A Summer Training Report

OnCONSTRUCTION OF CEMENT CONCRETE PAVEMENT

At

UTTAR PRADESH PUBLIC WORKS DEPARTMENTCONSTRUCTION DIVISION-1, GORAKHPUR (U.P)

SUBMITTED BY:- AWINASH TIWARI BRANCH: CE, 4th Year ROLL NO. 1302900036

SUBMITTED TO:- DEPARTMENT OF CIVIL ENGINEERING K.I.E.T ,GHAZIABAD

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ACKNOWLEDGEMENT

I express my satisfaction on the completion of this summer training program and project report submission as a part of the curriculum for the degree of Bachelor of Technology, Civil Engineering. I express my deepest gratitude to my supervisor and mentor Mr. SHIV KUMAR SINGH SIR and MR. ARWIND KR. NAMDEV SIR for his kind guidance during the entire period of training. His consistent support and advices has helped me to complete this research project successfully. Also I thank all the members of PUBLIC WORKS DEPARTMENT, CONSTRUCTION DIVISION-1, GORAKHPUR, U.P. for their kind support. They have always been a source of inspiration to me.

DATE: - 05/08/2016

AWINASH TIWARI

College: K.I.E.T GZB

Branch: CE, 4th Year

Roll No.130200036

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TABLE OF CONTENTS

S. NO. CONTENT PAGE NO. 1 PUBLIC WORKS DEPARTMENT: AN OVERVIEW 5

2 INTRODUCTION 6

3 WHAT IS ROAD OR PAVEMENT? 8

4 TYPES OF PAVEMENTS 9

5 TYPES OF CONCRETE PAVEMENT 11

6 MINERALS USED 12

7 CEMENT

8 SAND

9 AGGREGATE

10 PROPORTIONING 16

11 PROCEDURE TO CONSTRUCT PAVEMENT 17

12 PREPARATION OF THE SUB- GRADE OR BASE COARSE

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13 MIXING AND TRANSPORTATION OF CONCRETE 19

14 PLACING OF CONCRETE 21

15 SLIPFORM CONCRETE PAVING 22

16 EXECUTION OF JOINTS 25

17 CURING 28

18 PROTECTION OF THE CONCRETE PAVEMENT 29

19 SPECIAL MEASURES 31

20 OPENING TO TRAFFIC 33

21 COST ANALYSIS OF RIGID PAVEMENT 34

22 CONCLUSION

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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, electrical and 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 country's construction industry under the close supervision of the Ministry of Housing and 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.

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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 roads.

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Point of view geographic and population of the state is the nation's 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 SadakYojana 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.

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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 – 30 years.

Road pavements deteriorate over time due to- The impact of traffic, particularly heavy vehicles. Environmental factors such as weather, pollution.

PURPOSE Many 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.

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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.

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Hence it will be in India's 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 – wide ranging temperatures, 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. R&D efforts should be initiated in this area.

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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 4.5 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, i.e. less than 0.3 mm.

Reinforced pavement slabs

Reinforced 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 limited.

Steel fibre concrete The 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.

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MINERALS USEDConcrete 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 concrete.

There are mainly three materials used primarily-

1.CEMENT

Cement is abinder, 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 describemasonryresembling modernconcretethat was made from crushed rock with burntlimeas binder. Thevolcanic ashand pulverizedbrickadditives 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 (e.g.,Portland cement) harden because ofhydration, a chemical reaction between theanhydrouscement 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 ofmortarin masonry, and ofconcrete, a combination of cement and an aggregateto form a strong building material.

• TYPES OF CEMENT:- a. Portland cement

Portland cement is by far the most common type of cement in general use around the world. This cement is made by heatinglimestone(calcium carbonate) with small quantities of other materials (such asclay) to 1450 °C in akiln, in a process known ascalcinations, whereby a molecule ofcarbon dioxideis liberated from the calcium carbonate to formcalcium oxide, or quicklime, which is then

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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 ofgypsuminto 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 ofconcrete,mortarand most non-specialtygrout. The most common use for Portland cement is in the production of concrete. Concrete is a composite material consisting ofaggregate(gravelandsand), cement, andwater. 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.

b. 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.

c. Portland pozzolana cement Its includes fly ash cement, since fly ash is a pozzolana , but also includes cements made from other natural or artificial pozzolans. In countries wherevolcanic ashesare available.

d. Portland silica fume cementAddition ofsilica fumecan yield exceptionally high strengths, and cements containing 5– 20% silica fume are occasionally produced. However, silica fume is more usually added to Portland cement at the concrete mixer

2.SAND

Sand is a naturally occurringgranularmaterialcomposed 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 nontropicalcoastalsettings issilica(silicon dioxide, or SiO2), usually in the form ofquartz.

The second most common type of sand iscalcium carbonate, for examplearagonite, which has mostly been created, over the past half billion

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years, by various forms of life, likecoralandshellfish. It is, for example, the primary form of sand apparent in areas where reefs have dominated the ecosystem for millions of years like theCaribbean.

3.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 or crushed stone with most particles passing through a 3/8-inch (9.5-mm) sieve. Coarse aggregates are any particles greater than 0.19 inch (4.75 mm), but generally range between 3/8 and 1.5 inches (9.5 mm to 37.5 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 concreteis 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 quality.

Once processed, the aggregates are handled and stored in a way that minimizes segregation and degradation and prevents contamination. Aggregates strongly influence concrete's 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:

• grading • durability • particle shape and surface texture • abrasion and skid resistance • unit weights and voids • absorption and surface moisture

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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.

A. 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 501.3.6.3 of the Standard Specifications for Highway and Structure Construction, current edition.

B. 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 501.3.6.4 of the Standard Specifications for Highway and Structure Construction, current edition.

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PROPORTIONING: 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 2.65. 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 2.65 .

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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 investigation.

• after survey , a team of experienced engineers and architecture prepare detailed plan of work with the help of various soft ware's.

• after that a engineer prepares detailed estimate of proposed work and also prepares a estimate regarding equipments required and labours requirements.

• now excavation is done with the help of automatic machines and then a equipment is used to cut nearby trees and root removal process.

• and after these construction of soil sub grade , base coarse and then construction of concrete slab is done.

PREPARATION OF THE SUB- GRADE OR BASE COARSE

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 structure.

For 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 (e.g. 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 foundation:

• Drainage of all surface water; • Good compaction of the sub grade; • Filling and compaction of any ruts caused by construction traffic;

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• It 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 e.g. with a grain size 0/20;

• Provide 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.

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MIXING AND TRANSPORT OF CONCRETE

• CONCRETE 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 the loaders 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 (i.e. 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 (e.g. 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.

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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 roadwork's 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.

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SLIP FORM CONCRETE PAVING

• PREPARATION OF THE TRACK RUNWAY The quality of the runway for the tracks of the paving equipment [10] 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 deformations;

• good skid resistance to prevent the tracks from slipping, especially when paving on a slope;

• good evenness to avoid that the self-levelling systems have to compensate for excessive differences in height. The track runway is a determining factor for the steering 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 on embankments);

• 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 unevenness's. This implies a sufficient capacity of the concrete mixing plant and of the means of transportation of the concrete.

The concrete is discharged:

• either 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 mix;

• or in the bin of a side feeder, for example if transport by dump trucks on the foundation is impossible because of the presence of dowel chairs or reinforcement steel;

• or in a supply container, from which the concrete is scooped with a crane.

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It 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 placer/spreader machine that operates in front of the paver or, by the slip form paver itself (side feeder, spreading augers, wagon,…). The use of a placer/spreader, allows the slip form paver to proceed more steadily. The distance between the placer/spreader 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 0.75 and 1 m/min. 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 smoothness.

Some 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 unevenness's 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.

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• 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 circumstances,

• a regular supply of concrete and a uniform spreading in front of the paver,

• correct 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, etc.,

• steady progress of the paver, without interruptions and with a speed compatible with the consistency of the concrete and the working circumstances,

use of specific tools or equipment to eliminate small bumps after the paving machines: correction beam, super smoother, etc.

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• 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, i.e. 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 (“wild”) 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 2.5 cm deep. Every saw cut that has not instigated a crack within 24 hours is deepened up to 1/3 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 1/3 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

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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 surface.

After 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 JOINTSExpansion 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 placed;

• the 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 “concrete arch” is made at the top of the joint;

• expansion 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 JOINTSConstruction 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.

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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 4.5m. 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 1/3 of the thickness of the slab.

2. LONGITUDINAL CONSTRUCTION JOINTS These are joints between two adjacent concrete lanes that are executed successively.

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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 works • Covering with hessian & gunny bags • Sprinkling of water • By ponding • Membrane curing

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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. E.g. at an ambient temperature of 20°C, a relative humidity of 60 %, a temperature of the concrete of 25°C and a wind speed of 25 km/h, 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 [43]. 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 of the skinof 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 g/m2 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.

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3.PROTECTION AGAINST FROST When concrete is placed in cold weather (see also § 8.4.1) 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 ºC 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.

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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 1.5 m above ground under thermometer shelter does not exceed 25°c.

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

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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 %.

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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, i.e. between 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.

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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 COST The maintenance cost includes the maintenance of pavement during the design life of pavement to keep the pavement at the specified service level.

In 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.

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RIGID PAVEMENT DESIGN AND COSTOF CONSTRUCTION PER KILOMETERS

The 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: SP:62-2004):

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.

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CEMENT CONCRETE PAVEMENT VS BITUMINOUS PAVEMENT- A COST ANALYSIS

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CONCLUSION

India„iseconomical 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 PradhnMantri gram SarakYojana(PMGSY) for implementation of rural connectivity. it is estimated that in the next 7 years, road works under PMGSY worth Rs. 1,20,000 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.

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