rural roads linking the work of other district roads broad Kilometres the scale bases are edited Successful operation of various schemes for the Public Works Department engineers and supervisory boards in different districts of the engineer‟s office has been settled Activities by planning execution and quality control etc remove impediments find joy in relation to the supervision over the activities are focused Various schemes operated by the Department of the Office of the Regional Chief Engineers and Chief Engineers office

Fig (1) National Highway (NH)

Fig (2) Major District Road (MDR)

Fig (3) Village Road (VR)

WHAT IS ROAD OR PAVEMENT

Pavement or Road is an open generally public way for the passage of vehicles people and animals

Pavement is finished with a hard smooth surface It helped make them durable and able to withstand traffic and the environment They have a life span of between 20 ndash 30 years

Road pavements deteriorate over time due to-

The impact of traffic particularly heavy vehicles

Environmental factors such as weather pollution

PURPOSEMany people rely on paved roads to move themselves and their products rapidly and reliably

FUNCTIONS One of the primary functions is load distribution It can be characterized by the tire loads tire configurations repetition of loads and distribution of traffic across the pavement and vehicle speed

Pavement material and geometric design can affect quick and efficient drainage These eliminating moisture problems such as mud and pounding (puddles) Drainage system consists of

Surface drainage Removing all water present on the pavement surface sloping chambers and kerbs

Subsurface drainage Removing water that seep into or is contained in the underlying subgrade

TYPES OF PAVEMENTS

There are various types of pavements depending upon the materials used a briefs description of all types is given here-

FLEXIBLE PAVEMENTS-

Bitumen has been widely used in the construction of flexible pavements for a long time This is the most convenient and simple type of construction The cost of construction of single lane bituminous pavement varies from 20 to 30 lakhs per km in plain areas In some applications however the performance of conventional bitumen may not be considered satisfactory because of the following reasons-

In summer season due to high temperature bitumen becomes soft resulting in bleeding rutting and segregation finally leading to failure of pavement

In winter season due to low temperature the bitumen becomes brittle resulting in cracking ravelling and unevenness which makes the pavement unsuitable for use

In rainy season water enters the pavement resulting into pot holes and sometimes total removal of bituminous layer

In hilly areas due to sub-zero temperature the freeze thaw and heave cycle takes place Due to freezing and melting of ice in bituminous voids volume expansion and contraction occur This leads to pavements failure

The cost of bitumen has been rising continuously In near future there will be scarcity of bitumen and it will be impossible to procure bitumen at very high costs

RIGID PAVEMENTS-

Rigid pavements though costly in initial investment are cheap in long run because of low maintenance costs There are various merits in the use of Rigid pavements (Concrete pavements) are summarized below-

Bitumen is derived from petroleum crude which is in short supply globally and the price of which has been rising steeply India imports nearly 70 of the petroleum crude The demand for bitumen in the coming years is likely to grow steeply far outstripping the availability Hence it will be in Indias interest to

explore alternative binders Cement is available in sufficient quantity in India and its availability in the future is also assured Thus cement concrete roads should be the obvious choice in future road programmes

Besides the easy available of cement concrete roads have a long life and are practically maintenance-free

Another major advantage of concrete roads is the savings in fuel by commercial vehicles to an extent of 14-20 The fuel savings themselves can support a large programme of concreting

Cement concrete roads save a substantial quantity of stone aggregates and this factor must be considered when a choice pavements is made Concrete roads can withstand extreme weather conditions ndash wide rangingtemperatures heavy rainfall and water logging

Though cement concrete roads may cost slightly more than a flexible pavement initially they are economical when whole-life-costing is considered

Reduction in the cost of concrete pavements can be brought about by developing semiself- compacting concrete techniques and the use of closely spaced thin joints RampD efforts should be initiated in this area

TYPES OF CONCRETE PAVEMENTS

1 PLAIN CONCRETE OR SHORT PAVEMENT SLABS

This type of pavement consists of successive slabs whose length is limited to about 25 times the slab thickness At present it is recommended that the paving slabs not be made longer than 5 even if the joints have dowels to transfer the loads The movements as a result of fluctuations in temperature and humidity are concentrated in the joints Normally these joints are sealed to prevent water from penetrating the road structure The width of the pavement slabs is limited to a maximum of 45 m

2 REINFORCED CONCRETE Continuously reinforced concrete-Continuously reinforced concrete pavements are characterised by the absence of transverse joints and are equipped with longitudinal steel reinforcement The diameter of the reinforcing bars is calculated in such a way that cracking can be controlled and that the cracks are uniformly distributed (spacing at 1 to 3 m) The crack width has to remain very small ie less than 03 mmReinforced pavement slabsReinforced concrete pavement slabs are almost never used except for inside or outside industrial floors that are subjected to large loads or if the number of contraction joints has to be limitedSteel fibre concreteThe use of steel fibre concrete pavements is mainly limited to industrial floors However in that sector they are used intensively For road pavements steel fibre concrete can be used for thin or very thin paving slabs or for very specific application

Site Clearance

General Site clearing generally consists of the cutting andor taking down removal and disposal of everything above ground level including objects overhanging the area to be cleared such as tree branches except such trees vegetation structures or parts of structures and other things which are designated in the contract to remain or be removed by others to which the engineer directed to be left undisturbed The material to be cleared usually but not necessarily is limited to trees stumps logs brush undergrowth long grasses crops loose vegetable matter and structureThe entire road area shall be cleared as described above unless otherwise shown on the drawing andor directed by the engineer

Setting out The right of way (ROW) shall be surveyed and set out before any site clearance is cleared out Wooden pegs usually indicate the surveyed rights of ways Procedure for setting out 1 Fixing of centre line of alignment by using total station theodelite 2 Calculating curvature and refractures (for curves and embankment) by using

auto levels or dumpy level 3 To establish traverse bench mark (TBM) at required intervals adjacent to

alignments 4 Location of levels at major conflict junctions 5 To mark the longitudinal and cross sectional pavement structure 6 To make efficient minimum and desired sight distance at major conflicts

and terrain and also setting out of horizontal curves throughout the alignment was done by using theodolite and total survey station Steps involved in surveying

10487661048766 Benchmark 10487661048766 Temporary benchmark at regular intervals 10487661048766 Centre line marking 10487661048766 Road markings

10487661048766 Profile marking (for longitudinal and cross sectional structures) 10487661048766 Establishment of different levels providing gradients as per to design considering different factors like-

Surveying using dumpy level

Plants and equipments Site clearing of trees vegetation undergrowth bushes and minor structures are carried out by dozers and or hydraulic excavators Trees that cannot be felled by the aforesaid equipment shall be felled by using saws Major structures that cannot practically be cleared by hydraulic excavators andor dozers these demolitions can be carried out using pneumatic tools explosives andor otherspecialized equipment depending on the size and type of structures Before commencing explosive demolition all necessary permits and licenses will be obtained and a blasting plan detailing the size of charges locations of holes system of detonation and safety precaution will be forwarded to the engineer together with the request sheets

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

INTRODUCTION

Development of a country depends on the connectivity of various places with adequate road network Roads are the major channel of transportation for carrying goods and passengers They play a significant role in improving the socio-economic standards of a region Roads constitute the most important mode of communication in areas where railways have not developed much and form the basic infra-structure for the development and economic growth of the country The benefits from the investment in road sector are indirect long-term and not immediately visible Roads are important assets for any nation However merely creating these assets is not enough it has to be planned carefully and a pavement which is not designed properly deteriorates fast India is a large country having huge resource of materials If these local materials are used properly the cost of construction can be reduced There are various type of pavements which differ in their suitability in different environments Each type of pavement has its own merits and demerits Despite a large number of seminars and conference still in India 98 roads are having flexible pavements A lot of research has been made on use of Waste materials but the role of these materials is still limited So there is need to take a holistic approach and mark the areas where these are most suitable India has one of the largest road networks in the world (over 3 million km at present)For the purpose of management and administration roads in India are divided into the following five categories

National Highways (NH)State Highways (SH)Major District Roads (MDR)Other District Roads (ODR)Village Roads (VR)

The National Highways are intended to facilitate medium and long distance inter-city passenger and freight traffic across the country The State Highways are supposed to carry the traffic along major centres within the State Other District Roads and Village Roads provide villages accessibility to meet their social needs as also the means to transport agriculture produce from village to nearby markets Major District Roads provide the secondary function of linkage between main roads and rural roadsPoint of view geographic and population of the state is the nations largest state State Industrial economic and social development of the state and the population of each village is absolutely necessary to re-connect to the main

roads In addition to state important national roads state roads and district roads and their proper broad be made to improve the quality of traffic point of view is of particular importance

Public Works Department to build roads and improve connectivity in rural zones Other District Road and State broad and improvement of rural roads and main routes narrow construction of zones and depleted bridges and brides reconstruction of the bases are transacted on a priority basis Also under Pradhanmantri Gram Sadak Yojana and pre-fabricated construction of rural roads linking the work of other district roads broad Kilometres the scale bases are edited Successful operation of various schemes for the Public Works Department engineers and supervisory boards in different districts of the engineer‟s office has been settled Activities by planning execution and quality control etc remove impediments find joy in relation to the supervision over the activities are focused Various schemes operated by the Department of the Office of the Regional Chief Engineers and Chief Engineers office

Fig (1) National Highway (NH)

Fig (2) Major District Road (MDR)

Fig (3) Village Road (VR)

WHAT IS ROAD OR PAVEMENT

Pavement or Road is an open generally public way for the passage of vehicles people and animals

Pavement is finished with a hard smooth surface It helped make them durable and able to withstand traffic and the environment They have a life span of between 20 ndash 30 years

Road pavements deteriorate over time due to-

The impact of traffic particularly heavy vehicles

Environmental factors such as weather pollution

PURPOSEMany people rely on paved roads to move themselves and their products rapidly and reliably

FUNCTIONS One of the primary functions is load distribution It can be characterized by the tire loads tire configurations repetition of loads and distribution of traffic across the pavement and vehicle speed

Pavement material and geometric design can affect quick and efficient drainage These eliminating moisture problems such as mud and pounding (puddles) Drainage system consists of

Surface drainage Removing all water present on the pavement surface sloping chambers and kerbs

Subsurface drainage Removing water that seep into or is contained in the underlying subgrade

TYPES OF PAVEMENTS

There are various types of pavements depending upon the materials used a briefs description of all types is given here-

FLEXIBLE PAVEMENTS-

Bitumen has been widely used in the construction of flexible pavements for a long time This is the most convenient and simple type of construction The cost of construction of single lane bituminous pavement varies from 20 to 30 lakhs per km in plain areas In some applications however the performance of conventional bitumen may not be considered satisfactory because of the following reasons-

In summer season due to high temperature bitumen becomes soft resulting in bleeding rutting and segregation finally leading to failure of pavement

In winter season due to low temperature the bitumen becomes brittle resulting in cracking ravelling and unevenness which makes the pavement unsuitable for use

In rainy season water enters the pavement resulting into pot holes and sometimes total removal of bituminous layer

In hilly areas due to sub-zero temperature the freeze thaw and heave cycle takes place Due to freezing and melting of ice in bituminous voids volume expansion and contraction occur This leads to pavements failure

The cost of bitumen has been rising continuously In near future there will be scarcity of bitumen and it will be impossible to procure bitumen at very high costs

RIGID PAVEMENTS-

Rigid pavements though costly in initial investment are cheap in long run because of low maintenance costs There are various merits in the use of Rigid pavements (Concrete pavements) are summarized below-

Bitumen is derived from petroleum crude which is in short supply globally and the price of which has been rising steeply India imports nearly 70 of the petroleum crude The demand for bitumen in the coming years is likely to grow steeply far outstripping the availability Hence it will be in Indias interest to

explore alternative binders Cement is available in sufficient quantity in India and its availability in the future is also assured Thus cement concrete roads should be the obvious choice in future road programmes

Besides the easy available of cement concrete roads have a long life and are practically maintenance-free

Another major advantage of concrete roads is the savings in fuel by commercial vehicles to an extent of 14-20 The fuel savings themselves can support a large programme of concreting

Cement concrete roads save a substantial quantity of stone aggregates and this factor must be considered when a choice pavements is made Concrete roads can withstand extreme weather conditions ndash wide rangingtemperatures heavy rainfall and water logging

Though cement concrete roads may cost slightly more than a flexible pavement initially they are economical when whole-life-costing is considered

Reduction in the cost of concrete pavements can be brought about by developing semiself- compacting concrete techniques and the use of closely spaced thin joints RampD efforts should be initiated in this area

TYPES OF CONCRETE PAVEMENTS

1 PLAIN CONCRETE OR SHORT PAVEMENT SLABS

This type of pavement consists of successive slabs whose length is limited to about 25 times the slab thickness At present it is recommended that the paving slabs not be made longer than 5 even if the joints have dowels to transfer the loads The movements as a result of fluctuations in temperature and humidity are concentrated in the joints Normally these joints are sealed to prevent water from penetrating the road structure The width of the pavement slabs is limited to a maximum of 45 m

2 REINFORCED CONCRETE Continuously reinforced concrete-Continuously reinforced concrete pavements are characterised by the absence of transverse joints and are equipped with longitudinal steel reinforcement The diameter of the reinforcing bars is calculated in such a way that cracking can be controlled and that the cracks are uniformly distributed (spacing at 1 to 3 m) The crack width has to remain very small ie less than 03 mmReinforced pavement slabsReinforced concrete pavement slabs are almost never used except for inside or outside industrial floors that are subjected to large loads or if the number of contraction joints has to be limitedSteel fibre concreteThe use of steel fibre concrete pavements is mainly limited to industrial floors However in that sector they are used intensively For road pavements steel fibre concrete can be used for thin or very thin paving slabs or for very specific application

Site Clearance

General Site clearing generally consists of the cutting andor taking down removal and disposal of everything above ground level including objects overhanging the area to be cleared such as tree branches except such trees vegetation structures or parts of structures and other things which are designated in the contract to remain or be removed by others to which the engineer directed to be left undisturbed The material to be cleared usually but not necessarily is limited to trees stumps logs brush undergrowth long grasses crops loose vegetable matter and structureThe entire road area shall be cleared as described above unless otherwise shown on the drawing andor directed by the engineer

Setting out The right of way (ROW) shall be surveyed and set out before any site clearance is cleared out Wooden pegs usually indicate the surveyed rights of ways Procedure for setting out 1 Fixing of centre line of alignment by using total station theodelite 2 Calculating curvature and refractures (for curves and embankment) by using

auto levels or dumpy level 3 To establish traverse bench mark (TBM) at required intervals adjacent to

alignments 4 Location of levels at major conflict junctions 5 To mark the longitudinal and cross sectional pavement structure 6 To make efficient minimum and desired sight distance at major conflicts

and terrain and also setting out of horizontal curves throughout the alignment was done by using theodolite and total survey station Steps involved in surveying

10487661048766 Benchmark 10487661048766 Temporary benchmark at regular intervals 10487661048766 Centre line marking 10487661048766 Road markings

10487661048766 Profile marking (for longitudinal and cross sectional structures) 10487661048766 Establishment of different levels providing gradients as per to design considering different factors like-

Surveying using dumpy level

Plants and equipments Site clearing of trees vegetation undergrowth bushes and minor structures are carried out by dozers and or hydraulic excavators Trees that cannot be felled by the aforesaid equipment shall be felled by using saws Major structures that cannot practically be cleared by hydraulic excavators andor dozers these demolitions can be carried out using pneumatic tools explosives andor otherspecialized equipment depending on the size and type of structures Before commencing explosive demolition all necessary permits and licenses will be obtained and a blasting plan detailing the size of charges locations of holes system of detonation and safety precaution will be forwarded to the engineer together with the request sheets

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

roads In addition to state important national roads state roads and district roads and their proper broad be made to improve the quality of traffic point of view is of particular importance

Public Works Department to build roads and improve connectivity in rural zones Other District Road and State broad and improvement of rural roads and main routes narrow construction of zones and depleted bridges and brides reconstruction of the bases are transacted on a priority basis Also under Pradhanmantri Gram Sadak Yojana and pre-fabricated construction of rural roads linking the work of other district roads broad Kilometres the scale bases are edited Successful operation of various schemes for the Public Works Department engineers and supervisory boards in different districts of the engineer‟s office has been settled Activities by planning execution and quality control etc remove impediments find joy in relation to the supervision over the activities are focused Various schemes operated by the Department of the Office of the Regional Chief Engineers and Chief Engineers office

Fig (1) National Highway (NH)

Fig (2) Major District Road (MDR)

Fig (3) Village Road (VR)

WHAT IS ROAD OR PAVEMENT

Pavement or Road is an open generally public way for the passage of vehicles people and animals

Pavement is finished with a hard smooth surface It helped make them durable and able to withstand traffic and the environment They have a life span of between 20 ndash 30 years

Road pavements deteriorate over time due to-

The impact of traffic particularly heavy vehicles

Environmental factors such as weather pollution

PURPOSEMany people rely on paved roads to move themselves and their products rapidly and reliably

FUNCTIONS One of the primary functions is load distribution It can be characterized by the tire loads tire configurations repetition of loads and distribution of traffic across the pavement and vehicle speed

Pavement material and geometric design can affect quick and efficient drainage These eliminating moisture problems such as mud and pounding (puddles) Drainage system consists of

Surface drainage Removing all water present on the pavement surface sloping chambers and kerbs

Subsurface drainage Removing water that seep into or is contained in the underlying subgrade

TYPES OF PAVEMENTS

There are various types of pavements depending upon the materials used a briefs description of all types is given here-

FLEXIBLE PAVEMENTS-

Bitumen has been widely used in the construction of flexible pavements for a long time This is the most convenient and simple type of construction The cost of construction of single lane bituminous pavement varies from 20 to 30 lakhs per km in plain areas In some applications however the performance of conventional bitumen may not be considered satisfactory because of the following reasons-

In summer season due to high temperature bitumen becomes soft resulting in bleeding rutting and segregation finally leading to failure of pavement

In winter season due to low temperature the bitumen becomes brittle resulting in cracking ravelling and unevenness which makes the pavement unsuitable for use

In rainy season water enters the pavement resulting into pot holes and sometimes total removal of bituminous layer

In hilly areas due to sub-zero temperature the freeze thaw and heave cycle takes place Due to freezing and melting of ice in bituminous voids volume expansion and contraction occur This leads to pavements failure

The cost of bitumen has been rising continuously In near future there will be scarcity of bitumen and it will be impossible to procure bitumen at very high costs

RIGID PAVEMENTS-

Rigid pavements though costly in initial investment are cheap in long run because of low maintenance costs There are various merits in the use of Rigid pavements (Concrete pavements) are summarized below-

Bitumen is derived from petroleum crude which is in short supply globally and the price of which has been rising steeply India imports nearly 70 of the petroleum crude The demand for bitumen in the coming years is likely to grow steeply far outstripping the availability Hence it will be in Indias interest to

explore alternative binders Cement is available in sufficient quantity in India and its availability in the future is also assured Thus cement concrete roads should be the obvious choice in future road programmes

Besides the easy available of cement concrete roads have a long life and are practically maintenance-free

Another major advantage of concrete roads is the savings in fuel by commercial vehicles to an extent of 14-20 The fuel savings themselves can support a large programme of concreting

Cement concrete roads save a substantial quantity of stone aggregates and this factor must be considered when a choice pavements is made Concrete roads can withstand extreme weather conditions ndash wide rangingtemperatures heavy rainfall and water logging

Though cement concrete roads may cost slightly more than a flexible pavement initially they are economical when whole-life-costing is considered

Reduction in the cost of concrete pavements can be brought about by developing semiself- compacting concrete techniques and the use of closely spaced thin joints RampD efforts should be initiated in this area

TYPES OF CONCRETE PAVEMENTS

1 PLAIN CONCRETE OR SHORT PAVEMENT SLABS

This type of pavement consists of successive slabs whose length is limited to about 25 times the slab thickness At present it is recommended that the paving slabs not be made longer than 5 even if the joints have dowels to transfer the loads The movements as a result of fluctuations in temperature and humidity are concentrated in the joints Normally these joints are sealed to prevent water from penetrating the road structure The width of the pavement slabs is limited to a maximum of 45 m

2 REINFORCED CONCRETE Continuously reinforced concrete-Continuously reinforced concrete pavements are characterised by the absence of transverse joints and are equipped with longitudinal steel reinforcement The diameter of the reinforcing bars is calculated in such a way that cracking can be controlled and that the cracks are uniformly distributed (spacing at 1 to 3 m) The crack width has to remain very small ie less than 03 mmReinforced pavement slabsReinforced concrete pavement slabs are almost never used except for inside or outside industrial floors that are subjected to large loads or if the number of contraction joints has to be limitedSteel fibre concreteThe use of steel fibre concrete pavements is mainly limited to industrial floors However in that sector they are used intensively For road pavements steel fibre concrete can be used for thin or very thin paving slabs or for very specific application

Site Clearance

General Site clearing generally consists of the cutting andor taking down removal and disposal of everything above ground level including objects overhanging the area to be cleared such as tree branches except such trees vegetation structures or parts of structures and other things which are designated in the contract to remain or be removed by others to which the engineer directed to be left undisturbed The material to be cleared usually but not necessarily is limited to trees stumps logs brush undergrowth long grasses crops loose vegetable matter and structureThe entire road area shall be cleared as described above unless otherwise shown on the drawing andor directed by the engineer

Setting out The right of way (ROW) shall be surveyed and set out before any site clearance is cleared out Wooden pegs usually indicate the surveyed rights of ways Procedure for setting out 1 Fixing of centre line of alignment by using total station theodelite 2 Calculating curvature and refractures (for curves and embankment) by using

auto levels or dumpy level 3 To establish traverse bench mark (TBM) at required intervals adjacent to

alignments 4 Location of levels at major conflict junctions 5 To mark the longitudinal and cross sectional pavement structure 6 To make efficient minimum and desired sight distance at major conflicts

and terrain and also setting out of horizontal curves throughout the alignment was done by using theodolite and total survey station Steps involved in surveying

10487661048766 Benchmark 10487661048766 Temporary benchmark at regular intervals 10487661048766 Centre line marking 10487661048766 Road markings

10487661048766 Profile marking (for longitudinal and cross sectional structures) 10487661048766 Establishment of different levels providing gradients as per to design considering different factors like-

Surveying using dumpy level

Plants and equipments Site clearing of trees vegetation undergrowth bushes and minor structures are carried out by dozers and or hydraulic excavators Trees that cannot be felled by the aforesaid equipment shall be felled by using saws Major structures that cannot practically be cleared by hydraulic excavators andor dozers these demolitions can be carried out using pneumatic tools explosives andor otherspecialized equipment depending on the size and type of structures Before commencing explosive demolition all necessary permits and licenses will be obtained and a blasting plan detailing the size of charges locations of holes system of detonation and safety precaution will be forwarded to the engineer together with the request sheets

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Fig (1) National Highway (NH)

Fig (2) Major District Road (MDR)

Fig (3) Village Road (VR)

WHAT IS ROAD OR PAVEMENT

Pavement or Road is an open generally public way for the passage of vehicles people and animals

Pavement is finished with a hard smooth surface It helped make them durable and able to withstand traffic and the environment They have a life span of between 20 ndash 30 years

Road pavements deteriorate over time due to-

The impact of traffic particularly heavy vehicles

Environmental factors such as weather pollution

PURPOSEMany people rely on paved roads to move themselves and their products rapidly and reliably

FUNCTIONS One of the primary functions is load distribution It can be characterized by the tire loads tire configurations repetition of loads and distribution of traffic across the pavement and vehicle speed

Pavement material and geometric design can affect quick and efficient drainage These eliminating moisture problems such as mud and pounding (puddles) Drainage system consists of

Surface drainage Removing all water present on the pavement surface sloping chambers and kerbs

Subsurface drainage Removing water that seep into or is contained in the underlying subgrade

TYPES OF PAVEMENTS

There are various types of pavements depending upon the materials used a briefs description of all types is given here-

FLEXIBLE PAVEMENTS-

Bitumen has been widely used in the construction of flexible pavements for a long time This is the most convenient and simple type of construction The cost of construction of single lane bituminous pavement varies from 20 to 30 lakhs per km in plain areas In some applications however the performance of conventional bitumen may not be considered satisfactory because of the following reasons-

In summer season due to high temperature bitumen becomes soft resulting in bleeding rutting and segregation finally leading to failure of pavement

In winter season due to low temperature the bitumen becomes brittle resulting in cracking ravelling and unevenness which makes the pavement unsuitable for use

In rainy season water enters the pavement resulting into pot holes and sometimes total removal of bituminous layer

In hilly areas due to sub-zero temperature the freeze thaw and heave cycle takes place Due to freezing and melting of ice in bituminous voids volume expansion and contraction occur This leads to pavements failure

The cost of bitumen has been rising continuously In near future there will be scarcity of bitumen and it will be impossible to procure bitumen at very high costs

RIGID PAVEMENTS-

Rigid pavements though costly in initial investment are cheap in long run because of low maintenance costs There are various merits in the use of Rigid pavements (Concrete pavements) are summarized below-

Bitumen is derived from petroleum crude which is in short supply globally and the price of which has been rising steeply India imports nearly 70 of the petroleum crude The demand for bitumen in the coming years is likely to grow steeply far outstripping the availability Hence it will be in Indias interest to

explore alternative binders Cement is available in sufficient quantity in India and its availability in the future is also assured Thus cement concrete roads should be the obvious choice in future road programmes

Besides the easy available of cement concrete roads have a long life and are practically maintenance-free

Another major advantage of concrete roads is the savings in fuel by commercial vehicles to an extent of 14-20 The fuel savings themselves can support a large programme of concreting

Cement concrete roads save a substantial quantity of stone aggregates and this factor must be considered when a choice pavements is made Concrete roads can withstand extreme weather conditions ndash wide rangingtemperatures heavy rainfall and water logging

Though cement concrete roads may cost slightly more than a flexible pavement initially they are economical when whole-life-costing is considered

Reduction in the cost of concrete pavements can be brought about by developing semiself- compacting concrete techniques and the use of closely spaced thin joints RampD efforts should be initiated in this area

TYPES OF CONCRETE PAVEMENTS

1 PLAIN CONCRETE OR SHORT PAVEMENT SLABS

This type of pavement consists of successive slabs whose length is limited to about 25 times the slab thickness At present it is recommended that the paving slabs not be made longer than 5 even if the joints have dowels to transfer the loads The movements as a result of fluctuations in temperature and humidity are concentrated in the joints Normally these joints are sealed to prevent water from penetrating the road structure The width of the pavement slabs is limited to a maximum of 45 m

2 REINFORCED CONCRETE Continuously reinforced concrete-Continuously reinforced concrete pavements are characterised by the absence of transverse joints and are equipped with longitudinal steel reinforcement The diameter of the reinforcing bars is calculated in such a way that cracking can be controlled and that the cracks are uniformly distributed (spacing at 1 to 3 m) The crack width has to remain very small ie less than 03 mmReinforced pavement slabsReinforced concrete pavement slabs are almost never used except for inside or outside industrial floors that are subjected to large loads or if the number of contraction joints has to be limitedSteel fibre concreteThe use of steel fibre concrete pavements is mainly limited to industrial floors However in that sector they are used intensively For road pavements steel fibre concrete can be used for thin or very thin paving slabs or for very specific application

Site Clearance

General Site clearing generally consists of the cutting andor taking down removal and disposal of everything above ground level including objects overhanging the area to be cleared such as tree branches except such trees vegetation structures or parts of structures and other things which are designated in the contract to remain or be removed by others to which the engineer directed to be left undisturbed The material to be cleared usually but not necessarily is limited to trees stumps logs brush undergrowth long grasses crops loose vegetable matter and structureThe entire road area shall be cleared as described above unless otherwise shown on the drawing andor directed by the engineer

Setting out The right of way (ROW) shall be surveyed and set out before any site clearance is cleared out Wooden pegs usually indicate the surveyed rights of ways Procedure for setting out 1 Fixing of centre line of alignment by using total station theodelite 2 Calculating curvature and refractures (for curves and embankment) by using

auto levels or dumpy level 3 To establish traverse bench mark (TBM) at required intervals adjacent to

alignments 4 Location of levels at major conflict junctions 5 To mark the longitudinal and cross sectional pavement structure 6 To make efficient minimum and desired sight distance at major conflicts

and terrain and also setting out of horizontal curves throughout the alignment was done by using theodolite and total survey station Steps involved in surveying

10487661048766 Benchmark 10487661048766 Temporary benchmark at regular intervals 10487661048766 Centre line marking 10487661048766 Road markings

10487661048766 Profile marking (for longitudinal and cross sectional structures) 10487661048766 Establishment of different levels providing gradients as per to design considering different factors like-

Surveying using dumpy level

Plants and equipments Site clearing of trees vegetation undergrowth bushes and minor structures are carried out by dozers and or hydraulic excavators Trees that cannot be felled by the aforesaid equipment shall be felled by using saws Major structures that cannot practically be cleared by hydraulic excavators andor dozers these demolitions can be carried out using pneumatic tools explosives andor otherspecialized equipment depending on the size and type of structures Before commencing explosive demolition all necessary permits and licenses will be obtained and a blasting plan detailing the size of charges locations of holes system of detonation and safety precaution will be forwarded to the engineer together with the request sheets

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

WHAT IS ROAD OR PAVEMENT

Pavement or Road is an open generally public way for the passage of vehicles people and animals

Pavement is finished with a hard smooth surface It helped make them durable and able to withstand traffic and the environment They have a life span of between 20 ndash 30 years

Road pavements deteriorate over time due to-

The impact of traffic particularly heavy vehicles

Environmental factors such as weather pollution

PURPOSEMany people rely on paved roads to move themselves and their products rapidly and reliably

FUNCTIONS One of the primary functions is load distribution It can be characterized by the tire loads tire configurations repetition of loads and distribution of traffic across the pavement and vehicle speed

Pavement material and geometric design can affect quick and efficient drainage These eliminating moisture problems such as mud and pounding (puddles) Drainage system consists of

Surface drainage Removing all water present on the pavement surface sloping chambers and kerbs

Subsurface drainage Removing water that seep into or is contained in the underlying subgrade

TYPES OF PAVEMENTS

There are various types of pavements depending upon the materials used a briefs description of all types is given here-

FLEXIBLE PAVEMENTS-

Bitumen has been widely used in the construction of flexible pavements for a long time This is the most convenient and simple type of construction The cost of construction of single lane bituminous pavement varies from 20 to 30 lakhs per km in plain areas In some applications however the performance of conventional bitumen may not be considered satisfactory because of the following reasons-

In summer season due to high temperature bitumen becomes soft resulting in bleeding rutting and segregation finally leading to failure of pavement

In winter season due to low temperature the bitumen becomes brittle resulting in cracking ravelling and unevenness which makes the pavement unsuitable for use

In rainy season water enters the pavement resulting into pot holes and sometimes total removal of bituminous layer

In hilly areas due to sub-zero temperature the freeze thaw and heave cycle takes place Due to freezing and melting of ice in bituminous voids volume expansion and contraction occur This leads to pavements failure

The cost of bitumen has been rising continuously In near future there will be scarcity of bitumen and it will be impossible to procure bitumen at very high costs

RIGID PAVEMENTS-

Rigid pavements though costly in initial investment are cheap in long run because of low maintenance costs There are various merits in the use of Rigid pavements (Concrete pavements) are summarized below-

Bitumen is derived from petroleum crude which is in short supply globally and the price of which has been rising steeply India imports nearly 70 of the petroleum crude The demand for bitumen in the coming years is likely to grow steeply far outstripping the availability Hence it will be in Indias interest to

explore alternative binders Cement is available in sufficient quantity in India and its availability in the future is also assured Thus cement concrete roads should be the obvious choice in future road programmes

Besides the easy available of cement concrete roads have a long life and are practically maintenance-free

Another major advantage of concrete roads is the savings in fuel by commercial vehicles to an extent of 14-20 The fuel savings themselves can support a large programme of concreting

Cement concrete roads save a substantial quantity of stone aggregates and this factor must be considered when a choice pavements is made Concrete roads can withstand extreme weather conditions ndash wide rangingtemperatures heavy rainfall and water logging

Though cement concrete roads may cost slightly more than a flexible pavement initially they are economical when whole-life-costing is considered

Reduction in the cost of concrete pavements can be brought about by developing semiself- compacting concrete techniques and the use of closely spaced thin joints RampD efforts should be initiated in this area

TYPES OF CONCRETE PAVEMENTS

1 PLAIN CONCRETE OR SHORT PAVEMENT SLABS

This type of pavement consists of successive slabs whose length is limited to about 25 times the slab thickness At present it is recommended that the paving slabs not be made longer than 5 even if the joints have dowels to transfer the loads The movements as a result of fluctuations in temperature and humidity are concentrated in the joints Normally these joints are sealed to prevent water from penetrating the road structure The width of the pavement slabs is limited to a maximum of 45 m

2 REINFORCED CONCRETE Continuously reinforced concrete-Continuously reinforced concrete pavements are characterised by the absence of transverse joints and are equipped with longitudinal steel reinforcement The diameter of the reinforcing bars is calculated in such a way that cracking can be controlled and that the cracks are uniformly distributed (spacing at 1 to 3 m) The crack width has to remain very small ie less than 03 mmReinforced pavement slabsReinforced concrete pavement slabs are almost never used except for inside or outside industrial floors that are subjected to large loads or if the number of contraction joints has to be limitedSteel fibre concreteThe use of steel fibre concrete pavements is mainly limited to industrial floors However in that sector they are used intensively For road pavements steel fibre concrete can be used for thin or very thin paving slabs or for very specific application

Site Clearance

General Site clearing generally consists of the cutting andor taking down removal and disposal of everything above ground level including objects overhanging the area to be cleared such as tree branches except such trees vegetation structures or parts of structures and other things which are designated in the contract to remain or be removed by others to which the engineer directed to be left undisturbed The material to be cleared usually but not necessarily is limited to trees stumps logs brush undergrowth long grasses crops loose vegetable matter and structureThe entire road area shall be cleared as described above unless otherwise shown on the drawing andor directed by the engineer

Setting out The right of way (ROW) shall be surveyed and set out before any site clearance is cleared out Wooden pegs usually indicate the surveyed rights of ways Procedure for setting out 1 Fixing of centre line of alignment by using total station theodelite 2 Calculating curvature and refractures (for curves and embankment) by using

auto levels or dumpy level 3 To establish traverse bench mark (TBM) at required intervals adjacent to

alignments 4 Location of levels at major conflict junctions 5 To mark the longitudinal and cross sectional pavement structure 6 To make efficient minimum and desired sight distance at major conflicts

and terrain and also setting out of horizontal curves throughout the alignment was done by using theodolite and total survey station Steps involved in surveying

10487661048766 Benchmark 10487661048766 Temporary benchmark at regular intervals 10487661048766 Centre line marking 10487661048766 Road markings

10487661048766 Profile marking (for longitudinal and cross sectional structures) 10487661048766 Establishment of different levels providing gradients as per to design considering different factors like-

Surveying using dumpy level

Plants and equipments Site clearing of trees vegetation undergrowth bushes and minor structures are carried out by dozers and or hydraulic excavators Trees that cannot be felled by the aforesaid equipment shall be felled by using saws Major structures that cannot practically be cleared by hydraulic excavators andor dozers these demolitions can be carried out using pneumatic tools explosives andor otherspecialized equipment depending on the size and type of structures Before commencing explosive demolition all necessary permits and licenses will be obtained and a blasting plan detailing the size of charges locations of holes system of detonation and safety precaution will be forwarded to the engineer together with the request sheets

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

TYPES OF PAVEMENTS

There are various types of pavements depending upon the materials used a briefs description of all types is given here-

FLEXIBLE PAVEMENTS-

Bitumen has been widely used in the construction of flexible pavements for a long time This is the most convenient and simple type of construction The cost of construction of single lane bituminous pavement varies from 20 to 30 lakhs per km in plain areas In some applications however the performance of conventional bitumen may not be considered satisfactory because of the following reasons-

In summer season due to high temperature bitumen becomes soft resulting in bleeding rutting and segregation finally leading to failure of pavement

In winter season due to low temperature the bitumen becomes brittle resulting in cracking ravelling and unevenness which makes the pavement unsuitable for use

In rainy season water enters the pavement resulting into pot holes and sometimes total removal of bituminous layer

In hilly areas due to sub-zero temperature the freeze thaw and heave cycle takes place Due to freezing and melting of ice in bituminous voids volume expansion and contraction occur This leads to pavements failure

The cost of bitumen has been rising continuously In near future there will be scarcity of bitumen and it will be impossible to procure bitumen at very high costs

RIGID PAVEMENTS-

Rigid pavements though costly in initial investment are cheap in long run because of low maintenance costs There are various merits in the use of Rigid pavements (Concrete pavements) are summarized below-

Bitumen is derived from petroleum crude which is in short supply globally and the price of which has been rising steeply India imports nearly 70 of the petroleum crude The demand for bitumen in the coming years is likely to grow steeply far outstripping the availability Hence it will be in Indias interest to

explore alternative binders Cement is available in sufficient quantity in India and its availability in the future is also assured Thus cement concrete roads should be the obvious choice in future road programmes

Besides the easy available of cement concrete roads have a long life and are practically maintenance-free

Another major advantage of concrete roads is the savings in fuel by commercial vehicles to an extent of 14-20 The fuel savings themselves can support a large programme of concreting

Cement concrete roads save a substantial quantity of stone aggregates and this factor must be considered when a choice pavements is made Concrete roads can withstand extreme weather conditions ndash wide rangingtemperatures heavy rainfall and water logging

Though cement concrete roads may cost slightly more than a flexible pavement initially they are economical when whole-life-costing is considered

Reduction in the cost of concrete pavements can be brought about by developing semiself- compacting concrete techniques and the use of closely spaced thin joints RampD efforts should be initiated in this area

TYPES OF CONCRETE PAVEMENTS

1 PLAIN CONCRETE OR SHORT PAVEMENT SLABS

This type of pavement consists of successive slabs whose length is limited to about 25 times the slab thickness At present it is recommended that the paving slabs not be made longer than 5 even if the joints have dowels to transfer the loads The movements as a result of fluctuations in temperature and humidity are concentrated in the joints Normally these joints are sealed to prevent water from penetrating the road structure The width of the pavement slabs is limited to a maximum of 45 m

2 REINFORCED CONCRETE Continuously reinforced concrete-Continuously reinforced concrete pavements are characterised by the absence of transverse joints and are equipped with longitudinal steel reinforcement The diameter of the reinforcing bars is calculated in such a way that cracking can be controlled and that the cracks are uniformly distributed (spacing at 1 to 3 m) The crack width has to remain very small ie less than 03 mmReinforced pavement slabsReinforced concrete pavement slabs are almost never used except for inside or outside industrial floors that are subjected to large loads or if the number of contraction joints has to be limitedSteel fibre concreteThe use of steel fibre concrete pavements is mainly limited to industrial floors However in that sector they are used intensively For road pavements steel fibre concrete can be used for thin or very thin paving slabs or for very specific application

Site Clearance

General Site clearing generally consists of the cutting andor taking down removal and disposal of everything above ground level including objects overhanging the area to be cleared such as tree branches except such trees vegetation structures or parts of structures and other things which are designated in the contract to remain or be removed by others to which the engineer directed to be left undisturbed The material to be cleared usually but not necessarily is limited to trees stumps logs brush undergrowth long grasses crops loose vegetable matter and structureThe entire road area shall be cleared as described above unless otherwise shown on the drawing andor directed by the engineer

Setting out The right of way (ROW) shall be surveyed and set out before any site clearance is cleared out Wooden pegs usually indicate the surveyed rights of ways Procedure for setting out 1 Fixing of centre line of alignment by using total station theodelite 2 Calculating curvature and refractures (for curves and embankment) by using

auto levels or dumpy level 3 To establish traverse bench mark (TBM) at required intervals adjacent to

alignments 4 Location of levels at major conflict junctions 5 To mark the longitudinal and cross sectional pavement structure 6 To make efficient minimum and desired sight distance at major conflicts

and terrain and also setting out of horizontal curves throughout the alignment was done by using theodolite and total survey station Steps involved in surveying

10487661048766 Benchmark 10487661048766 Temporary benchmark at regular intervals 10487661048766 Centre line marking 10487661048766 Road markings

10487661048766 Profile marking (for longitudinal and cross sectional structures) 10487661048766 Establishment of different levels providing gradients as per to design considering different factors like-

Surveying using dumpy level

Plants and equipments Site clearing of trees vegetation undergrowth bushes and minor structures are carried out by dozers and or hydraulic excavators Trees that cannot be felled by the aforesaid equipment shall be felled by using saws Major structures that cannot practically be cleared by hydraulic excavators andor dozers these demolitions can be carried out using pneumatic tools explosives andor otherspecialized equipment depending on the size and type of structures Before commencing explosive demolition all necessary permits and licenses will be obtained and a blasting plan detailing the size of charges locations of holes system of detonation and safety precaution will be forwarded to the engineer together with the request sheets

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

explore alternative binders Cement is available in sufficient quantity in India and its availability in the future is also assured Thus cement concrete roads should be the obvious choice in future road programmes

Besides the easy available of cement concrete roads have a long life and are practically maintenance-free

Another major advantage of concrete roads is the savings in fuel by commercial vehicles to an extent of 14-20 The fuel savings themselves can support a large programme of concreting

Cement concrete roads save a substantial quantity of stone aggregates and this factor must be considered when a choice pavements is made Concrete roads can withstand extreme weather conditions ndash wide rangingtemperatures heavy rainfall and water logging

Though cement concrete roads may cost slightly more than a flexible pavement initially they are economical when whole-life-costing is considered

Reduction in the cost of concrete pavements can be brought about by developing semiself- compacting concrete techniques and the use of closely spaced thin joints RampD efforts should be initiated in this area

TYPES OF CONCRETE PAVEMENTS

1 PLAIN CONCRETE OR SHORT PAVEMENT SLABS

This type of pavement consists of successive slabs whose length is limited to about 25 times the slab thickness At present it is recommended that the paving slabs not be made longer than 5 even if the joints have dowels to transfer the loads The movements as a result of fluctuations in temperature and humidity are concentrated in the joints Normally these joints are sealed to prevent water from penetrating the road structure The width of the pavement slabs is limited to a maximum of 45 m

2 REINFORCED CONCRETE Continuously reinforced concrete-Continuously reinforced concrete pavements are characterised by the absence of transverse joints and are equipped with longitudinal steel reinforcement The diameter of the reinforcing bars is calculated in such a way that cracking can be controlled and that the cracks are uniformly distributed (spacing at 1 to 3 m) The crack width has to remain very small ie less than 03 mmReinforced pavement slabsReinforced concrete pavement slabs are almost never used except for inside or outside industrial floors that are subjected to large loads or if the number of contraction joints has to be limitedSteel fibre concreteThe use of steel fibre concrete pavements is mainly limited to industrial floors However in that sector they are used intensively For road pavements steel fibre concrete can be used for thin or very thin paving slabs or for very specific application

Site Clearance

General Site clearing generally consists of the cutting andor taking down removal and disposal of everything above ground level including objects overhanging the area to be cleared such as tree branches except such trees vegetation structures or parts of structures and other things which are designated in the contract to remain or be removed by others to which the engineer directed to be left undisturbed The material to be cleared usually but not necessarily is limited to trees stumps logs brush undergrowth long grasses crops loose vegetable matter and structureThe entire road area shall be cleared as described above unless otherwise shown on the drawing andor directed by the engineer

Setting out The right of way (ROW) shall be surveyed and set out before any site clearance is cleared out Wooden pegs usually indicate the surveyed rights of ways Procedure for setting out 1 Fixing of centre line of alignment by using total station theodelite 2 Calculating curvature and refractures (for curves and embankment) by using

auto levels or dumpy level 3 To establish traverse bench mark (TBM) at required intervals adjacent to

alignments 4 Location of levels at major conflict junctions 5 To mark the longitudinal and cross sectional pavement structure 6 To make efficient minimum and desired sight distance at major conflicts

and terrain and also setting out of horizontal curves throughout the alignment was done by using theodolite and total survey station Steps involved in surveying

10487661048766 Benchmark 10487661048766 Temporary benchmark at regular intervals 10487661048766 Centre line marking 10487661048766 Road markings

10487661048766 Profile marking (for longitudinal and cross sectional structures) 10487661048766 Establishment of different levels providing gradients as per to design considering different factors like-

Surveying using dumpy level

Plants and equipments Site clearing of trees vegetation undergrowth bushes and minor structures are carried out by dozers and or hydraulic excavators Trees that cannot be felled by the aforesaid equipment shall be felled by using saws Major structures that cannot practically be cleared by hydraulic excavators andor dozers these demolitions can be carried out using pneumatic tools explosives andor otherspecialized equipment depending on the size and type of structures Before commencing explosive demolition all necessary permits and licenses will be obtained and a blasting plan detailing the size of charges locations of holes system of detonation and safety precaution will be forwarded to the engineer together with the request sheets

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

TYPES OF CONCRETE PAVEMENTS

1 PLAIN CONCRETE OR SHORT PAVEMENT SLABS

This type of pavement consists of successive slabs whose length is limited to about 25 times the slab thickness At present it is recommended that the paving slabs not be made longer than 5 even if the joints have dowels to transfer the loads The movements as a result of fluctuations in temperature and humidity are concentrated in the joints Normally these joints are sealed to prevent water from penetrating the road structure The width of the pavement slabs is limited to a maximum of 45 m

2 REINFORCED CONCRETE Continuously reinforced concrete-Continuously reinforced concrete pavements are characterised by the absence of transverse joints and are equipped with longitudinal steel reinforcement The diameter of the reinforcing bars is calculated in such a way that cracking can be controlled and that the cracks are uniformly distributed (spacing at 1 to 3 m) The crack width has to remain very small ie less than 03 mmReinforced pavement slabsReinforced concrete pavement slabs are almost never used except for inside or outside industrial floors that are subjected to large loads or if the number of contraction joints has to be limitedSteel fibre concreteThe use of steel fibre concrete pavements is mainly limited to industrial floors However in that sector they are used intensively For road pavements steel fibre concrete can be used for thin or very thin paving slabs or for very specific application

Site Clearance

General Site clearing generally consists of the cutting andor taking down removal and disposal of everything above ground level including objects overhanging the area to be cleared such as tree branches except such trees vegetation structures or parts of structures and other things which are designated in the contract to remain or be removed by others to which the engineer directed to be left undisturbed The material to be cleared usually but not necessarily is limited to trees stumps logs brush undergrowth long grasses crops loose vegetable matter and structureThe entire road area shall be cleared as described above unless otherwise shown on the drawing andor directed by the engineer

Setting out The right of way (ROW) shall be surveyed and set out before any site clearance is cleared out Wooden pegs usually indicate the surveyed rights of ways Procedure for setting out 1 Fixing of centre line of alignment by using total station theodelite 2 Calculating curvature and refractures (for curves and embankment) by using

auto levels or dumpy level 3 To establish traverse bench mark (TBM) at required intervals adjacent to

alignments 4 Location of levels at major conflict junctions 5 To mark the longitudinal and cross sectional pavement structure 6 To make efficient minimum and desired sight distance at major conflicts

and terrain and also setting out of horizontal curves throughout the alignment was done by using theodolite and total survey station Steps involved in surveying

10487661048766 Benchmark 10487661048766 Temporary benchmark at regular intervals 10487661048766 Centre line marking 10487661048766 Road markings

10487661048766 Profile marking (for longitudinal and cross sectional structures) 10487661048766 Establishment of different levels providing gradients as per to design considering different factors like-

Surveying using dumpy level

Plants and equipments Site clearing of trees vegetation undergrowth bushes and minor structures are carried out by dozers and or hydraulic excavators Trees that cannot be felled by the aforesaid equipment shall be felled by using saws Major structures that cannot practically be cleared by hydraulic excavators andor dozers these demolitions can be carried out using pneumatic tools explosives andor otherspecialized equipment depending on the size and type of structures Before commencing explosive demolition all necessary permits and licenses will be obtained and a blasting plan detailing the size of charges locations of holes system of detonation and safety precaution will be forwarded to the engineer together with the request sheets

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

This type of pavement consists of successive slabs whose length is limited to about 25 times the slab thickness At present it is recommended that the paving slabs not be made longer than 5 even if the joints have dowels to transfer the loads The movements as a result of fluctuations in temperature and humidity are concentrated in the joints Normally these joints are sealed to prevent water from penetrating the road structure The width of the pavement slabs is limited to a maximum of 45 m

2 REINFORCED CONCRETE Continuously reinforced concrete-Continuously reinforced concrete pavements are characterised by the absence of transverse joints and are equipped with longitudinal steel reinforcement The diameter of the reinforcing bars is calculated in such a way that cracking can be controlled and that the cracks are uniformly distributed (spacing at 1 to 3 m) The crack width has to remain very small ie less than 03 mmReinforced pavement slabsReinforced concrete pavement slabs are almost never used except for inside or outside industrial floors that are subjected to large loads or if the number of contraction joints has to be limitedSteel fibre concreteThe use of steel fibre concrete pavements is mainly limited to industrial floors However in that sector they are used intensively For road pavements steel fibre concrete can be used for thin or very thin paving slabs or for very specific application

Site Clearance

General Site clearing generally consists of the cutting andor taking down removal and disposal of everything above ground level including objects overhanging the area to be cleared such as tree branches except such trees vegetation structures or parts of structures and other things which are designated in the contract to remain or be removed by others to which the engineer directed to be left undisturbed The material to be cleared usually but not necessarily is limited to trees stumps logs brush undergrowth long grasses crops loose vegetable matter and structureThe entire road area shall be cleared as described above unless otherwise shown on the drawing andor directed by the engineer

Setting out The right of way (ROW) shall be surveyed and set out before any site clearance is cleared out Wooden pegs usually indicate the surveyed rights of ways Procedure for setting out 1 Fixing of centre line of alignment by using total station theodelite 2 Calculating curvature and refractures (for curves and embankment) by using

auto levels or dumpy level 3 To establish traverse bench mark (TBM) at required intervals adjacent to

alignments 4 Location of levels at major conflict junctions 5 To mark the longitudinal and cross sectional pavement structure 6 To make efficient minimum and desired sight distance at major conflicts

and terrain and also setting out of horizontal curves throughout the alignment was done by using theodolite and total survey station Steps involved in surveying

10487661048766 Benchmark 10487661048766 Temporary benchmark at regular intervals 10487661048766 Centre line marking 10487661048766 Road markings

10487661048766 Profile marking (for longitudinal and cross sectional structures) 10487661048766 Establishment of different levels providing gradients as per to design considering different factors like-

Surveying using dumpy level

Plants and equipments Site clearing of trees vegetation undergrowth bushes and minor structures are carried out by dozers and or hydraulic excavators Trees that cannot be felled by the aforesaid equipment shall be felled by using saws Major structures that cannot practically be cleared by hydraulic excavators andor dozers these demolitions can be carried out using pneumatic tools explosives andor otherspecialized equipment depending on the size and type of structures Before commencing explosive demolition all necessary permits and licenses will be obtained and a blasting plan detailing the size of charges locations of holes system of detonation and safety precaution will be forwarded to the engineer together with the request sheets

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Site Clearance

General Site clearing generally consists of the cutting andor taking down removal and disposal of everything above ground level including objects overhanging the area to be cleared such as tree branches except such trees vegetation structures or parts of structures and other things which are designated in the contract to remain or be removed by others to which the engineer directed to be left undisturbed The material to be cleared usually but not necessarily is limited to trees stumps logs brush undergrowth long grasses crops loose vegetable matter and structureThe entire road area shall be cleared as described above unless otherwise shown on the drawing andor directed by the engineer

Setting out The right of way (ROW) shall be surveyed and set out before any site clearance is cleared out Wooden pegs usually indicate the surveyed rights of ways Procedure for setting out 1 Fixing of centre line of alignment by using total station theodelite 2 Calculating curvature and refractures (for curves and embankment) by using

auto levels or dumpy level 3 To establish traverse bench mark (TBM) at required intervals adjacent to

alignments 4 Location of levels at major conflict junctions 5 To mark the longitudinal and cross sectional pavement structure 6 To make efficient minimum and desired sight distance at major conflicts

and terrain and also setting out of horizontal curves throughout the alignment was done by using theodolite and total survey station Steps involved in surveying

10487661048766 Benchmark 10487661048766 Temporary benchmark at regular intervals 10487661048766 Centre line marking 10487661048766 Road markings

10487661048766 Profile marking (for longitudinal and cross sectional structures) 10487661048766 Establishment of different levels providing gradients as per to design considering different factors like-

Surveying using dumpy level

Plants and equipments Site clearing of trees vegetation undergrowth bushes and minor structures are carried out by dozers and or hydraulic excavators Trees that cannot be felled by the aforesaid equipment shall be felled by using saws Major structures that cannot practically be cleared by hydraulic excavators andor dozers these demolitions can be carried out using pneumatic tools explosives andor otherspecialized equipment depending on the size and type of structures Before commencing explosive demolition all necessary permits and licenses will be obtained and a blasting plan detailing the size of charges locations of holes system of detonation and safety precaution will be forwarded to the engineer together with the request sheets

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

10487661048766 Profile marking (for longitudinal and cross sectional structures) 10487661048766 Establishment of different levels providing gradients as per to design considering different factors like-

Surveying using dumpy level

Plants and equipments Site clearing of trees vegetation undergrowth bushes and minor structures are carried out by dozers and or hydraulic excavators Trees that cannot be felled by the aforesaid equipment shall be felled by using saws Major structures that cannot practically be cleared by hydraulic excavators andor dozers these demolitions can be carried out using pneumatic tools explosives andor otherspecialized equipment depending on the size and type of structures Before commencing explosive demolition all necessary permits and licenses will be obtained and a blasting plan detailing the size of charges locations of holes system of detonation and safety precaution will be forwarded to the engineer together with the request sheets

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Image Double barrel Asphalt Premix plant

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Image Aggregate Crusher

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Sequence of works Prior to the commencement of the site clearance the following shall be carried out either independently or jointly with the Engineerrsquos Representative

(I) The right of ways (ROW) shall be surveyed and set out according to the data stated in the drawings

(II) Photographs shall be taken of structures landscaping trees and shrubs fences telephone and electrical poles and other if they are payable under individual measured item apart from the general site clearance in the bill of quantities

(III) The above site clearance items shall be measured according to the method of measurement jointly with the Engineerrsquos Representatives The location of these items shall be identified according to the survey data or offsets from the centerline of the proposed alignment in road construction

(IV) Prior to demolition of existing buildings liaison with the respective authorities terminates the utilities supply to the building

(V) Removal of landscaping trees and shrubs shall be carried out with the prior approval of the concerned authority

(VI) Fencing or others that are to be relocated or salvaged shall be carried out according to the drawings or as per the instructions given by Engineer

(VII) Obtain confirmation that the employer or relevant authority have acquired the right of way lands

(VIII) Access roads to the site shall be constructed if required to enable vehicles equipment and plants to be brought in it

(IX) Solid waste dumps sites shall be predetermined within or outside the site for the dumping of the site clearing materials

(X) The site clearance then shall be proceeded to clear the trees vegetation undergrowth bushes and minor structures by hydraulic excavators or dozers

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Filling For Embankment

Construction method The embankment shall be constructed to the level heights widths and slopes shown on the drawing with following procedures General The area to receive fill shall be sampled and tested below topsoil in accordance with the specification If the test results indicate that the material is for suitable to receive fill then a request of Approval starting compaction of existing ground will be submitted Before starting the compaction of the existing ground the topsoil will be stripped from the area either to a thickness agreed from the soil sampling holes or as directed on site by the Engineer or his designated staff and afterwards measured by leveling After compacting the existing ground to specified standard density tests will be carried out and a Request for Approval to start filling will be submitted Where it is the intention to commence filling will be commence by cutting to firm material for cross fill

Fill materials for use in forming embankments shall be suitable material obtained from excavation cuttings or borrow pits

Prior to commencement of the works the selected sample from the source of cutting or borrow pits shall be sent for laboratory test

Trial compaction shall be carried out at the designated area of the site to determine the pattern of compaction for type of material to be used This shall include the use of compaction plant and the number of passes in relation to the loose depth of material to achieve desired compaction The approximate quantity of water required per unit area to bring the fill close enough to the Optimum Moisture Content to achieve the specified compaction standard economically shall be computed and thereafter uniformly mixed throughout the material depth and width to be compacted

After the required passes for compaction has been accepted the filling shall be carried out in layer not exceeding 200 mm compacted depth and shall be compacted by the compaction plant as used and achieved in the trial areas

The density test shall be carried out in every compacted layer of approx 200 mm depth and the Nos of test shall be done in accordance with the MORTampH specification

The Engineerrsquos Site representative will witness the test and the result sent to the Engineer for approval to proceed further with next layer

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

On the fill slope the filling shall be in layer and with extended extra width for cut back to form the compacted slope

Prior to the commencement of massive cutfill the haul roads shall be constructed with sufficient width for to and fro traffic and to ensure smooth movement of the plant

Excavators shall be deployed for excavation and loading the cut material on the dump trucks for filling At the filling area the dump trucks transport the material to the spread spot and tip from one end One bulldozer or grader shall be used for spreading the material into loose layers to the thickness indicated by the compacted thickness or less Water shall be spread and mixed in as required until the whole layer is of one uniform moisture content and the vibrating roller shall be used for compacting the layer Field Density tests shall carry out and if the results indicate compliance with the specification then a Request for Approval to place the next layer will be submitted The slope trimming shall be completed after the pavement and shoulders are completed

The trimmed slope is to be turned if specified

Subsoil drainGeneral This work shall include the supply and installation of subsoil drains constructed in accordance with the contract specification at the locations and in accordance with the lines levels and grades as shown on the drawings and or as directed by the Engineer Materials Concrete pipes ar polyvinyl chloride (PVC) pipes for the subsoil drains shall comply with the relevant contract specification

Filter material used in the construction of subsoil drains shall consist of hard clean crushed rock or gravel having a grading limits given in the specification The aggregate crushing value of the material shall not exceed 30

The filler cloth shall be geotextile fabric as specified in the contract

Construction method Excavation of longitudinal and cross trenches shall be carried out all in accordance with the approximate provisions of specification and drawings At the completion of excavation Request for Approval forms for placing filter materials will be submitted to the Engineer

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Filter cloth shall then be placed to cover the perimeter of the longitudinal trench excavated with the top open to facilitate the placement of filter material Subsoil cross pipe is then laid in the cross trench at minimum 1 slope with the inlet face covered with filter cloth and the outlet being free outfall The inlet of cross pipe is to be imbedded in the filter material fill placed in the longitudinal trench Care shall be taken against damage of filter cloth during the construction stage Filter material shall be placed in longitudinal trench and uniformly compacted The filter cloth shall be closed at top and backfilled with soil At the completion of placing filter materials a Request for Approval for placing compacted backfill will be submitted During backfilling random field density check tests will be carried out

Granular Sub-BaseGeneral Sub base is the lowest of all the pavement layers consisting of natural sand mooram gravel crushed stone or combination thereof necessary to comply with the grading requirements of Table 400-1 Grading I Materials Prior to the laying of sub base a Request for Approval of Material shall be submitted which will indicate compliance with the specified properties of sub base material

Fraction of material passing the 224 mm sieve shall have a soaked CBR of 30 or greater

The fraction passing the 0425 mm sieve shall have Liquid Limit not greater than 25 and a Plasticity Index not greater than 6

The soaked 10 fines value (KN) shall be greater than 50 If the water absorption is greater than 2 the Soundness Test IS 383 shall

be carried out The grading shall be as follows

SEIVE SIZE (MM) PERCENTAGE PASSING 75 100 53 80-100 265 55-90 95 35-65 475 25-55 236 20-40 0425 10-25 0075 3-10

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Laying equipment

The following plants are required for the laying of sub-base-

(i) Motor Grader(ii) Tipper Trucks(iii) Vibratory Roller(iv) Water Tanker

Wet Mix Macadam

General

Wet mix macadam (WMM) is a base material in road pavement structure which is batched from a mixing plant and laid in position with a paver Materials WMM consists of crushed graded aggregate and granular material pre mixed with water Equipments

Constructional plants required are as follows-

A) WMM MIXING PLANT

1

B) PAVER 1

C) MOTOR GRADER 1

D) VIBRATORY ROLLER

1

E) TIPPER 3

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Procedures Work shall commence on site upon Approval and Acceptance of the sub-base layer The wet mix macadam shall be plant mixed with moisture content within reasonable limits of the Optimum Moisture Value as determined in accordance with IS 2720 (Part 8)

The approved wet mix macadam shall be delivered to site by tipper trucks To prevent the loss of moisture the materials shall be covered if necessary

(i) The wet mix macadam shall be laid by using a paving machine(ii) Segregation at localized areas shall be made good by back casting

with fines or by immediate removal and replacement of the freshly laid wet mix macadam

(iii) Transverse joint shall be lapped and longitudinal joints due to stoppage of work will have the loose removed before paving resumes

(iv) Compaction shall be carried out using vibratory roller and as per specifications

(v) The surface of the wet mix macadam shall be finished to the grade and line as required by the drawings and within specified tolerance limits

(vi) On completion of laying and compaction approval of the Engineer will be obtained for compliance with the specified requirement before proceeding with the next layer

(vii) Sampling of mixture shall be carried out at the plant or site

MINERALS USED

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Concrete is widely used in domestic commercial recreational rural and educational construction Communities around the world rely on concrete as a safe strong and simple building material It is used in all types of construction from domestic work to multi-storey office blocks and shopping complexes Despite the common usage of concrete few people are aware of the considerations involved in designing strong durable high quality concreteThere are mainly three materials used primarily-CementSandAggregate

CEMENT

Cement is a binder a substance that sets and hardens independently and can bind other materials together The word cement traces to the Romans who used the term caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum cimentum cement and cement Cements used in construction can be characterized as being either hydraulic or nonhydraulic Hydraulic cements (eg Portland cement) harden because of hydration a chemical reaction between the anhydrous cement powder and water Thus they can harden underwater or when constantly exposed to wet weather The chemical reaction results in hydrates that are not very water-soluble and so are quite durable in water Non-hydraulic cements do not harden underwater for example slaked limes harden by reaction with atmospheric carbon dioxide The most important uses of cement are as an ingredient in the production of mortar in masonry and of concrete a combination of cement and an aggregate to form a strong building material

TYPES OF CEMENT-

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Portland cementPortland cement is by far the most common type of cement in general use around the world This cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 degC in a kiln in a process known as calcinations whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide or quicklime which is then blended with the other materials that have been included in the mix The resulting hard substance called clinker is then ground with a small amount of gypsum into a powder to make Ordinary Portland Cement the most commonly used type of cement (often referred to as OPC) Portland cement is a basic ingredient of concrete mortar and most non-specialty grout The most common use for Portland cement is in the production of concrete Concrete is a composite material consisting of aggregate (gravel and sand) cement and water As a construction material concrete can be cast in almost any shape desired and once hardened can become a structural (load bearing) element Portland cement may be grey or white

Portland fly ash cementIt contains up to 35 flyash The fly ash is pozzolanic so that ultimate strength is maintained Because fly ash addition allows lower concrete water content early strength can also be maintained Where good quality cheap fly ash is available this can be an economic alternative to ordinary Portland cement

Portland pozzolana cementIts includes fly ash cement since fly ash is a pozzolana but also includes cements made from other natural or artificial pozzolans In countries where volcanic ashes are available

Portland silica fume cementAddition of silica fume can yield exceptionally high strengths and cements containing 5ndash 20 silica fume are occasionally produced However silica fume is more usually added to Portland cement at the concrete mixer

SAND

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles The composition of sand is highly variable depending on the local rock sources and conditions but the most common constituent of sand in inland continental settings and nontropical coastal settings is silica (silicon dioxide or SiO2) usually in the form of quartz The second most common type of sand is calcium carbonate for example aragonite which has mostly been created over the past half billion years by various forms of life like coral and shellfish It is for example the primary form of sand apparent in areas wherereefs have dominated the ecosystem for millions of years like the Caribbean

AGGREGATE

Aggregates are inert granular materials such as sand gravel or crushed stone that along with water and Portland cement are an essential ingredient in concrete For a good concrete mix aggregates need to be clean hard strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete Aggregates which account for 60 to 75 percent of the total volume of concrete are divided into two distinct categories-fine and coarse Fine aggregates generally consist of natural sand orcrushed stone with most particles passing through a 38-inch (95-mm) sieve Coarse aggregates are any particles greater than 019 inch (475 mm) but generally range between 38 and 15 inches (95 mm to 375 mm) in diameter Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder Natural gravel and sand are usually dug or dredged from a pit river lake or seabed Crushed aggregate is produced by crushing quarry rock boulders cobbles or large-size gravel Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular sub bases soil-cement and in new concrete Aggregate processing consists of crushing screening and washing the aggregate to obtain proper cleanliness and gradation If necessary a benefaction process such as jigging or heavy media separation can be used to upgrade the qualityOnce processed the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination Aggregates strongly influence concretes freshly mixed and hardened properties mixture proportions and economy Consequently selection of aggregates is an important process Although some variation in aggregate properties is expected characteristics that are considered when selecting aggregate include-gradingdurabilityparticle shape and surface texture

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

abrasion and skid resistanceunit weights and voidsabsorption and surface moisture Grading refers to the determination of the particle-size distribution for aggregate Grading limits and maximum aggregate size are specified because grading and size affect the amount of aggregate used as well as cement and water requirements workability

FINE AGGREGATE

Fine aggregate shall consist of sand or sand stone with similar characteristics or combination thereof It shall meet requirements of the State Department of Transportation of Uttar Pradesh Section 501363 of the Standard Specifications for Highway and Structure Construction current edition

COARSE AGGREGATE

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Coarse aggregate shall consist of clean hard durable gravel crushed gravel crushed boulders or crushed stone It shall meet the requirements of the State Department of Transportation of Uttar Pradesh Section 501364 of the Standard Specifications for Highway and Structure Construction current edition

Aggregate EquationPROPORTIONING

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

The following table sets forth the master limits of the job mix for the several grades of concrete and designates the quantities of materials and relative proportions for each grade of concrete For Air-Entrained High-Early-Strength Concrete as required or permitted when High-Early-Strength Cement is used the proportions shall be as given in the table The quantities of aggregates set forth in the tabulations are for oven dry materials having a bulk specific gravity of 265 For aggregates having a different specific gravity the weights shall be adjusted in the ratio that the specific gravity of the material used bears to 265

PROCEDURE TO CONSTRUCT PAVEMENTS

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

During construction of a cement concrete pavement various steps are taken as below-

Survey of proposed work is done by experienced engineers or by any expert of survey site survey includes geographical details soil properties and site investigationAfter survey a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft waresAfter that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirementsNow excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal processAnd after these construction of soil sub grade base coarse and then construction of concrete slab is done

PREPARATION OF THE SUB- GRADE OR BASECOARSE

The road sub grade has to be prepared carefully in order to realize everywhere a pavement structure of an adequate and uniform thickness This allows to provide a homogeneous bond between the concrete slab and its foundation which is important for the later behaviour of the pavement structureFor roads with a base drainage of the water must be provided Mud leaves etc have to be removed When the base is permeable it should be sprayed with water in order to prevent the mixing water from being sucked out of the concrete However if the base is impermeable (eg if the concrete is placed on a watertight asphalt concrete interlayer) it can be necessary under warm weather conditions to cool down this layer by spraying water on the surface The following points are important for roads without a foundationDrainage of all surface waterGood compaction of the sub gradeFilling and compaction of any ruts caused by construction trafficIt is forbidden to level the sub grade by means of a course of sand If the sub grade has to be levelled it is advisable to do this by using a granular material either slag or coarse aggregate eg with a grain size 020Provide an additional width of the sub grade for more lateral support It must always be avoided that water is sucked from the cement paste into the substructure or the base This can be accomplished by either moderately moistening the sub grade or by applying a plastic sheet on the substructure of

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

the pavement The latter work must be done with care to prevent the sheet from tearing or being pulled loose by the wind

MIXING AND TRANSPORT OF CONCRETECONCRETE MIXING PLANT

The concrete mixing plant must have a sufficient capacity in order to be able to continuously supply concrete to the paving machines The mix constituents and admixtures have to be dosed very accurately The number of aggregate feed bins has to equal at least the number of different aggregate fractions The bins shall have raised edges to prevent contamination of the aggregate fractions The equipment for loading the materials shall be in good condition and shall have sufficient capacity to be able to continuously feed the bins The bucket of theloaders shall not be wider than the bins The content of the cement silos and the water tank are in proportion to the production rates

For small works permanent concrete mixing plants are often called on In that case mixing plants that are inspected and that can deliver Indian quality certification concrete should be used Furthermore it is useful and even essential

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

to have a communication system between the concrete mixing plant and the construction site in order to coordinate the batching and paving operations

TRANSPORT OF THE CONCRETE

Sufficient trucks must be available to continuously supply the paving machines The number depends on the yield at the construction site the loading capacity of the trucks and the cycle time (ie the transport time plus the time required to load and unload a truck) The loading capacity and the type of truck to be used depend on the nature of the work the haul roads and the concrete paving machines Usually the specifications prescribe that the concrete has to be transported in dump trucks as paving concrete consists of a relatively dry mix having a consistency that makes transport and unloading in truck mixers difficult Furthermore dump trucks can discharge the concrete faster For small works and in urban areas the use of truck mixers is increasingly accepted Under these circumstances an admixture (eg a superplastisizer ) can be mixed in just before discharging the concrete The necessary measures have to be taken to prevent changes of the water content and temperature of the concrete during transport To this end the specifications prescribe to cover the dump trucks by means of a tarpaulin

PLACING THE CONCRETE

Usually the concrete is placed using slip form paving machines which applies for all categories of roads This equipment meets both the requirements for quality and for the envisaged rate of production Conventional concreting trains riding on set up rails are hardly used any more for roadworks in our country For this reason this manner of execution will not be dealt with here However the technique of manually placing the concrete using forms is still applied in certain cases such as for the construction of roundabouts with a small diameter at intersections for repair work or when the execution conditions are such that slip form pavers cannot be utilized This occurs increasingly often in urban areas for the construction of pavement surfaces of exposed aggregate and possibly coloured concrete

SLIP FORM CONCRETE PAVING

PREPARATION OF THE TRACK RUNWAY

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

The quality of the runway for the tracks of the paving equipment is undoubtedly one of the most important factors that contribute to the realisation of a smooth pavement surface In connection therewith the following criteria have to be met-sufficient bearing capacity so that the slip form paver can proceed without causing deformationsgood skid resistance to prevent the tracks from slipping especially when paving on a slopegood evenness to avoid that the self-levelling systems have to compensate forexcessive differences in height The track runway is a determining factor for thesteering and consequently its surface has to at least as smooth as the concrete paving surface itself The runway surface has to be permanently cleaned prior to the passage of the tracks

The track runway has to be wide enough taking into account

the greatest width of the paving machine plus an extra width (especially onembankments)the necessary space for placing the sensor lines

EXECUTION

The supply of the concrete has to be arranged in such a way that a continuous placement can be guaranteed without detrimental interruptions as each standstill

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

can cause unevennesss This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete

The concrete is dischargedeither directly in front of the machine using dump trucks The concrete must be discharged gradually in order to limit the drop height A crane is often necessary especially for larger working widths in order to adequately spread the concrete mixor in the bin of a side feeder for example if transport by dump trucks on thefoundation is impossible because of the presence of dowel chairs or reinforcement steelor in a supply container from which the concrete is scooped with a craneIt cannot be overemphasised that properly spreading the concrete in front of the slip form paving machine is very important for the final quality of the work especially with regard to the smoothness It is of great importance that in front of the slip form paver a constant and sufficient amount of concrete is available at all times so that a continuous paving process can be guaranteed The paver should never be used to push the concrete forward For large casting widths the concrete is preferably spread either by means of a placerspreader machine that operates in front of the paver or by the slip form paver itself (side feeder spreading augers wagonhellip) The use of a placerspreader allows the slip form paver to proceed more steadily The distance between the placerspreader and the slip form machine has to be kept small enough to limit changes in the water content of the concrete mix

The paving rate has to match the concrete delivery rate but the consistency of the concrete and the evenness of the track runways must also be taken into consideration In practice the optimum speed of the paving machine lies between 075 and 1 mmin A steady progress of the paving operations without detrimental interruptions guarantees quality whatever type of machine is used

All regulating devices of the paving machine have to be tuned before any paving is started However this regulation should also be monitored during the entire course of the paving process and adjusted if necessary so that the concrete pavement is executed correctly thickness flawless edges surface smoothnessSome machines are equipped with a dowel bar inserter or an anchor bar (also called tie-bar) inserter Dowel bars are inserted in the fresh concrete down to the correct elevation after the vibrator but before the tamper bar The dowel bar inserter preferably operates in a continuous

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

operation Every precaution must be taken to place the dowels correctly and not to disrupt the evenness of the concrete surface (composition of the concrete paving speed etc) The use of a super smoother (longitudinal floating tool) is highly recommended and in some specifications it is even made compulsory whenever a slip form paver is used and especially for pavements for high speed roads The super smoother is a beam float suspended from the backside of the slip form machine and that moves back and forth in the longitudinal direction while simultaneously traversing the freshly finished concrete surface It allows to eliminate small finishing errors or any remaining high and low spots behind the slip form paver This improves the driving comfort and limits the nuisance caused by unevennesss with a short wave length (noise vibrations) Small traces of cement slurry produced after the passage of the super smoother are subsequently removed by dragging a section of burlap or a drag plate The super smoother can also be used for other road categories including bicycle paths

MEASURES TO OBTAIN A GOOD EVENNESS

A good evenness depends primarily on the following factors-A concrete mix with an uniform consistency adapted to the paving machines and the working circumstancesA regular supply of concrete and a uniform spreading in front of the paverCorrect operation of the paving machines which in turn depends on the setting of the forms or the sensor lines the quality of the track runways the regulation of the sensors etcSteady progress of the paver without interruptions and with a speed compatible with the consistency of the concrete and the working circumstancesuse of specific tools or equipment to eliminate small bumps after the paving machines correction beam super smoother etc

EXECUTION OF JOINTS

All the equipment that is necessary to make joints in the fresh or hardened concrete must be present at the construction site The saw blades have to be

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

suitable to the quality of the concrete ie to the hardness and the abrasion resistance of the aggregates It is useful to have spare equipment available in case of a defect The beam for making a construction joint shall be rigid and shall allow the realization of a straight joint perpendicular to the axis of the road This beam has to be adapted to the type of pavement (jointed pavement continuously reinforced concrete pavement)

TRANSVERSE JOINTS-

1 CONTRACTION JOINTS

Crack onsets are executed to avoid uncontrolled (ldquowildrdquo) cracking of the concrete by shrinkage Contraction joints have a crack onset which extends to a depth of one third of the slab thickness and can be equipped with dowels On main roads the contraction joints are usually made by sawing The saw cutting should occur as soon as possible usually between 5 and 24 hours after placement of the concrete It is obvious that the concrete should have hardened sufficiently in order to prevent the edges of the joint from being damaged In case of high temperatures special equipment is available to execute saw cutting within 3 hours subsequent to the placement of the concrete In that case light equipment is used to make saw cuts of about 25 cm deep Every saw cut that has not instigated a crack within 24 hours is deepened up to 13 of the slab thickness Making crack onsets for contraction joints in the fresh concrete is a technique that is practically no longer applied except for country roads or municipal roads whenever the traffic intensity and evenness requirements permit so To make such a joint a thin steel blade (no more than 6 mm thick) is vibrated into the fresh concrete to a depth of 13 of the slab thickness The joint can be made both with flexible and with rigid joint strips In the first method a thin plastic strip twice as wide as the depth of the crack point plus 2 cm is laid on the fresh concrete The steel blade is positioned in the middle of the strip and is subsequently vibrated into the fresh concrete In the second method the rigid joint strip is inserted into a groove priory made by vibrating the steel blade in the concrete The top of the strip must be flush with the pavement surfaceAfter having made the crack onset the concrete surface along the joint should be smoothened again However manual corrections should be kept to a minimum as much as possible since they can cause spalling of the joint edges later

2 EXPANSION JOINTS

Expansion joints are only used exceptionally In these rare cases they have to meet the necessary requirements so as not to cause difficulties later

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

The execution of expansion joints requires special attention when using slip form paving machines

Special attention shall be paid to the following

The wooden joint filler board shall be firmly attached to the base by means of metal stakes so that it cannot move while the concrete is being placedThe height of the joint filler board shall be slightly(2 to 3 cm) shallower than the thickness of the concrete slab in order not to hinder the placement of the concrete As soon as the slip form paving machine has passed the concrete above the joint filler board shall be removed over a width at least equal to the thickness of the board so that no ldquoconcrete archrdquo is made at the top of the jointExpansion joints shall always be provided with dowels even for roads with less intense traffic At one end of each dowel a cap filled with a compressible material accommodates the movements of the concrete

3 CONSTRUCTION JOINTS

Construction joints also called end-of-day or working joints - are made at the end of the daily production or when the paving process is interrupted for at least 2 hours The face of these joints is plane vertical and perpendicular to the axis of the pavement They are always doweled Upon resuming the paving the fresh concrete is placed against the concrete that has already hardened The concrete is consolidated on both sides of the joint with a separate manual needle vibrator

LONGITUDINAL JOINTS

Longitudinal joints run parallel to the axis of the road and are only necessary if the pavement is wider than 45m They can be provided with tie bars

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

1 LONGITUDINAL CONTRACTION BENDING JOINTS

These joints are realised between adjacent concrete lanes that are executed simultaneously They are saw cut in the hardened concrete no later than 24 hours after the concrete has been placed The depth is at least 13 of the thickness of the slab

2 LONGITUDINAL CONSTRUCTION JOINTS

These are joints between two adjacent concrete lanes that are executed successively

CURING

Curing is the process of increasing hydration in cement after setting the concrete curing process is done till 20 to 25 days

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

There are some method of curing-

Shading concrete worksCovering with hessian amp gunny bagsSprinkling of waterBy pondingMembrane curing

PROTECTION OF THE CONCRETE PAVEMENT

1 PROTECTION AGAINST DRYING OUT

The quality of hardened concrete and in particular the durability of the surface depends directly on the protection of the fresh concrete against drying out It is detrimental both to the strength and to the shrinkage (risk of cracks forming) and also to the durability when the fresh concrete loses water As a result of their large exposed areas pavements are greatly subjected to drying out Eg at an ambient temperature of 20degC a relative humidity of 60 a temperature of the concrete of 25degC and a wind speed of 25 kmh 1 litre of water will evaporate every hour from every m2of pavement surface Note that the upper surface layer (a few cm thick) of the concrete only contains about 4 litres of water per m2

A curing compound is usually used to protect road concrete against drying out This coating is sprayed on the concrete top surface and on the vertical surfaces immediately after the paving train has passed and if applicable after the

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

concrete surface has been broomed In case of an exposed aggregate finish the setting retarder must also have the property that it protects the concrete against drying out If not the concrete must be covered with a plastic sheet as soon as the setting retarder is applied As stated above subsequent to the removal ofthe skin of concrete mortar the concrete is protected against drying out a second time by spraying a curing compound or by covering the surface with a plastic sheet The latter method is particularly used in urban areas on coloured exposed aggregate concrete The curing compound has to be applied at a rate of at least 200 gm2 and its effectiveness coefficient shall be greater than 80 Curing compounds are pigmented white or have a metallic gloss so as to better reflect sunlight which limits the warming up of the concrete

2 PROTECTION AGAINST RAIN

Concreting is stopped if it rains Furthermore the necessary measures have to be taken to prevent that the concrete surface is washed out by rain This applies both to freshly spread concrete that has not been compacted yet and to smoothed concrete Plastic sheets or mobile shelters are suitable means of protection

3 PROTECTION AGAINST FROST

When concrete is placed in cold weather (see also sect 841) the pavement surface has to be effectively protected against frost in such a way that the temperature at the surface of the concrete does not drop below + 1 ordmC for 72 hours after placement This protection can consist of for example non-woven geotextile or polystyrene foam plates with ballast

4 PROTECTION AGAINST MECHANICAL INFLUENCES(TRAFFIC SIGNPOSTING)

Every necessary measure shall be taken to protect the fresh concrete from damage due to all kinds of mechanical influences (cars bicycles pedestrians animals etc)

In urban areas these measures are even more necessary

SPECIAL MEASURES

WORKABILITY PERIOD

It must always be ensured that the concrete is processed as quickly as possible certainly within 2 hours after batching including the surface treatment and the

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

protection measures In hot dry weather an even shorter workability time has to be observed (maximum 90 minutes) Unless special precautions are taken that have been approved by the manager of the works concrete can only be laid if the air temperature at 15 m above ground under thermometershelter does not exceed 25degc Furthermore all necessary measures shall be taken to keep the water content of the concrete as constant as possible from the time of batching until completion of the placement

PAVING INTERRUPTIONS

Whenever the supply of concrete is interrupted the driver of the paving machine shall immediately take the necessary measures to lower the speed of the paving train and to ensure that the machine stops as little as possible For a short interruption the machine should be stopped before the deposited concrete in the vibrating chamber has dropped to such a level that the vibrators become visible If the supply is interrupted for more than 60 minutes (45 min in hot weather) a construction joint has to be made Upon a long-lasting defect of the paving equipment the supply of fresh concrete has to be stopped immediately and an attempt must be made to complete the current paving phase If the circumstances and the elapsed workability time no longer make a proper completion possible the concrete that has been deposited but not yet finished has to be removed To achieve a continuous profile particular care is taken of the execution of the construction joints both at the end of the day and every time work is resumed The concrete is compacted preferably with a separate vibrating needle before the paving machine is passing in order to obtain properly compacted concrete on both sides of the joint

PLACEMENT OF CONCRETE ON A SLOPE

When placing concrete on a slope of less than 4 it is recommended to work uphill in order to prevent tension cracks at the surface Furthermore the consistency of the concrete and the working speed of the paver have to be adapted to the working conditions However if the longitudinal slope is more than 4 unevenness can occur as concrete falls back when the machines have passed In that case a suitable composition of the concrete mix has to be realized and it is recommended to work downhill It must be ensured that enough concrete is deposited in front of the paving machine to prevent the concrete from sliding down Concrete pavements have been successfully executed on slopes of 10 to 12 At one time the slope was even 18

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

OPENING TO TRAFFIC

Usually a concrete pavement is only opened to traffic 7 days after the concrete has been laid and after in the presence of all parties any possible cracks have

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

been recorded A concrete pavement of less than 7 days old can be opened to traffic if the contractor provides proof that the concrete has reached the minimum compressive strength stipulated in the specifications Presently special compositions of the concrete mix allow an early opening to traffic iebetween 24 and 48 hours after placement These mixes are used for example for pavement repair works to reduce the nuisance to the public as much as possible It is pointless to talk about quality if not all employees each at his own level make a special effort to understand the rules of good practice upgrade their know-how and act accordingly

COST ANALYSIS OF RIGID PAVEMENTS

The selection criteria of type of pavement flexible or rigid should be based not on the initial cost of construction but life cycle cost which includes the discounted maintenance and pavement strengthening costs that are incurred during the design life of the pavement

INITIAL COST

This is the cost of construction of the pavement which mainly depends upon the pavement thickness governed by the strength of sub grade soil and traffic loading cost of materials and cost of execution of the work the above have a wide range of variability across the country and is difficult to generalise

MAINTENANCE COSTThe maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service levelIn case of rural roads maintenance of these roads is to be done by the respective state government from its available financial resources most of the states have poor past performance record to maintain such low volume roads through other schemes mainly because of having inadequate funds for maintenance of road infrastructure in the state

LIFE CYCLE COST ANALYSIS

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

Life cycle cost analysis can be defined as a procedure by which a pavement design alternative will be selected which will provide a satisfactory level of service at the lowest cost design life

RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PERKILOMETERSThe design of rigid pavement depends upon the CBR value of sub grade design axle load of commercial vehicles during the design life which is generally 20 years or more for rural roads a typical pavement composition for rural road is given below ( refer SP62-2004)

MAINTENANCE COST OF RIGID PAVEMENT

The average yearly maintenance cost of rigid pavement will be about Rs 10000per km for a single lane rural road to cover filling of sealing compound in the joints requires of concrete spalling etc

LIFE CYCLE COST ANALYSIS OF RIGID PAVEMENT

Period of analysis has been considered as 20 years being the design life of concrete pavement in rural area the discount rate of 10 has been taken inflation rate of 5 has been considered for future rise in prices of materials

CEMENT CONCRETE PAVEMENT VS BITUMINOUSPAVEMENT- A COST ANALYSIS

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

CONCLUSION

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation

India economical growth plan of over 6 per annum for the next 20 years will to a great extent depend on an efficient road infrastructure not only national highways but other roads too including link roads for rural connectivity which can provide fast movement of goods and people with safety and economical cost to the user government of India has drawn up Pradhn Mantri gram Sarak Yojana(PMGSY) for implementation of rural connectivity it is estimated that in the next 7 years road works under PMGSY worth Rs 120000 crores are to be constructed

Since road pavements are an important part of these projects costing about 50 of the investment a careful evaluation of the alternatives is necessary to make the right choice on a rational basis which may be comparatively more beneficial to the nation