anish dhillon report indiabulls
DESCRIPTION
Report on Building ConstructionTRANSCRIPT
An
INDUSTRIAL TRAINING REPORT
ON
“ Mega Mall Jodhpur ”
At INDIABULLS, Real State
Submitted in partial fulfillment of Bachelors of Technology in Civil Engineering at
IEC UNIVERSITY, BADDI(H.P).
2015-2016
Submitted to- Submitted by-
Mrs. Suman Thakur ANISH DHILLON
2012010211
DEPARTMENT OF CIVIL ENGINEERING
FACULTY OF ENGINEERING AND TECHNOLOGY
BADDI, (H.P)
1
ACKNOWLEDGEMENT
It is a matter of great pleasure and privilege for us to present this report of 6 weeks on basis of
practical knowledge gained by us during industrial training at INDIABULLS Real Estate
Jodhpur during session 2015-16.
I would like to express my deepest gratitude to Mr. C. L. Meenafor giving me the opportunity to undertake my summer training in their working area.
I feel indebted to express my heartiest thanks and deep sense of gratitude to Mr. Laxmi Narayan
and Mr. Virendra Singh Sisodiya for their valuable guidance and time.They were always there
with their competent guidance and valuable suggestions throughout the pursuance of this
training.
I would also like to place an appreciation for Mr. Hari Singh Rathore and Mr. Ramnivas Yadavfor giving me some guidance regarding safety involved in construction of any project.
Anish Dhillon
2012010211
2
PREFACE
Engineering students gain theoretical knowledge from their books only but theoretical
knowledge is not sufficient for absolute mastery in any field.
Theoretical knowledge given in our books is not of much use without knowing its practical
implementation it has been experienced that theoretical knowledge is volatile in nature however
practical knowledge makes solid foundation of our mind.
I took my training in INDIABULLS real estate Jodhpur from 30 June 2015 to 15 august 2015
and succeeding chapter give about what I have learnt in this prestigious organization.
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TABLE OF CONTENT
S.No. TOPIC PAGE
Certificate
Acknowledgement
Preface
Chapter no. Page No
Chapter 1 Introduction 6 1.1 About construction site 7
1.2 Site Layout 10
1.3 Services and security 15
Chapter 2 Literature review 162.1 Construction material 16
2.1.1Cement 16
2.1.2 Aggregate 19
2.1.3 Bricks & form blocks 22
2.1.4 Water 24
2.1.5 Steel bars 24
2.1.6 Shuttering 25
2.2 Construction Process 26
2.2.1 Sequence of Structure Work 26
1) Site Clearance
2)Demarcation of Site 3)Surveying and layout
27
27
4
4)Excavation
5)Laying of PCC or foundation
6)Bar Binding and placement of foundation steel
7)Shuttering and Scaffolding
8)Concreting
9)De shuttering
10)Electrical and Plumbing installations
11)Masonary and Brickwork
12) Curing
13)Placing of lintels
14) Leakage and Water Proofing
15)Plastering
16)Flooring and tiling work
27
28
33
37
47
50
61
63
63
64
66
66
68
69
2.3 Safety Equipments 70
Chapter 3 Conclusion 71
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1. INTRODUCTIONThe building is defined as any structure what so everpurpose and of whatsoever materials
constructed and everpart thereof whether used as human habitation or not. For this practical
training i reported at INDIABULLS real estate jodhpurat Construction ofINDIABULLS MEGA
MALL at new pali road, NH65 at Vijay raje nagar, Jodhpur .The site engineer Mr. Laxmi
Narayan sir and Mr. Virendra singh sisodiya Sir meets me at the site and givesme brief
introduction of this project as under.
Company Profile:
Indiabulls Real Estate is one of India’s largest and fastest growing real estate companies, building high-end residences, mega townships, commercial and office complexes, state-of-the-art SEZs and retail spaces. Today the company has an area of over 58 million sq. ft. under development across 31 projects in the country. The company also has an additional land bank of 340 acres and about 2500 acres for SEZ development.
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1.1 ABOUT CONSTRUCTION SITE
The project on which I take practical training this project is a construction of a commercial and
business (mall). This project has the following features:
Name : INDIABULLS Mega Mall
Type: Commercial
Location: NH65, new pali road , vijay raje nagar , Jodhpur .
Client: INDIABULLS real estate, Gurgaon .
Architect: ADA Anupam De Associates
Consultant: JW Consultants
Construction Company: S&S technocrats pvt. Ltd. & Karni Kripa Const. Pvt Ltd.
PT Work : UTRACON Pvt. Ltd.
Land Size : 200,000 Sq Ft.
Cost of the Project: 350 to 400 crore rupees
No. of stories: 11 level, (including 2 basements , lower and upper
groundfloor)
Height of Building: 30 meter (From ground level to terrace level)
The building is fully air-conditioned. It has fire detection system and fire fighting system and
escape way in the cariouscondition. This building is earth quakebuilding (mega mall). It has 13
lifts. This building have fully power backup.
Project Highlights:
1. Road facing shops and retail spaces starting from 300 sq. ft.2. Multiplex, Food Courts, Entertainment Zones, Office Spaces.3. Sprawling across 6,00,000 sq. ft.4. Lower maintenance costs.
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Location Highlights:
1. Located in Vijaya Raje Nagar on Pali Road.2. Opposite National Zoological Survey Office.3. 8 kms from the Airport, Railway Station and Bus Terminal.4. Adjacent to the proposed High Court.
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MAPS OF SITE -
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1.2 SITE LAYOUTS –
Lower ground floor plan
10
Ground floor plan
1st floor plan
11
2nd floor plan
3rd floor plan
12
4th floor plan
5th floor plan
13
6th floor plan
7th floor plan
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1.3 SERVICES AND SECURITY
Services are:
Water
Electricity
Storm water
Sewerage
Gas
Council requires that a temporary electrical sub-station and toilet facilities be established on-site
before construction commences.If there are no or insufficient services on site, or they need
extending, permission from council and relevant authorities will be required.
Security
A hoarding (site fencing) will also need to be erected and is to remain for the entire construction
period.
The builder may have to use a combination of swelling, hay bales and sedimentation fencing on
a sloping block to stop earth falling onto the road or into drains and waterways.
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2.LITRATURE REVIEW
2.1 CONSTRUCTION MATERIAL
2.1.1 Cement :-The cement often called the magic power is a fine ground material consisting of compound of
lime, silica alumina and iron. When mixed with water it forms a paste which hardened and bind
the aggregates (sand, gravel, crushed rock, etc) together to form a durable mass called the
Concrete. Cement is the binder that holds concrete and mortars together. This is why it plays the
most critical role in giving strength and durability to your building. Cement uses for domestic
building such as home are basically of three types.
1)Portland Slag Cement
2)Portland Pozzolana Cement
3)Ordinary Portland Cement
Cement is a hygroscopic material meaning that it absorbs moisture In presence of moisture it
undergoes chemical reaction termed as hydration. Therefore cement remains in good condition
as long as it does not come in contact with moisture. If cement is more than three months old
then it should be tested for its strength before being taken into use.
The Bureau of Indian Standards (BIS) has classified OPC in three different grades The
classification is mainly based on the compressive strength of cement-sand mortar cubes of face
area 50 cm2 composed of 1 part of cement to 3 parts of standard sand by weight with a water-
cement ratio arrived at by a specified procedure. The grades are
(i) 33 grade
(ii) 43 grade
(iii) 53 grade
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The grade number indicates the minimum compressive strength of cement sand mortar in
N/mm2 at 28 days, as tested by above mentioned procedure.
Portland Pozzolana Cement (PPC) is obtained by either intergrinding a pozzolanic material with
clinker and gypsum, or by blending ground pozzolana with Portland cement. Nowadays good
quality fly ash is available from Thermal Power Plants, which are processed and used in
manufacturing of PPC.
Advantages of using Portland pozzolana cement over OPC
Pozzolana combines with lime and alkali in cement when water is added and forms compounds
which contribute to strength, impermeability and sulphate resistance. It also contributes to
workability, reduced bleeding and controls destructive expansion from alkali-aggregate reaction.
It reduces heat of hydration thereby controlling temperature differentials, which causes thermal
strain and resultant cracking n mass concrete structures like dams. The colour of PPC comes
from the colour of the pozzolanic material used. PPC containing fly ash as a pozzolana will
invariably be slightly different colour than the OPC. One thing should be kept in mind that is the
quality of cement depends upon the raw materials used and the quality control measures adopted
during its manufacture, and not on the shade of the cement. The cement gets its colour from the
nature and colour of raw materials used, which will be different from factory to factory, and may
even differ in the different batches of cement produced in a factory. Further, the colour of the
finished concrete is affected also by the colour of the aggregates, and to a lesser extent by the
colour of the cement. Preference for any cement on the basis of colour alone is technically
misplaced.
Settling Of Cement
When water is mixed with cement, the paste so formed remains pliable and plastic for a short
time. During this period it is possible to disturb the paste and remit it without any deleterious
effects. As the reaction between water and cement continues, the paste loses its plasticity. This
early period in the hardening of cement is referred to as ‘setting’ of cement.
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Initial and final setting time of cement
Initial set is when the cement paste loses its plasticity and stiffens considerably. Final set is the
point when the paste hardens and can sustain some minor load. Both are arbitrary points and
these are determined by Vicat needle penetration resistance
Slow or fast setting normally depends on the nature of cement. It could also be due to extraneous
factors not related to the cement. The ambient conditions play an important role. In hot weather,
the setting is faster, in cold weather, setting is delayed Some types of salts, chemicals, clay, etc if
inadvertently get mixed with the sand, aggregate and water could accelerate or delay the setting
of concrete.
Storage of Cement
It needs extra care or else can lead to loss not only in terms of financial loss but also in terms of
loss in the quality. Following are the don’t that should be followed -
(i) Do not store bags in a building or a go down in which the walls, roof and floor are not
completely weatherproof.
(ii) Do not store bags in a new warehouse until the interior has thoroughly dried out.
(iii) Do not be content with badly fitting windows and doors, make sure they fit properly and
ensure that they are kept shut.
(iv) Do not stack bags against the wall. Similarly, don’t pile them on the floor unless it is a dry
concrete floor. If not, bags should be stacked on wooden planks or sleepers.
(v) Do not forget to pile the bags close together
(vi) Do not pile more than 15 bags high and arrange the bags in a header-and-stretcher fashion.
(vii) Do not disturb the stored cement until it is to be taken out for use.
(viii) Do not take out bags from one tier only. Step back two or three tiers.
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(ix) Do not keep dead storage. The principle of first-in first-out should be followed in removing
bags.
(x) Do not stack bags on the ground for temporary storage at work site. Pile them on a raised, dry
platform and cover with tarpaulin or polythene sheet.
Cement Storage
2.1.2 Aggregate :-‘Aggregates’ is a general term applied to those inert (that chemically inactive) Material, which
when bounded together by cement, form concrete. Most aggregates used in this country naturally
occurring aggregates such as sand, crushed rock and grawel.
Aggregates for concrete are divided into three categories
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Coarse Aggregate
Coarse aggregate for the works should be river gravel or crushed stone .It should be hard, strong,
dense, durable, clean, and free from clay or loamy admixtures or quarry refuse or vegetable
matter. The pieces of aggregates should be cubical, or rounded shaped and should have granular
or crystalline or smooth (but not glossy) non-powdery surfaces. Aggregates should be properly
screened and if necessary washed clean before use.
Coarse aggregates containing flat, elongated or flaky pieces or mica should be rejected. The
grading of coarse aggregates should be as per specifications of IS-383.
After 24-hrs immersion in water, a previously dried sample of the coarse aggregate should not gain in
weight more than 5%.
Aggregates should be stored in such a way as to prevent segregation of sizes and avoid
contamination with fines.
Depending upon the coarse
aggregate color, there quality can
be determined as:
Black = very good quality
Blue = good
Whitish =bad quality
Coarse Aggregate
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Fine Aggregate
Aggregate which is passed through 4.75 IS Sieve is termed as fine aggregate. Fine aggregate is
added to concrete to assist workability and to bring uniformity in mixture. Usually, the natural
river sand is used as fine aggregate. Important thing to be considered is that fine aggregates
should be free from coagulated lumps.
Sand
These are cohesion less aggregates of either, rounded sub rounded, angular, sub angular or flat
fragments of more or less unaltered rock of minerals consisting of 90% of particles of size
greater than 0.06 mm and less than 2 mm. Alternatively, these are coarse grained cohesion less
particles of silica derived from the disintegration of rock. These are of three types:
Coarse sand:It is one which contains 90% of particles of size greater than 0.6 mm and less
than 2 mm.
Medium sand:It is one, which contains 90% of particles of particles size greater than 0.2 mm
and less than 0.6 mm.
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Fine sand:It is one, which contains 90% of particles of size greater than 0.06 mm and less than
0.2 mm.
2.1.3 Masonary (bricks & form blocks):-
In the construction of this project, masonry in whole complex is done with fly ash blocks. These blocks are very light in weight, so masonry will be raised a lot easily and the labors will need to put less effort. They are also Sound-proof.
Mortar of cement:sand ratio 1:4 is used in construction of masonry.
Comparison of brick and fly ash block:
Let us take a block of dimensions 200x225x600 mm3.
Hence, volume of block = 200x225x600 = 27000000 mm3
Brick dimensions = 200x100x100
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So, volume of brick = 2000000 mm3
No. of bricks in place of 1 block = 27000000/2000000 = 13.5 = 14 bricks.
Cost of 1 brick = Rs. 5
Total cost = 5x14 = Rs. 70 with more labor requirement, more mortar use, more damage, etc.
And cost of 1 block = under Rs. 100
Therefore, use of fly ash block instead of brick is profitable.
FIG: FLY ASH BLOCK
Reinforcement of diameter 6 mm is provided between joints of masonry after every 3rd layer. It is used to provide support and strength to masonry blocks.
Types of Bond
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2.1.4 WATER :-
The strength and durability of concrete depends also on the amount of water mixed with it. Too
much or too little water can adversely affect the strength of concrete. After concrete is cast, water
is used to cure it so that the temperature is controlled and concrete matures slowly. It is very
important to use clean, potable water in quality concrete production. Brackish or salty water must
never be used. Contaminated water will produce concrete.
Mortars with lower durability, erratic set characteristics and inconsistent color.
2.1.5 STEEL BARS :-
Mild steel bars conforming to IS: 432 (Part I) and Cold-worked steel high strength deformed bars
conforming to IS: 1786 (grade Fe 415 and grade Fe 500, where 415 and 500 indicate yield
stresses 415 N/mm2 and 500 N/mm2 respectively) are commonly used. Grade Fe 415 is being
used most commonly nowadays. This has limited the use of plain mild steel bars because of
higher yield stress and bond strength resulting in saving of steel quantity. Some companies have
brought thermo mechanically treated (TMT) and corrosion resistant steel (CRS) bars with added
features.
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Bars range in diameter from 6 to 50 mm. Cold-worked steel high strength deformed bars start
from 8 mm diameter. For general house constructions, bars of diameter 6 to 20 mm are used.
In our site 8-32mm bars are used i.e. 8,10,12,16,20,25,32 mm bars are used.
It is wise to buy good brands the names of which are marked on the steel. During construction make sure that steel reinforcement is provided exactly as the engineering design specification.
2.1.6
SHUTTERING :-
A fresh concrete is in a plastic state, when it is placed
for construction purpose ,so it become necessary to
provide some temporary structure to confine and
support the concrete ,till it gains sufficient strength for
self supporting this temporary structure known as
shuttering.The term ‘SHUTTERING’ or
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Reinforcement Steel
‘FORMWORK’ includes all forms, moulds, sheeting, shuttering planks, walrus, poles, posts,
standards, leasers, V-Heads, struts, and structure, ties, prights, walling steel rods, bolts, wedges,
and all other temporary supports to the concrete during the process of sheeting.
2.2 Construction Process
2.2.1 Sequence of Structure Work:
1)Site Clearance
2)Demarcation of Site
3)Surveying and layout
5)Excavation
6)Laying of PCC or foundation
7)Bar Binding and placement of foundation steel
8)Shuttering and Scaffolding
9)Concreting
10)Deshuttering
11)Electrical and Plumbing installations
12)Masonary and Brickwork
13) Curing
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Shuttering
14)placing of lintels
15) Leakage and Water Proofing
16)Plastering
17)Flooring and tiling work
18)Final Completion and handing over the project.
1) Site clearance:-
The very first step is site clearance which involves removal of grass and vegetation along with any other objections which might be there in the site location. This process is also known as ‘Grubbing’.
2) Demacration of site:-
Before demolition can begin:
All services such as power, water, gas etc need to be disconnected.
Storm water and sewer drains will need to be sealed as well.
Adjoining properties may need to be protected.
The site must be fenced or suitably barricaded to prevent public access during the
demolition process.
The whole area over which construction is to be done is marked so as to identify the construction zone. In our project a plot of 2 lakh sq. ft. was chosen and respective marking was done.
New legislation requires that where possible materials from demolition must be retained for
reuse, resale or recycling. Recycling commitments will need to be outlined to council in the DA
stage.
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Where asbestos or materials containing asbestos are involved in the demolition works,
compliance with Work Cover or Work Safe legislation must be maintained at all times.
3) Surveying and Layout:-
A surveyor marks reference points and markers that will guide the construction of new structures such as roads or buildings. These markers are usually staked out according to a suitable coordinate system selected for the project. A surveyor marks reference points and markers that will guide the construction of new structures such as roads or buildings. These markers are usually staked out according to a suitable coordinate system selected for the project.
4) Excavation:-
Excavation was carried out initially for investigating the soil and then laying the PCC and masonry for foundation. If required, steel placement is also done for foundation.
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FIELD INVESTIGATION :
The overall purposes of this study are to investigate the stratigraphy (arrangement and succession of strata) at the site and to develop geotechnical recommendations for foundation design and construction. To accomplish these purposes the study was conducted in the following phases:
A) Drilling 8 boreholes in the main complex area through soil and rock/refusal strata to 20 m depth and 4 boreholes to 30 m depth in order to determine site stratigraphy and to collect disturbed and undisturbed soil/rock samples for laboratory testing;
a) Drilling 4 boreholes in the offset area to 5 m depth through soil and rock/refusal strata in order to determine site stratigraphy and to collect disturbed and undisturbed soil/rock samples for laboratory testing;
b) Testing selected soil/rock samples in the laboratory to determine pertinent index and engineering properties of the soil/rock;
c) Analyzing all field and laboratory data in order to develop engineering recommendations for foundation design and construction.
SOIL BORINGS:
The boreholes were progressed using a mechanized shell and auger to the specified depth or refusal, whichever is encountered earlier. The borehole diameter was 150 mm. Where caving of borehole occurred, 150 mm diameter casing was used to keep the borehole stable. The work was in general accordance with IS: 1892-1979.
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Standard Penetration Test (SPT) were conducted in the boreholes at 1.5 m depth intervals. The test was performed by connecting a split spoon sampler to ‘A’ rods and driving it by 45 cm using a 63.5 kg hammer falling freely from a height of 75 cm. The tests were conducted in accordance with IS: 2131-1981. The SPT values or the ‘N’ values are presented on the soil profile for each borehole.
Disturbed samples were collected from the split spoon after conducting SPT. The samples were preserved in transparent polythene bags.
Undisturbed samples were collected by attaching 75 mm diameter thin walled ‘Shelby’ tubes and driving the sampler using a 63.5 kg hammer in accordance with IS: 2132-1986. The tubes were sealed with wax at both ends.
All samples were transported in the NABL accredited Delhi Laboratory for further examination and testing.
ROCK DRILLING:
Rotary drilling through the rock was performed using heavy-duty skid mounted Joy Voltas 12B diamond coring rotary drill machine. The drill machine has a hydraulic feed and is driven by a bevel gear system run by a 28 HP Perkin engine.
The percent recovery and Rock Quality Designation (RQD) was measured for each core run. The percent recovery is defined as the percent ratio of the cumulative length of core sample recovered to the total length of the core run.
The RQD is defined as the ratio of the cumulative length of core pieces 10 cm or longer to the total length of the core run. High-quality rock has an RQD of more than 75%, low quality of less than 50%. It is a rough measure of degree of jointing or fracture in rock mass.
From the RQD index the rock mass can be classified as follows:
RQD Rock mass quality<25% very poor25-50% Poor50-75% Fair75-90% Good
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90-100% Excellent
The Rock Mass Rating (RMR), an engineering parameter assists in assessing the rock quality and behavior is also presented on the individual rock profiles.
Details of samples collected are presented on the rock profiles together with recovery, RQD and RMR values at various depths.
GROUND WATER:
Ground water level was measured in the boreholes 24 hours after drilling and sampling was completed. The measured water levels are recorded on the individual soil profiles.
PLAN FOR THE SYSTEM OF BOREHOLES :
It is shown in the figure below-
SOIL PROFILE FOR BOREHOLE 1:
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Laboratory Tests
The laboratory testing has been carried out in NABL accredited laboratory. The quality procedures in our laboratory conform to ISO/IEC-17025-2005.
The laboratory testing programme was aimed at verifying that the field classifications and developing parameters for engineering analysis. All testing was performed in accordance with the current applicable IS specifications. The following tests were conducted on selected soil/rock samples recovered from the borehole:
On Soil:
Laboratory Test IS Code ReferredGrain size analysis IS : 2720 (Part-4)-1985Liquid Limit and Plastic Limit IS : 2720 (Part-5)-1985Specific Gravity IS : 2720 Part-III-1980Consolidated drained direct shear test IS : 2720 Part-XIII-1986Chemical analysis of soil to determine pH value, sulphates and chlorides*
IS : 2720 (Part-27)-1977IS : 2720 (Part-26)-1973
Chemical analysis of ground water to determine, sulphates, chlorides and pH value*
IS : 2720 (Part-11)-1983IS : 2720 (Part-24)-1986IS : 2720 (Part-32)-1988
*outside NABL Scope
General Site Conditions:
GENERAL:
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The project site covers an area of 5.77 acres ( 2.51 lakh sq. ft.). The site is fairly level, with the ground surface elevations ranging from RL 98.2 m to RL 101 m, based on contour plans.
GEOLOGY:
The change in climate from arid to semi-arid is marked by the formation of widespread calcrete that incorporated clastic angular fragments of ferricate at Jaisalmer, Jodhpur-Barmer and Jayal-Chhajoli areas. The deposition of boulders and gravels of quartzite and polymictic quartzite conglomerate, consisting of immature clasts of granites, gneisses, schists, etc., suggests rapid sedimentation in a neo-tectonically disturbed region.
SITE STRATIGRAPHY:
The deposits at site may be divided into 2 generalized strata as described below:
Stratum-I : Overburden Soils
Stratum-II : Rock (Calcretized Conglomerate)
The soils at the site consist of calcareous silty sand that extends from the ground surface to the top of the underlying rock to about 9.0~15.0 m depth. At BH-16 calcareous silty sand is met to the final explored depth of 5.20~5.45 m.
SPT values in the overburden range from 32 to 50 to about 2.0 m depth. Below this, SPT values generally exceed 100 to top of the underlying rock formation.
The underlying rock formation classifies as calcretized gritty conglomerate. The rock is very severely weathered and disintegrated into calcareous coarse sand and gravel. In general, the borehole through this deposit was progressed by chiseling. However, rotary drilling was carried out at BH-6 and 7. The core recoveries at these borehole locations range from 5 to 8%. The RQD value is nil (zero percent). The RMR value of the rock is about 15.
GROUNDWATER:
Based on our measurements in the completed boreholes, groundwater was met between 10.2 to 12.3 m depths below ground level (RL 86.9~88.4 m) at the time of our field investigation (January, 2008).
5) Laying of PCC or Foundations :- Foundation Analysis and Recommendations
GENERAL:
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A suitable foundation for any structure should have an adequate factor of safety against exceeding the bearing capacity of the supporting soils. Also the vertical movements due to compression of the soils should be within tolerable limits for the structure. We consider that foundation designed in accordance with the recommendations given herein will satisfy these criteria.
FOUNDATION TYPE AND DEPTH:
(a) MAIN MALL COMPLEX AREA :
It is proposed that the proposed mall complex shall have a double basement with upper floors. The foundation level is likely to be at about 9.0~10.0 m depth below the finished ground level in the main mall complex area.
Open or raft foundations bearing on soils/refusal strata at a depth of 9.0~10.0 m below existing ground surface is a suitable foundation scheme. Foundations at basement level may consist of isolated column foundations with an interconnected beam or T-beam and slab (designed as strip footing). Raft foundations are also a suitable foundation system.
All foundations should be seated either on the soil or on the weathered rock formation, not partly on soil and partly on rock. We recommend as follows:
1.Foundations for any individual structure may bear either on soil or on weathered rock, but not on both. In case foundation is bearing on rock, it should be seated at least 0.5m into the weathered rock.
2.Where excavations to the desired founding level exposes weathered rock at most location, the soil encountered at foundation level should be over-excavated to the top of the rock level. The excavated soil should be replaced by a lean concrete to the desired founding level.
3.Where excavation to the desired foundation level for a particular building exposes soil at most locations, the rock encountered at foundation level should be over-excavated by 0.3 m and replaced by a compacted sand cushion.
(b) OFFSET AREA:
Open foundation may be provided for minor facilities in the offset such as boundary wall, security gate, small room etc in the offset area. We recommend a minimum foundation embedment depth of 1.2 m for lightly loaded 1-2 storeyed buildings. For structures taller than 1-2 storeys, the foundation embeded should be atleast 1.5 m . Recommendations are presented herein for foundation at 1.2 m to 3.5 m below the finished ground level.
OPEN FOUNDATIONS:
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Bearing capacity for analysis for individual spread foundations, isolated foundations and strip footing have been done in general accordance with IS: 6403-1981, Soil parameters used for foundation analysis are s follows:
Foundation Embedment Depth, m
Foundation Bearing Material
C, T/m2 ᶲ Nq Ny Remarks
1.2-1.5 Sand 0 30 18.40 22.40 General shear Failure
3.0 Sand 0 30 18.40 22.40 General Shear Failure
9~10 Sand/calcretized conglomerate
0 33 18.40 22.40 General Shear Failure
Where:
C = cohesion intercept
ᶲ= angle of internal friction
Y = effective unit weight of soil
Nc, Nq, Ny=Bearing capacity factors which are a function of ᶲ
Settlement analysis has been performed based on the SPT values in accordance with Clouse 9.1.4 of IS 8009 (Part 1)-1976. For the purpose of analysis, the weathered disintegrated rock has also been treated as a dense sand.
RECOMMENDED NET ALLOWABLE BEARING PRESSURE:
Following values recommended for net allowing bearing pressure for open foundations in the offset and main mall complex areas at different depths:
FoundationEmbedment Depth, m
LikelyFoundationBearing level
RecommendedNet Allowable BearingPressure, T/m2
Recommended Gross Allowable BearingPressure, T/m2
ProposedModulus of Subgrade Reaction Kg/cm3
Offset Area 1.2 Sand 10.0 - 0.8 1.5 Sand 12.0 - 1.0 3.0 Sand 15.0 - 1.2Main Mall Complex Area 9.0 Sand 25.0 40.0 2.0 10.0 Sand 28.0 45.0 2.5
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10.0~11.0 Sand 32 49.0 2.8
It should be ensured that all foundations bear on uniform bearing strata. The above values include a bearing capacity safety factor of 2.5. Total settlement of bearing on soil designed for the above recommended net bearing pressures is expected to be about 40mm. For foundations on the weathered conglomerate, the total settlement may be about 15-25mm.
BASEMENT DESIGN:
The basement should be water-proof adequately and designed to resist lateral earth pressure as well as hydrostatic pressure. For the purpose of design, the groundwater should be considered to rise to about 5m depth below EGL. The basement should be designed to resist the consequent uplift force with an adequate safety factor.
The backfill material behind the basement retaining walls shall exert lateral earth pressure on the wall. The basement wall should also be designed to resist hydrostatic thrust.
Depth, m Ka Kb K0
From To 0.0 3.0 0.33 3.00 0.50 3.0 6.0 0.32 3.12 0.48 6.0 11.0 0.29 3.39 0.46Where:
Ka= co-efficient of active earth pressure
Kp= co-efficient of passive earth pressure
K0 = co-efficient of earth pressure at rest
A suitable safety factor should be applied on the passive earth pressure in the design of the wall.
LIQUEFACTION POTENTIAL:
As per IS:1883 (Part-1):2002, Table -1 liquefaction is likely in fine sands below water table with SPT values less than 15 to about 5.0 m depth and less than or equal to 25 below10.0 m depth. For values of depths between 5 m to 10 m, linear interpolation is recommended.
The soils at the site classify primarily as calcretized silty sand from the ground surface to the top of the underlying rock at about 9.0~15.0 m depth. SPT values in the overburden range from 32 to 50 to about 2.0 m depth. Below this, SPT values generally exceed 100. Groundwater was met at 10.2 to 12.3 m depth.
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The site falls in earthquake Zone-II as per IS: 1893-2002. The design should be done considering the earthquake parameters for Zone-II.
Foundation construction consideration
EXCAVATIONS:
Excavation through soil to about 3 to 4 m depth may be cut using side slopes of 1-vertical on 0.6 to 1.0 horizontal. Deeper excavation may be cut using side slopes of 1-vertical on 0.5 to 0.8 horizontal. Horizontal beams at least 1.5 m wide should be provided at every 3 m depth interval. If excessive sloughing or caving occurs, the slopes may be flattened further to ensure stability.
DEWATERING:
The excavations for the Mall building shall extend to 9~10 m depth. Groundwater was met at 10.2 ~12.3 m depth (RL 86.9~88.4 M) during our field investigation. Therefore, depending upon the season during which construction is taken up, some nominal dewatering may be required in order to complete foundation construction under dry condition. This may be done by pumping from suitably located sumps.
FOUNDATION LEVEL PREPARATION:
The area shall be excavated upto the foundation level. All loose soils should be removed and the exposed foundation bearing surface should be watered and compacted properly using rammers/rollers. The surface should then be protected from disturbances due to construction activities so that the foundations may bear on the natural undisturbed ground. For open foundations, we recommend the placement of a 75 to 100 mm thick “blinding layer” of lean concrete to facilitate placement of reinforcing steel and to protect the soils from disturbance.
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6) Bar Binding and Placement of Foundations Steel :-
STEEL REINFORCEMENT:
An RCC structure has to resist 2 types of forces, one is compression and another is tension. Concrete has the tendency to resist compression force but it cannot bear tension. Therefore, we embed steel bars into concrete since steel is good in tension. These bars are provided at tension zones in concrete where concrete has the risk of failure.
BAR BENDING SCHEDULE ( BBS ) :
Bar bending schedule (or schedule of bars) is a list of reinforcement bars in a given RCC work item, and is presented in a tabular form for easy visual reference. This table summarizes all the needed particulars of bars – diameter, shape of bending, length of each bent and straight portions, angles of bending, total length of each bar, and number of each type of bar. This information is a great help in preparing an estimate of quantities.
WEIGHT OF STEEL BAR:
Let us take a bar of diameter (d) 8 mm and length 1 metre.
Therefore, its weight is given by the following formula-
W = d2/162
W = 82/162 = 0.395 kg or 395 g.
Slab Structure
Slabs are supported on columns and beams. These are horizontal members to live and dead load of buildings.
A one way slab has structural strength in shortest direction.
A two way slab has structural strength in two directions.
A flat slab is a reinforced concrete slab supported directly by concrete columns without the use of beams.
In this project, a thick concrete slab, supported directly on foundations is used to construct the floor for basement no. 2. With addition to this TREMIX (Vacuum Dewatered Concrete Flooring) is done. In this system, concrete is poured in place and vibrated with a poker vibrator. Then a screed vibrator is run over the surface, which is run twice to achieve optimum compression and
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leveling. After this a system of lower mats and top mat is laid on the green concrete and this is attached to a vacuum pump. This draws out excess water.
And the overall slab work is done with flat slabwith Post-Tensioning.
POST TENSIONING :
Post tensioning is a technique for reinforcing concrete. Post-tensioning tendons, which are prestressing steel cables inside plastic ducts or sleeves, are positioned in the forms before the concrete is placed. Afterwards, once the concrete has gained strength but before the service loads are applied, the cables are pulled tight, or tensioned, and anchored against the outer edges of the concrete.
Post-tensioning is a form of prestressing. Prestressing simply means that the steel is stressed (pulled or tensioned) before the concrete has to support the service loads. Post-tensioned concrete means that the concrete is poured and then the tension is applied-but it is still stressed before the loads are applied so it is still prestressed.
Additional benefits are obtained when the post-tensioned reinforcement is installed in a draped profile instead of running in a straight line.
Post-tensioning frequently solves design and construction challenges that other construction methods simply cannot. Some key advantages include:
MATERIAL SAVINGS
Thinner concrete member sizes; reduction in concrete is approximately 20%. Rebar in floor elements is reduced by 60% to 75%.
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Decreased dead load reduces rebar and concrete in columns and foundations. Reduction in building height decreases the cost of building cladding, vertical
mechanical/service elements, and rebar and concrete in shear walls.
INCREASED PERFORMANCE
Improved seismic behavior. Reduced deflection and vibration. Improved crack control and waterproofing properties—especially beneficial for parking
garages and balconies. Longer spans and fewer columns give greater flexibility in floor layouts in
office/residential buildings and better lighting in parking garages which enhances personal safety.
REDUCED LIFETIME COSTS
Lower overall maintenance and lifecycle costs of the structure. Reduced building height also results in energy savings, especially for office buildings.
Equipment used-
Fig: Stretching machine with meter showing load values
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Fig: A labor stretching strands with equipment.
Stretching-
Stretching is done after 7 days of concrete placing means after the concrete has hardened. And then after 2 days, Grouting is done. In grouting, a cement slurry is filled into the duct pipes.
This cement slurry is made by following proportions:
3 bag cement : 300 ml sika (chemical) : 60 litre water.
A force of 400 kg/cm2 is applied by the machine to stretch the strands. The diameter of each strand is 12.7 mm.
A plate called B.G. plate is fixed to the strands before stretching. The duct pipe needs to be locked from one end unless it is too long. In case it is very long, it has to be stretched from both ends.
Sometimes blasting of concrete occurs while stretching. To prevent this, we use a chemical named GP-2.
REINFORCEMENT IN SLAB:
In a slab, there are 2 types of reinforcements provided. The first one is Longitudinal Reinforcement and other is Transverse Reinforcement. Longitudinal bars are the main bars which take the load on the slab. Transverse bars are provided to prevent slab from Shrinkage and effects of Temperature.
Cover block
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Cover blocks are placed to prevent the steel rods from touching the shuttering plates and there by
providing a minimum cover and fix the reinforcements as per the design drawings. Sometimes it
is commonly seen that the cover gets misplaced during the concreting activity. To prevent this,
tying of cover with steel bars using thin steel wires called binding wires (projected from cover
surface and placed during making or casting of cover blocks) is recommended. Covers should be
made of cement sand mortar (1:3). Ideally, cover should have strength similar to the surrounding
concrete, with the least perimeter so that chances of water to penetrate through periphery will be
minimized. Provision of minimum covers as per the Indian standards for durability of the whole
structure should be ensured.
Shape of the cover blocks could be cubical or cylindrical. However, cover indicates thickness of
the cover block. Normally, cubical cover blocks are used. As a thumb rule, minimum cover of 2”
in footings, 1.5” in columns and 1” for other structures may be ensured.
Structural element Cover to reinforcement (mm)
Footings 40
Columns 40
Slabs 15
Beams 25
Retaining wall 25 for earth face , 20 for other face
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Cover block in beam
Things to Note
Reinforcement should be free from loose rust, oil paints, mud etc. it should be cut, bent and fixed
properly. The reinforcement shall be placed and maintained in position by providing proper
cover blocks, spacers, supporting bars, laps etc. Reinforcements shall be placed and tied such
that concrete placement is possible without segregation, and compaction possible by an
immersion vibrator.
For any steel reinforcement bar, weight per running meter is equal to d*d/162 Kg, where d is
diameter of the bar in mm. For example, 10 mm diameter bar will weigh 10×10/162 = 0.617
Kg/m.
Three types of bars were used in reinforcement of a slab. These include straight bars, crank bar
and an extra bar. The main steel is placed in which the straight steel is binded first, then the
crank steel is placed and extra steel is placed in the end. The extra steel comes over the support
while crank is encountered at distance of ¼(1-distance between the supports) from the
surroundings supports.
For providing nominal cover to the steel in beam, cover blocks were used which were made of
concrete and were casted with a thin steel wire in the center which projects outward. These keep
the reinforcement at a distance from bottom of shuttering. For maintaining the gap between the
main steel and the distribution steel, steel chairs are placed between them.
Column Structure
A column is a vertical member in any structure to carry compressive loads. It takes the load from slab & beams and transfers it to the lower slab.
In this project, large no. of columns are constructed since a flat slab is used and no load bearing walls have been constructed. Every column consists of a ‘Drop Panel’.
Drop Panel: The part of a flat slab that has been thickened on the underside at the location of the columns. It distributes the load that is supposed to taken by column.
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Every column should be started with a starter. A starter is provided in order to place the formwork/shuttering in position easily.
Every floor in the mall complex is having total 486 columns.
REINFORCEMENT IN COLUMNS:
Column has 2 types of reinforcements-
1. Longitudinal Bars – They run straight through the column vertically. These are called main reinforcements of column. Diameter of main bar shall not be less than 12 mm. The clear cover requirement for column is 40 mm. Calculation of main bars is done by code IS: 456(2000). And its checking can be done by using Bar Bending Schedule (BBS).Lap is provided in longitudinal reinforcements at the junction of 2 straight bars. Any 2 laps should not come at the same place in column reinforcement. It is said that an Overlap is one of the weakest point in any structure.
Lap is calculated by formula-
53D for M-30 grade concrete and 56D for M-25 grade concrete.
where, D is the diameter of main bar used in column.
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If there are 2 different diameter bars, one of 8 mm and other of 10 mm, then we will find lap by using diameter of larger bar (10 mm).
2. Transverse Bars (stirrup bars or ties) – In order to maintain the position of Longitudinal Bars and also to prevent their buckling which may cause splitting of concrete. The diameter of transverse bars shall not be less than 1/4 th diameter of main bars and in no case less than 5 mm.
Various column sizes used in this project:
450x450, 600x600, 750x750, 750x450, 600x450, 1200x750, 1200x450, 1000x750, 1000x450, etc.
Calculation of transverse bars:
A column needs 2 types of rings for its confinement, the outer ring called Master ring & the inner ring called Star ring.
Cutting Length of Master ring:
Let us take a column of size 750x750 and the diameter (d) of tie bar used is 8 mm.
Cutting length = 4x(750-cover-cover) – (deduction for bends) + (2x10d)
= 4x(750-40-40) – (5xd) + (2x10d)
= 2680 – 40 + 160
= 2800 mm
Cutting Length of Star ring:
Cutting length = 4x(750-40-40)/3 + 4x(316) – (9xd) + (2x10d)
= 894 + 1264 – 72 + 160
= 2246 mm
where, 316 = under root of{2*(670/3)2}
Lift Structure
A Lift is a lifting device consisting of a platform or cage that is raised and lowered mechanically in order to move people from one floor to another in a building.
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Total 19 no. of Lifts are provided in this project.
Fig: Lift reinforcements
Staircase
It is a way of access (upward and downward) consisting of a set of steps.
Each step consists of a Riser and a Tread. Generally the Tread is double times the Riser.
Total 13 staircases have been constructed in this project.
A typical drawing for a staircase constructed in the project:
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STEPS FOR DESIGN OF STAIRS :
1. Measure the height (total rise) of the area where we will install the stairs.2. Divide the height by the typical rise per step. This will give us the total no. of
steps.3. Find the total run of staircase by multiplying tread with no. of steps.4. Now find the length of staircase by using Pythagoras theorem.
7) Shuttering and Scaffolding :-SHUTTERING (FORMWORK):
Formwork is an ancillary construction, used as a mould for a structure. Into this mould, fresh concrete is placed only to harden subsequently. The construction of formwork takes time and involves expenditure upto 20 to 25% of the cost of the structure or even more.
The operation of removing the formwork is known as stripping. Stripped formwork can be reused. Reusable forms are known as panel forms and non-usable are called stationary forms.
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Types of formwork:
1. Timber formwork - Timber is the most common material used for formwork. Timber used for shuttering for exposed concrete work should have smooth and even surface on all faces which come in contact with concrete.
2. Plywood formwork - Resin bonded plywood sheets are attached to timber frames to make up panels of required sizes. The cost of plywood formwork compares favourably with that of timber shuttering.
3. Steel formwork - This consist of panels fabricated out of thin steel plates stiffened along the edges by small steel angles. The panel units can be held together through the use of suitable clamps or bolts and nuts. The panels can be fabricated in large number in any desired modular shape or size. Steel forms are largely used in large projects or in situation where large number reuses of the shuttering is possible. This type of shuttering is considered most suitable for circular or curved structures.
Formwork used in various structures in Mall complex:
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Plywood formwork is used for various structures in Mall complex. Formwork is used in following structures:
a) Formwork for Slab - It is made by interconnecting many plywoods together. For this, they required to be supported by a supporting system called scaffolding.
Scaffolding consists of horizontal and vertical props connected by joints at regular intervals. A jack system is provided at the junction of formwork and vertical props.
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b) Formwork for column - It includes only vertical wooden planks. It has to withstand the live load due to labors, impact while pouring concrete and the thrust due to water (wet concrete).
c) Formwork for Lift walls - Since Lift walls are also to be made of reinforced concrete, they require a particular mould to pour fresh concrete.
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8) Concreting :-
Concrete is a mixture of cement, sand, stone aggregates and water. A cage of steel rods used
together with the concrete mix leads to the formation of Reinforced Cement Concrete popularly
known as RCC.
Concrete has two main stages
1)Fresh Concrete
2)Hardened Concrete
Fresh Concrete should be stable and should not segregate or bleed during transportation and placing when it is subjected to forces during handling operations of limited nature. The mix should be cohesive and mobile enough to be placed in the form around the reinforcement and should be able to cast into the required shape without loosing continuity or homogeneity under the available techniques of placing the concrete at a particular job. The mix should be amenable to proper and through compaction into a dense, compact concrete with minimum voids under the existing facilities of compaction at the site. A best mix from the point of view of campactibility should achieve a 99 When the reinforcement work is finished and a final checking is done by the site engineers, concrete placing will be
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done. The concrete should be of required strength. Concrete of proper design mix is prepared by performing cube test.
Following grades of concrete is used in different structures:
1. M-35 for Slab.2. M-30 for Column.3. M-25 for Staircase.4. M-20 for Beam and Lintel.
Pumping of concrete becomes essential when the structure is tall. In pumping, the concrete of required grade is prepared at the batching plant which is obviously on ground level and then it is pumped to the required height by the system of pipes.
There are some admixtures which can cause segregation while pumping, so care should be taken while using admixture in concrete mix.
FIG: A VIEW OF SLAB CASTING
Formula for compressive strength of cube:
Cast the cube moulds of size of (150mmx150mmx150mm).After curing period of 7 or 28 days, test under compressive testing machine. Then calculate
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result by using formula-
Compressive strength =(load in N)/Area of cube in mm2 (150x150)
Generally compressive testing machine shows load in kN, so we required kN to be converted into N, by multiplying 1000.
For example,Load by machine = 300 kN
Area of cube = 22500 mm2
Compressive strength = 300x1000/22500 = 13.33 N/mm2
Alternatively, the formula becomes-
Compressive strength = {load by machine/22.5}
Inverted beam:
An inverted beam has its bottom same as slab and projecting from the top side by 1/3rd or more of slab thickness.
It is used to give support to the glass to be fixed in the opening. Every glass will be projecting outside of slab by 150 to 200 mm.
percent elimination of the original voids present.
Segregation
The stability of a concrete mix requires that it should not segregate and bleed during the
transportation and placing. Segregation can be defined as separating out of the ingredients of a
concrete mix, so that the mix is no longer in a homogeneous condition. Only the stable
homogeneous mix can be fully compacted
The segregation depends upon the handling and placing operations. The tendency to segregate,
amount of coarse aggregate, and with the increased slump. The tendency to segregate can be
minimized by:
a.Reducing the height of drop by concrete.
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b.Not using the vibration as a means of spreading a heap of of concrete into a level mass over a large
area.
c.Reducing the continued vibration over a longer time, as the coarse aggregate tends to settle to the
bottom and the scum would rise to the surface.
d.Adding small quantity of water which improves cohesion of the mix.
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Concreting
Bleeding
Bleeding is due to the rise of water in the mix to the surface because of the inability of the solid
particles in the mix to hold all the mixing water during settling of particles under the effect of
compaction. The bleeding causes formation of a porous, weak and non durable concrete layer at
the top of placed concrete. In case of lean mixes bleeding may create capillary channels
increasing the permeability of the concrete. When the concrete is placed in different layers and
each layer is compacted after allowing certain time to lapse before the next layer is laid, the
bleeding may cause a plane of weakness between two layers. Any laitance formed should be
removed by brushing and washing before a new layer is added. Over compacting the surface
should be avoided.
Hardened Concrete
One of the most important properties of the hardened concrete is its strength which represents the
ability if concrete to resist forces. If the nature of the force is to produce compression, the
strength is termed compressive strength. The compressive strength of hardened concrete is
generally considered to be the most important property and is often taken as the index of the
overall quality of concrete. The strength can indirectly give an idea of the most of the other
properties of concrete which are related directly to the structure of hardened cement paste. A
stronger concrete is dense, compact, impermeable and resistant to weathering and to some
chemicals. However, a stronger concrete may exhibit higher drying shrinkage with consequent
cracking, due to the presence of higher cement content.
Some of the other desirable properties like shear and tensile strengths, modulus of elasticity,
bond, impact and durability etc. are generally related to compressive strength. As the
compressive strength can be measured easily on standard sized cube or cylindrical specimens, it
can be specified as a criterion for studying the effect of any variable on the quality of concrete.
However, the concrete gives different values of any property under different testing conditions.
Hence method of testing, size of specimen and the rate of loading etc. are stipulated while testing
the concrete to minimize the variations in test results. The statistical methods are commonly used
for specifying the quantitative value of any particular property of hardened concrete.
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Compressive Strength
The compressive strength of concrete is defined as the load which causes the failure of specimen,
per unit area of cross-section in uniaxial compression under given rate of loading. The strength
of concrete is expressed as N/mm2. The compressive strength at 28 days after casting is taken as
a criterion for specifying the quality of concrete. This is termed as grade of concrete. IS 456 –
2000 stipulates the use of 150 mm cubes.
Tensile Strength
The concrete has low tensile strength; it ranges from 8-12 per cent of its compressive strength.
An average value of 10 per cent is generally adopted.
Shear Strength
The concrete subjected to bending and shear stress is accompanied by tensile and compressive
stresses. The shear failures are due to resulting diagonal tension. The shear strength is generally
12-13 per cent of its compressive strength.
Bond Strength
The resistance of concrete to the slipping of reinforcing bars embedded in concrete is called bond
strength. The bond strength is provided by adhesion of hardened cement paste, and by the
friction of concrete and steel. It is also affected by shrinkage of concrete relative to steel. On an
average bond strength is taken as 10 per cent of its compressive strength.
Facts about Cement and Concrete
1) Water required by 1 bag of cement is something in the range of 25-28 liters
2) Quality of concrete has nothing to do with its color.
3) The mortar / concrete should be consumed as early as possible after addition of water to it.
The hydration of cement starts the moment water is added to it. As the hydration progresses the
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cement paste starts stiffening and loses its plasticity. The concrete should not be disturbed after
this. Normally, this is about 45 – 50 minutes.
4) MPa is abbreviated form of mega Pascal, which is a unit of pressure. 1 MPa is equivalent to a
pressure of 10Kg /cm2. The strength of concrete & cement is expressed in terms of pressure a
standard cube can withstand. The Ordinary Portland Cement, commonly called OPC is available
in three grades namely 33, 43 & 53 grades. Thus, for 43 grade cement standard cement & sand
mortar cube would give a minimum strength of 43 MPa or 430 Kg /cm2 when tested under
standard curing conditions for 28 days.
Compressive Strength of Concrete depends on following factors
(i) w/c ratio
(ii) Characteristics of cement
(iii) Characteristics of aggregates
(iv) Time of mixing
(v) Degree of compaction
(vi) Temperature and period of curing
(vii) Age of concrete
(viii)Air entertainment
(ix) Conditions of testing
Precautions for water to be used in concrete
• It is good to use potable quality of water.
• It should be free from impurities and harmful ingredients.
• Seawater isn’t recommended.
• The water fit for mixing is fit for curing too
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• Use of minimum quantity of mixing water, consistent with the degree of workability required
to enable easy placing and compaction of concrete, is advisable.
• Ensure that water is measured and added.
• Low water to cement ratio is essential for good performance of the structure in the long run.
Common Reasons for lack of quality in concrete work
• Use of too much or too little water for mixing, or water carelessly added during mixing
• Incomplete mixing of aggregate with cement
• Improper grading of aggregates resulting in segregation or bleeding of concrete.
• Inadequate compaction of concrete
• Using concrete which has already begun to set.
• Placing of concrete on a dry foundation without properly wetting it with water.
• Use of dirty aggregate or water containing earthy matter, clay or lime.
• Too much troweling of the concrete surface.
• Leaving the finished concrete surface exposed to sun and wind during the first ten days after
placing without protecting it and keeping it damp by proper methods of curing.
Construction joints are the joints provided between successive pours of concrete that have been
carried out after a time lag. As far as possible the construction joints should be avoided and every
care should be taken to keep their numbers minimal. Since, presence of these joints creates a
plane of weakness within the concrete body, these joints should be preplanned and their location
should be such that they are at places where they are subjected to minimum bending moment and
minimum shear force.
Pouring and consolidation
Concrete (M20) was used for all works in column, beams and slabs. It was well consolidated by
vibrating using portable mechanical vibrators. Care was taken to ensure that concrete is not over
vibrated so as to cause segregation. The layers of concrete are so placed that the bottom layer
does not finally set before the top layer is placed. The vibrators maintain the whole of concrete
under treatment in an adequate state of agitation, such that deaeration and effective compaction
is attained at a state commensurate with the supply of concrete from the mixers. The vibrator
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continue during the whole period occupied by placing of concrete, the vibrators being adjusted
so that the centre vibrations approximate to the centre of the mass being compacted at the time of
placing. Shaking of reinforcement for the purpose of compaction should be avoided. Compaction
shall be completed before initial setting starts i.e. within thirty minute of addition of water to the
dry mixture.
The concrete was deposited in its final position in a manner to preclude segregation of ingredients.
In case of column and walls, the shuttering was so adjusted that the vertical drop of concrete is
not more than 1.5 m at a time. In case of concreting of slabs and beams, the pipe from the
batching plant was directly taken to the closest point.
Compaction
Green concrete has all the three phases – solids, water & air. In order to make the concrete
impervious & attain its maximum strength it is required to remove the entrapped air from the
concrete mass when it is still in plastic state. If the air is not removed completely, the concrete
loses strength considerably. It has been observed that 5% voids reduce the strength by about 30%
and 10% voids reduce the strength by over 50%. Compaction eliminates air bubbles and brings
enough fine material both to the surface and against the forms to produce the desired finish. One
can use such hand tools as steel rods, paddling sticks, or tampers, but mechanical vibrators are
best. Any compacting device must reach the bottom of the form and be small enough to pass
between reinforcing bars. Since the strength of the concrete member depends on proper
reinforcement location, be careful not to displace the reinforcing steel.
Compacting reinforced concrete work is very important and is done using iron rods. In case the
thickness of concrete layers should be more than 15 cm. the most satisfactory method for
compacting concrete properly is to consolidate each layer separately so that its top surface
become level and fairy smooth before the next layer is placed. While tamping is carried out, care
should be taken that the rod should penetrate the full layer of the last layer placed and to some
extent into lying to ensure proper bond between bond between them. Secondly the reinforcement
and formwork should not be disturbed from their positions.
Mechanical Compaction
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Mechanical compaction is done by the use of vibrators. Compaction of concrete by vibration is
considered essential for all important works especially in situations where reinforcements are
congested or the member is required is to have exposed to concrete surface finish. When
vibraters are used leaner but stiff, concrete mix should be used to obtain greater durability and
highest strength, mixes which are to stiff to consolidate by hand compaction can be easily
compacted by mechanical compaction, in case the concrete is compacted by vibrations ,during
which the vibrator communicates rapid vibrations to the particles, increases the fluidity of
concrete. Due to vibrations the particles occupy a more stable position and concrete fills all the
space and present is force out to the surface, resulting in dense and durable concrete.
Types of vibrators
Following are the type of vibrates usually used to compact concrete:
1. Internal vibrators
2. External vibrators
3. Surface vibrators
4. Vibrating table
Internal vibrator consists of metal road like vibrating head which is immersed in the full depth of
concrete layer. It is also known as poker or needle vibrator and is consider to be most effective
type of vibrator as it comes into intimate contact with concrete. External vibrators are placed
against the concrete form-work and vibrating force for compaction is conveyed to the concrete
through the form work. These vibrators are also called form vibrators. The vibrator is rigidly
clamped to form work resting on a elastic spot, so that both the form and concrete are vibrated.
Incase considerable proportion of work done is consumed in vibrating resulting in low efficiency
of the system. Surface vibrators are mounted on platform and are generally used to compact and
finish bridge, road slab etc. These are also external vibrators and are suitable for precast concrete
work. It provides a reliable means of compaction of pre-cast concrete and has the adv of offering
uniform vibration. Vibrating table is used for consolidation of pre-cast units. Surface vibrators is
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used there a wide horizontal surface occurs such as dams and very thick walls .large type of
surface vibrators is there but pen type vibrator are used most. When concrete is placed on such
tables, mechanical compaction takes place which has many advantages. Each vibrator have its
own advantages and disadvantages, hence the choice between different types should be made
correctly. Concrete to be compacted by vibration, should be designed properly. The consistency
of concrete depends of conditions of placing, type of mix, and the efficiency of vibrator. The
slum of such concrete should not be more than 5 cm in any case; otherwise segregation of
concrete will take place, which should never be allowed to occur.
Finish concreting work:
a) All concrete while being poured against form work was worked with vibrator
rods & trowels as required so that good quality concrete is obtained.
b) All exposed surface of RCC lintels, beams, columns etc. were plastered to match
with adjoining plastered face of walls after suitably hacking the concrete surface.
Concrete Mixers and Batching Plant
Concrete Plant, also known as a Batch Plant, is a device that combines various ingredients to
form concrete. Some of these inputs include sand, water, aggregate (rocks, gravel, etc.), fly ash,
potash, cement, and other ingredients to create concrete. There are two types of concrete plants,
ready mix plants and central mix plant. A concrete plant can have a variety of parts and
accessories, including but not limited to: mixers (either tilt-up or horizontal (or in some cases,
both), cement batchers, aggregate batchers, conveyors, radial stackers, aggregate bins, cement
bins, heaters, chillers, cement silos, batch plant controls, and dust collectors (to minimize
environmental pollution).
The front view of the plant from where it hauls all the aggregateswhich are used for concreting in
our site is shown in next page:-
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9)
De-shuttering :-
Immediately before concreting is commenced, the formwork is carefully examined to
ensure the following:
a) Removal of all dirt, shavings, sawdust and other refuse by brushing and washing.
b) The tightness of joint between panels of sheathing and between these and any hardened core.
c) The correct location of tie bars bracing and spacers, and especially connections ofbracing.
d) That all wedges are secured and firm in position.
e) That provision is made for traffic on formwork not to bear directly on reinforcementsteel.
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Concrete mixing plant
VERTICALITY OF THE STUCTURE
All the outer columns of the frame were checked for plumb by plumb-bob as the work proceeds
to upper floors. Internal columns were checked by taking measurements from outer row of
columns for their exact position. Jack were used to lift the supporting rods called props
STRIPPING TIME OR REMOVAL OF FORMWORK
Forms were not struck until the concrete has attained a strength at least twice the stress to which
the concrete may be subjected at the time of removal of form work. The strength referred is that
of concrete using the same cement and aggregates with the same proportions and cured under
conditions of temperature and moisture similar to those existing on the work. Where so required,
form work was left longer in normal circumstances
Form work was removed in such a manner as would not cause any shock or vibration that would
damage the concrete. Before removal of props, concrete surface was exposed to ascertain that the
concrete has sufficiently hardened. Where the shape of element is such that form work has re-
entrant angles, the form work was removed as soon as possible after the concrete has set, to
avoid shrinkage cracking occurring due to the restraint imposed. As a guideline, with
temperature above 20 degree following time limits should be followed:
Structural Component Age
Footings 1 day
Sides of beams, columns, lintels, wall 2 days
Underside of beams spanning less than 6m 14 days
Underside of beams spanning over 6m 21 days
Underside of slabs spanning less than 4m 7 days
Underside of slabs spanning more than 4m 14 days
Flat slab bottom 21 days
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10) Electrical and Plumbing Installations :-In every residential and commercial structure, plumbing and electrical installation are the basic needs. Estimated cost of electrical installation is 8% of the total cost of building.
In basements, the electrical installation is done with metal conduits whereas in all other floors, it is done with PVC conduits. Since basement will be used to park vehicles and if in case any fire is caused in basement due to vehicles, the metal conduits will not let damage to the electrical wirings.
11) Masonary and Brickwork :- In the construction of this project, masonry in whole complex is done with fly ash blocks. These blocks are very light in weight, so masonry will be raised a lot easily and the labors will need to put less effort. They are also Sound-proof.
Mortar of cement:sand ratio 1:4 is used in construction of masonry.
Comparison of brick and fly ash block:
Let us take a block of dimensions 200x225x600 mm3.
Hence, volume of block = 200x225x600 = 27000000 mm3
Brick dimensions = 200x100x100
So, volume of brick = 2000000 mm3
No. of bricks in place of 1 block = 27000000/2000000 = 13.5 = 14 bricks.
Cost of 1 brick = Rs. 5
Total cost = 5x14 = Rs. 70 with more labor requirement, more mortar use, more damage, etc.
And cost of 1 block = under Rs. 100
Therefore, use of fly ash block instead of brick is profitable.
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FIG: FLY ASH BLOCK
Reinforcement of diameter 6 mm is provided between joints of masonry after every 3rd layer. It is used to provide support and strength to masonry blocks.
12) Curing :-
The term ‘curing’ is used to include maintenance of a favorable environment for the continuation
of chemical reactions, i.e. retention of moisture within, or supplying moisture to the concrete
from an external source and protection against extremes of temperature
Following are the methods for curing different building parts:-
Walls – Water should be sprinkled from the top such that it covers the whole area of the wall and
it should be remain wet.
Slab – Pounding should be done on the slab by constructing bunds of mortar
Beams and columns – The beams and columns can be maintained wet by tying gunny bags
around the periphery and by maintaining it wet always.
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Pounding, continuous sprinkling, covering with wet cloth, cotton mats or similar materials,
covering with specially prepared paper, polyethylene, sealing coat applied as a liquid commonly
known as ‘curing compound’ which hardens to form a thin protective membrane, are some of the
methods by which concrete is cured. Curing should be started just after the surfaces begin to dry.
Normally 7 to 14 days curing is considered adequate.
ADMIXTURE
Admixtures are those ingredients/materials that are added to cement, water, and aggregate
mixture during mixing in order to modify or improve the properties of concrete for a required
application.
Broadly the following five changes can be expected by adding an admixture
(i)Air entertainment
(ii)Water reduction for better quality
(iii)Acceleration of strength development
(iv)Improving the workability
(v)Water retention
Some of the important purposes for which the admixtures could be used are
1.Acceleration of the rate of strength development at early ages
2.Retardation of the initial setting of the concrete
3.Increase in strength
4.Improvement in workability
5.Reduction in heat of evolution
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6.Increase in durability or in resistance to special conditions of exposure
7.Control of alkali-aggregate expansion
8.Reduction in the capillary flow of water and increase in impermeability to liquids
9.Improvement of pump ability and reduction in segregation in grout mixtures
10. Production of coloured concrete or mortar
The best way to test the admixture is by making trial mixes with the concrete materials to be
used on the job and carefully observing and measuring the change in the properties. This way the
compatibility of the admixture and the materials to be used, as well the effects of the admixture
on the properties of fresh and hardened concrete can be observed. The amount of admixture
recommended by the manufacturer or the optimum quantity determined by laboratory tests
should be used.
13) Placing of Lintels :-Lintels usually are smaller members carrying only the loads immediately above window and door openings.
Height of lintel depends upon the span (length of doorway).
Steel bars are inserted into columns where lintel is to be casted. A chemical named RE-500 is used to insert bars tightly into the columns.
14) Leakage and Water Proofing :-
There are many reasons for leakage in concrete. Due to this leakage, the concrete not only looses
its strength but also cause problem to the user. Normal concrete construction should not require
water proofing materials, if it is designed and constructed properly with good quality and
workmanship. But still to make it safe against the ill effects of water, liquid and powder form of
water proofing material is used depending upon the availability of the material. Normally the
usage per kg of cement is specified by the manufacturer for example: ACC’s waterproofing
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compound “ACCOPROOF” is available in powder form and 1 Kg packets. For normal purposes,
1 Kg is required to be used with 50 Kg (1 bag) of cement.
Leakages occur because of variety of reasons; some of which are mentioned below –
a) Accumulation of water, which start penetrating the surface.
b) Poor quality and improper proportioning of concrete constituents that make concrete
permeable.
c) Poor compaction of concrete, which leave a lot of air voids.
d) Construction joints at two different works like concrete and brick works, and discontinuity in
concrete casting (joint at old concrete and new concrete) leading minute cracks, which facilitate
water movement.
e) Other structural cracks because of loading conditions and failure of the structure to withstand
those stresses.
f) Movement of water from bottom to top because of capillary action.
Following measures may be useful to avoid leakages –
a) Provide good drainage facility with correct gradient at the places where there are chances for
water to accumulate.
b) Use good quality of materials with correct proportioning in concrete. For example, use of
blended cement and use of less water in concrete can reduce permeability of the structure.
Similarly, proper proportioning of materials would help concrete becoming uniformly packed
and dense.
c) Proper compaction of concrete with immersion vibrator to make it void less.
d) Avoid construction joints becoming a weaker point for water to travel. Some proactive and
treatment measures would be useful.
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e) Proper structural design and execution of members, which results no cracks for water to
percolate.
f) Proper damp proofing course required to avoid movement of ground and other water from
bottom to top. Some useful methods are like applying bitumen, concrete construction etc. at
plinth level.
g) Use of water proofing compounds for water retaining structures.
15) Plastering :-Mortar of 12 mm (standard size) and cement:sand ratio 1:6 is prepared for plastering. Plastering is done over masonry walls and column sides. A proper finishing should be given after plastering.
Plaster protects structure from temperature variations; external attacks of sulphates, chlorides,
etc. Plaster also provides smooth & aesthetic surface on RCC & Brickwork surface. The
proportion of mortar used at site for ceiling coat is 1:4 and wall coat is 1:3. A plaster of 10 mm is
done at ceiling and a plaster of 12.5mm is done at wall. Various precautions to be taken while the
work of plastering is going on are:-
•Preferably use cements which releases low heat of hydration.
•Use optimum water at the time of mixing.
•Do not use dry cement on the plaster surface.
•At the junction of Brickwork & RCC, chicken mesh or fiber mesh may be used.
•Wet the surface before plastering and cure the surface for at least 10 to 12 days.
CALCULATION OF CEMENT FOR PLASTER:
12 mm plaster for 10 m2 wall surface will be calculated as following-
Volume of mortar = 10x0.012 = 0.12 m3
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Add 30% to fill up joints, uneven surfaces, etc. = 0.12x1.3 = 0.156 m3
Increase 25% of total dry volume = 0.156x1.25 = 0.195 m3
Hence, for 1:6 cement sand mortar,
Cement = 1x0.195/7 = 0.0278 m3
= .0278x1440 = 40.11 kg
Sand = 6x0.195/7 = 0.167 m3
= 0.167x1780 = 297.5 kg
After we have finished plastering work, painting and other decoration work will be started.
A lot of Glass work is going to be done in this project.
16) Flooring and Tilling works :-
The purpose of a floor is to provide a horizontal sanitary surface to support the occupants of a
building, furniture and equipment. A good floor should have strength and stability, resistance to
dampness, good appearance, and freedom from maintenance etc.
Following are the common floor finishes –
Cement concrete flooring- It consists of 1:1.5:3 cement concrete laid to a thickness of 3” to 4”,
over a strong sub base. Top surface is smoothened with cement punning. It has got good wearing
properties and can be easily cleaned and maintained. If thickness is less, the size of stone
aggregates is limited to ½”. In our site M10 & M15 cement concrete is used in flooring which
consist of 1:3:6 & 1:2:4 respectively.
For roofing M20 cement concrete is used which consist 1:1.5:3 cement concrete laid to a
thickness of 5” to 7” .
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2.3SAFETY EQUIPMENTS1. Safety Belt – It has capacity of 200kg.2. Personal Protective Equipments (PPE) – PPE is anything used or worn by a person to
minimize a risk to a person’s health or safety. It includes Helmet, Eye Goggles, Ear Plug, Nose Mask, Hand Gloves, Safety Shoes, etc.
3. Types of Helmet-
White – for engineers and other high postGreen – for safety departmentRed – for electriciansOrange – for only visit.Blue – for supervisorBlack – for gaurds.Yellow-for workers
4. Fire Extinguisher – It contains CO2 or chemical powder.
Know the PASS system:P = Pull the pinA = Aim at the base of fireS = Squeeze the triggerS = Sweep side to side.
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3.CONCLUSION
During my 6 weeks training, I learnt various things, like the study of architectural drawings (i.e.
plans, elevation and various sections) & structural drawings (i.e. columns, beams, slabs and their
reinforcements). I was questioned on different topics related to construction and whatever I had
gone through and our queries related to the drawings were resolved at the same time.
We had various site visits relating to reinforcement, masonry, concreting of slabs & columns
which made us familiar with the practical aspects in the field.I was also given the technical
literature for study during our site visits and I was also accompanied by experts to the site and all
our queries were solved instantly I co-related the drawings at the sites and whatever we had
studied, with the existing structure .
Also the knowledge gained through paper works at the office has enriched our architectural
concepts. Our various questions on different topics relating to constructions resolved at the time.
It was a wonderful learning experience at Indiabulls Mega Mall Construction Site. I gained a lot of insight regarding almost every aspect of site. The friendly welcome from all the employees is appreciating. I hope this experience will surely help me in my future and in shaping my career.
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