Report Dmrc

8/11/2019 Report Dmrc

1/29

REPORT

INDUSTRIAL TRAINING

AT

DELHI METRO RAIL

CORPORATION

Submitted By:

Shiv Sagar

Enrolment No: 12215009

B.Tech in Civil Engineering with M.Tech in Structural Engineering

Indian Institute of Technology, Roorkee

Foreword

Formatted:Centered, Space After: 0 p

Line spacing: 1.5 lines


2/29

My training at Delhi Metro Rail Corporation, Delhi has been fulfilling in many ways. One

seldom would encounter such an atmosphere of effective work force and immediate decisionmaking. The system of working under stringent deadlines makes DMRC all the more of an

exemplary and motivational place to work in. The amazing people working at this PSU are not only

extra-ordinary engineers but also very good managers. They know how to get the work done,

properly and on time. Regular visits to the sites and quick paper work only makes all of this

atmosphere an amazing learning experience for a trainee like myself. The system automatically feeds

itself and results are there in front of us. The chain of command is never broken and every person

displays enthusiasm in work and take immense interest in a trainee like me, just so that I walk from

here with a lifetime experience and an invaluable chunk of hard core pragmatic knowledge.

I have made this report myself with the help of my notes which I used to make while I was

on-site or in the testing laboratory. Some reference from the internet has been taken to explain the

laboratory tests. But I have performed them all in my training period.

Acknowledgements

I would like to thank Mr Ravi Ranjan and Mr M.P. Kediyal for providing me with the

opportunity to work as a trainee at DMRC.


3/29

Furthermore, this would not have been a success without the hearty support of Mr Yogesh

Maurya, Mr Santosh Pathak, Mr Deepak Tanwar, and Mr Varun Tandon.

I would also like to thank the engineers and contractors of Arvind Techno Engineers Pvt Ltd

for helping me throughout the training period.

Introduction

There is an immense amount of difference between academic knowledge and its

application in the practical world. In the practical world, one faces a lot of challenges which

cannot be simply solved by the knowledge of some book. It is not about applying perfectly the

technical hinges, but also about managing the whole team and effectively going about the work.


4/29

The engineering aspect of it all comes in between and is incomplete without the managerial

part of the job. The whole project is planned, like the team which is appointed to deal with it.

The hierarchy synchronizes beautifully with the work it is expected to do. There are the junior

engineers and section engineers working at the sights constantly inspecting the nature of work

and its quality. The contractors each day in the morning plan out what portions of work they

are going to complete that day. When it is complete, the engineers from DMRC are called to

check and approve the element and sign the papers which gives them the permission to pour

concrete and complete that piece of work. Above these officials are the Assistant engineers and

the Executive engineers. Their responsibility is much more than just being engineers; they are

the answerable to their Project Managers everyday about the pace and the quality of work that

is being done. When it is necessary they also have to deal with the contractors to get the work

done. They have to come to the site and the JEs and SEs inform them duly about the progress

of work and they plan out the best course of action to be taken that day. Above them is the

Project Manager whose duty is much graver. He is the head of the whole site and responsible

for the activities there.

The whole procedure is well organized. It all starts with a geotechnical survey

conducted by DMRC where experts discuss the path of the rail line and its plan. The soil is

analysed and accordingly paths are laid and a tender is made. Construction companies propose

their whole costs for the contract and an agreement is made. Documents like technical

specification of the work, methodology, contractor requirements are released and the

contractors are to duly follow them. The contractor hires a designer consultancy (ASCInfratech. Pvt Ltd) which then conducts their own survey and propose a design for the metro

line. These design are to be verified by a third party and approved as Good For Construction

(GFC). Only then the construction starts.

One special incident which happened on site was the acquisition of DMRC land by

immigrants from Pakistan. It was a delicate situation and it was of primary importance that it

be carried out silently without gathering much of media attention as this could damage the

image of DMRC. They had to be quietly removed from their spot. Although this activity had

nothing to do with engineering but it was the engineers job to ensure that everything was

proper.

This is how a company successfully works. People should not only be good engineers but

also excellent managers, they should understand the whole concept of billing, because it is they

who pass the bill prepared by the contractors Financial and Planning Department.

My experience here was riveting and a powerful learning experienceone very hard to

forget.


5/29

Contents

S. No. Topic

1 Cover

2 Foreword

3 Acknowledgments

4 Introduction


6/29

5 Piling

6 Pile Cap

7 Crash Barrier

8 Pier Shaft

9 Pier Cap

10 Pedestal

11 Bearing

12 Girder

13 Deck Slab

14 Parapet

15 Ramps

16 Surveying

17 Casting (Pour Card approval)

18 Bar Bending Schedule

19 Heavy Equipment

20 Concrete

21 Safety Check

22

Quality Check23 Laboratory Tests

24 References

Piling


7/29

First 1.5m deep dry boring is done before driving the casing.

Then the verticality, ie the plumb level is checked (1.5m).

DMC (Direct mud circulation piles) method is used.

1.5 ton chisel is inserted into the bore hole and bentonite is applied onto the soil through

impact through ducts which are there on the chisel.

It would take around a day for the chisel to go to a depth of 27mtrs. A pit is also dug out

beside the pile where the muddy water can flow out from the pile so it can be driven. This

way the Bentonite, which is used to prevent collapse of soil from the sides is mixed with the

pile.

After cutting the reinforcement cage is inserted into the hole.

The flushing of soil will be confirmed till the density of mud is less than 1.2g/cc.

The concreting is done using a Tremmie pipe of dia 250mm.

A bottom clearance of 700mm was taken when lowering it.

A concreting funnel with 1.5 to 2 cumec capacity is fitted on the top of the Tremmie.

When the first batch of concrete is poured there is a plug used to block the funnel, so that a

large amount of concrete goes inside at once to reduce irregular concreting and voids.

An onsite slump of 150 to 175mm was allowed.

All the time when concreting is done, it is ensured that the tremmie remains at a level 3m

below the top level of concrete.

M35 grade concrete was used.

Pile Cap


8/29

The designer gives the shape of the pile cap. It can be rectangular, hexagonal, pentagonal.

This also depends on the no. of piles which it is going to mount, ehich inturn depends on the

mount of load that pier shaft is going to take.

The procedure here is standard. Before the cap is constructed, its survey is done and points

where it is actually going to stand. The levelling is done.

Then according to the drawing that the contractor has, the Bar Bending Schedule is prepared

and those rebars are made on site. They are tied together using tie bars 8mm dia and the

whole reinforcement cage is made on the top of the pile.

Then again the survey is done from the bench mark and levelling and coordinates of three

visible points are verified with that which were calculated initially theoretically.

The engineer from the client side approves the BBS and allows the contractor to order

concreting.

Crash Barrier

Crash barriers are a kind of a cover given to the pier shaft which protects the concrete from

damage from traffic collision. Mostly those piers which are close to roads are given the crash

barriers.

A small space is left between the shaft and the barrier and thermacol or any other flexible

material is inserted there so that in case of impact it can be effectively absorbed and

consumed and the pier remains safe.

Pier Shaft


9/29

After completion of pile cap, the piers reinforcement is tied as per drawing. A starter of

700mm is made before shuttering is placed.

The bottom of the starter has to be cleaned before casting it. The soil needs to be removed to

provide good bonding.

After 12 hrs. of casting of the starter, the shuttering of the pier shaft is placed.

To prevent bleeding, or leakage of slurry, the joints between the shuttering are filled with

foam or putty.

After the shuttering is placed, a boom placer is used to do the concreting.

De-shuttering after 12 hours and the concrete is covered with hessian clothes which are moist

to prevent perfect curing.

A lot of precautions are taken in curing. Especially during summers. At least 15 days of non-

stop curing is required.

However it is not humanly possible to achieve this, so curing is done every hour using a hose

pipe with good water flow.

It can sometimes take two to three rounds of concreting, when the height of the pier is too

much. Because the shaft is self-compacting, first a slump of 135 to 150mm is given on site

and second a small height is cast each time. Eg 5 metres in one time.

Between one casting and the next one, a construction joint is made. It is kept rough to ensure

proper bonding.

Also curing is recommended by using a hose pipe sprinkled instead of just keeping it at a

place. The concrete becomes red due to rusting that way. It is aesthetically nondesirable.


10/29

Another important thing is the use of coupler joints or lapping when the height requires to

rebars to be joined together. First the designer specifies forbidden areas for lapping and then

at the place where lap is made, it is to be staggered. We dont want any of the points in our

shaft (which is the most important load bearing member (M-55 grade)) to have any weak

points in it.

Pier Cap

Shuttering of the pier cap begins when the shaft has been casted. Staging has been done with

cribs and bracings. Staging should be made up to bottom of pier cap such that the bottom

shutter of pier cap has to be placed properly.

After completion of staging the bottom of pier cap are placed and fixed as per line and

survey.

The reinforcement of pier cap can be started only after completion of bottom shutter.

The reinforcements of the pedestal and seismic arrestor are placed along the cap but cast

later.

The end stopper and side shutter placed after the completion of reinforcements.

During casting vibration and level of casting has to be maintained. A needle vibrator is used

for this purpose. It compacts the concrete well and removes the air cavities.

De-shuttering of side shutters is carried out after 24 hours of casting.

Curing is started the next day of casting.

Pedestal and the Seismic Arrestor


11/29

The pedestal is one of the most important structural members of the structure.

It bears the load of the girder directly.

It is made of concrete of grade M-55.

It is made L-shaped because the girder is not attached to it and it may fall of due to lateral

disturbances during strong wind or an earthquake.

The whole structure here is made to resist an earthquake of magnitude of X on the Richter

scale.

The Seismic arrestor on the other hand prevents the movement of the girder in the

longitudinal direction. It is also called the longitudinal re-strainer.

The pedestal is cast after the pier cap is casted with a cover of 40mm to it.

But the seismic re-strainer is casted after the girders are placed and the deck slab casted. This

is because if there are any adjustments to be made later then they can be made. Once the

arrestors are casted, there is no room for changes to be made.

Bearing and Wedge plate


12/29

The permanent bearings are designed for bearing construction loads, so the permanent

bearings are installed at a later stage.

The span weight is then made to be transferred to the bearings.

The vertical level of the bearing plinth must be checked before installing them.

Horizontal adjustments are also made while transferring the span load.

Bearings are positioned with design horizontal, transverse and vertical coordinates.

Before installation the bearings must be cleaned of any grease of dust/sand.

The jack sledge are cleaned of grease and/or sand.

The jacks are placed between the pedestals.

There are four jacks, 200tons capacity each.

The span is brought to the centre line using the jacks.

The gap between the permanent bearing and the soffit of the pier segment is measured from

the four sides.

The gaps are filled by self-compacting non shrinkage gout.

Cubes are taken and compressive strength is tested on them.

After getting the required strength, the permanent bearing is placed above pedestal.

The span is lowered on the bearing and the final survey is done.

Adhesive is applied on the inner surface of the bearings uniformly.

A 12mm steel plate is placed behind the bearing.

Mix of GP2 and 10mm aggregate is made properly.

After attaining the strength, the wooden temporary shuttering is removed.

Girder

In the structure I girders are used instead of segmented spans which are used in many

previous metro spans.

These IGirders are post tensioned, which means they are stressed after casting.

In some girders there are six sets of strands. In some there are only two.


13/29

First of all, their reinforcement cages are prepared and the HDPE (High density polyethylene)

ducts are inserted according to the drawing which specifically provides the coordinates of the

different points.

This is called the profile of the girders which is checked and approved by the engineer.

The plies are of high tensile steel.

Sheathing pipe is made of HDPE.

Tensioning is done 7 days after curing.

Anchor cone is made of grey cast iron and allows for transfer of force from bearing plate to

concrete. The design allows free injection of grout. And uniform flaring to the strands.

Bearing plate is made of forges steel. The conical holes hold the strands in stressed position.

Wedges are made of ally steel. The wedge is made of 3 segments tied by a special wire circle

clip for better functioning, easy placement and storage.

The sheathing pipe is held with strands of 16mm dia to get the design coordinates.

It shall be prevented from displacement during concrete with a rebar support to it.

The pipes are connected using couplers and PVC tapes.

It is ensured that the tapered holes are free of rust.


14/29

The designer while specifying the amount to which the strands have to be stressed provides

the E and A. but if the manufacturing is quite different, then we have to change the amount of

elongation.

New extension = (design extension) x (EA)/E`A`). So if the E and A are increased, then the

elongation is decreased because the strands are much more stronger now.

Then another adjustment due to slipping when the wedges are locked is provided (usually

6mm).

This gives us the new allowable extension with a variation of 5% either way.

If our elongation does not reach this level then P can be increased 1.05 times.

During tensioning no person should be standing in front of the jack. If it loosens and slips, he

willbe shredded.

Wax is applied inside holes and outside of master grip.


15/29

Cutting is carried out 24hrs after slip loss. It should be cut 40mm from the face.

End sealing is done with grout cap or epoxy and cement mortar.

Inner surface of grout cap had grease applied to it.

Grouting is done to protect steel from rust and to form effective bond between pre-stressing

cables and concrete.

For grouting OPC is used and a w/c ration is kept between .40 and .45.

The temperature is maintained at 19 degrees by addition of ice to the water.

Admixture Cebex 100 is used to improve workability and reduce shrinkage in the grout.

Grouting is done as early as possible when the stressing is completed.

First cables will be cleaned with water.

Mixing of grout is done for 1 min.

The agitator is placed at a height so that the mortar can flow to the top the second tank placed

below the agitator.

While pouring it is passed through a 2mm mesh which eliminates lumps and reduce choking

of grout pipe.

Always ensure that there is enough grout in the tank so that the air does not flow into the

pipe.

A pressure of 3-5 kg/sqcm is used to induce grout.

An epoxy coat is applied on the anchorages to prevent damage.

While concreting, vibration is of utmost importance for the girder.

There are shutter vibrators placed on the false work so that the concrete is compacted easily.

Bleeding is also stopped by foaming the joints.

A slump of 90 to 120mm is allowed for the girder.

Deck slab


16/29

After the girders have been erected, the deck slabs rebar cage is tied as per the drawing.

First the bottom level shuttering is put in place which is made of a plywood of thickness

16mm.

In the survey of the deck slab, first the level of the various points on its profile are checked.

They are checked normally at a distance of 3m across.

Then the centre line is also checked.

A portion of the deck slab was cut out to make space for the man hole. Between two deck slabs there is an expansion joint. The span cannot be I any case more than

around 30m without an expansion joint in between.

The expansion joint consists of a pair of steel strips screwed to the ends of the deck slab.

Then a rubber sheet is provided over them to make it damage resistant.


17/29

Note that at all the places, the system is earthed. Throughout the pile cap, shaft, pier cap, slab

and the rails.

The two slabs are also connected with a galvanized omega shaped strip to provide flexibility.

Another thing is that at the end to make space for pre-stressing of girders, the slab is jack-

hammered at the expansion joint to make space for the jack to hang.

A concrete of M-50 grade is poured on the slab using a boom placer. It is case-on-site.

The girders are pre-cast.

The drain pipe goes down along a hole carved inside the pier shaft.

Another notable aspect here is that the top of the girder which is cast along with the deck is

not smoothed out.

A construction joint is formed here, so it is kept rough and rugged so that there is little space

for weakness. Moreover there are rebars coming out of the girders which are themselves cast

with the slab.

Also there are rebars protruding from the slab which are going to be the rebars for the

backbone of the railway tracks.

The base of the tracks this way would be fully reinforced.

This eliminates the need of ballasts in the track system in the Metro.

This base would be L shaped and the tracks will be on the lower base.

However this is true for the viaduct. But when the train runs on the ground (ie the depot

Mukundpur) then rock ballasts will be used, like in Yamuna Bank station.

The deck is kept tapered at its ends as the designer wants it.

Parapet and Parapet stitching

The parapets serve the purpose of being the base for the Over Head tension electricity cables.


18/29

There contribute little to the structural stability of the viaduct and rather contribute

aesthetically because these are the units which are going to be visible to the public and they

will be having the DMRC logo embedded on them.

They will be how the people will be the Delhi Metro.

Their alignment is very important for the reasons mentioned above.

They are M-45 grade pre-cast units placed with the help of cranes on the deck.

They are just kept there and attached using turn buckles until they are stitched together with

the desk slab.

They are placed on two humps on the inner side of the curvature.

They can be adjusted using the turn buckles when the surveying is done to ensure correct

levelling and their alignment with the centre line.

This alignment is done by using a plumb bob and a tape.

At a distance of 3m there ate marks made by the surveyor on the deck slab where the plumb

is reached and it is verified if this is the mid-point or not.

After stitching there would be no provision to move the parapets so all adjustments are made

beforehand.

The grade of the stitch concrete is M-45. Its just regular concrete but termed stitch concrete.

The stitch has a rectangular cross section and it stitches the rebars protruding from the parapet

to that of the deck slab, like that in the case of the girder.

Before stitching the two rebar arrangements are bound together using binders which 12mm

dia rebars.

Ramps


19/29

In CC14, there are ramps at two places. One comes up from Azadpur underground and one

lands onto the Mukundpur depot.

There are six types of ramps here which are categorized on the basis of taper, width strength

of foundation etc.

Basically they are supported by a base raft foundation having reinforced cement concrete.

This foundation has a span of around 27m for one type of ramp.

On the top of the ramp, there are walls with a hunch at their bottom.

These are thick walls with 50mm covers. On the top of the wall, there is another hunch and

then a roof.

This roof does the analogous work of the deck slab for the viaduct. The space in between is

filled soil and the foundation is complete.

Above this as usual the parapets are placed and stitched.

Surveying

Surveying, throughout the construction work and also before remains one of the most

important aspects that should be kept in mind.

Before the project was even given to the contractor, a geotechnical survey was conducted to

analyse the soil, its properties and predict where the metro line should be made to run.

Different plans are made and the land is bought.

After this is done GPS is used to set up bench marks and levels are calculated of each and

every point on our structure.

The contractor is hired and they in turn hire a design consultancy which conducts its own

survey. These people then give the specific details of level and construction.

During the construction of each and every part of the system, first the survey is checked by

the engineer, then only is it cast.

The shuttering cannot be placed without proper survey reports.

Survey was done using a total station and its prism. Some places also auto level used.

Casting

Casting or concreting of the structure marks its end. It is the final aspect of construction and

practically irreversible for the contractorespecially in terms of its feasibility.

During concreting, for each TM, the slump (on site and at the casting yard) is checked.

It should lie in limits.


20/29

Also six cubes are casted at site so that their strength can be tested in the laboratory after 7

days and 28 days (3 each).

If the cubes later on fail, then more tests are conducted on site.

If all tests fail, then the structures casting is demolished.

So before the casting is done everything has to be approved by the engineer this is the list of

things to be done by him:

(a)Survey Report: Survey report has be approved by the engineer when the survey It

was performed in front of engineer by the surveyor.

(b)Safety checklist

(c)Reinforcement Inspection

(d)False Work

(e)Concreting Arrangement

(f)

Pour Card: This is very important and is filled by the engineer during concreting.

The value of slump is noted and checked if it lies in our limit.

(g)Post inspection

(h)Bar Bending Schedule

(i) Photograph


21/29

(j) Batch Report: The batch report contains the batches which were poured into the

transit mixer and their respective times. They also have their amounts of cement

aggregates, water, sand and admixture contents in mass.

In case of Pile Cap, Pit Test is also included.

Bar Bending Schedule

The engineer on the contractors side prepares a BBS according to the drawing of the

structure provided to him by the designer.

The BBS contains the details of all the rebars that are going to be included in the cage of the

structure.

The details include the diameters, the quantity, centre to centre distance, the shape, cutting

length, the diagram showing its extra length cuts and their total quantity.

The engineer has to check the BBS along with the contractor applying the calculations that

the contractor did to achieve this BBS.

The BBS is approved by the engineer after all verifications and the order to cut the rebars is

given then.

Heavy Equipment used in construction

JCBs: Bulldozers to excavate and demolish

Hydras: These are used to place laddrs to place false works on viaduct etc. their reach is

much higher than JCBs

Cranes: Cranes are used to lift parapets, girders, rebars for high piers (17m?)

Boom Placer: The Boom Placer has the ability to concrete at a height of 40m. Almost all of

the concreting for viaducts including precast girders is achieved through a Boom Placer.

Gantry cranes: The Gantry is located at the camp where there are 2 cranes each of 75 Metric

Ton capacity. They are used to lift girders, their form work, cables etc.

Transit Mixers: They are used to carry concrete from the batching plant to the site.


22/29


23/29

Concrete (Technical Specifications)

Cement:

53 grade OPC.

Ambient Atmospheric temp maintained.

Tests: Consistency, initial setting time, final setting time.

Compression test: cubes of 70.6mm side.

Fine aggregate: river snad pit sand, stone dust etc.

No loam, clay, silt, vegetable matter.

Has hard siliceous matter.

Chlorides, silt, clay need to be removed.

Coarse aggregate:

Gravel, annular, hard, dense, free from soft, thin, friable or flaky material.

Flakiness and elongation test are done on them.

Water used is potable, free of any chemical like chlorides which would cause corrosion.

Safety visit

Every Thursday, safety visit is conducted where safety officers from DMRC come and carry

out an inspection of the site for the safety of the labour working.

They check the equipment in use, their proper earthing, and ladders for climbing on high

piers.

The safety department of the contractor makes notes and ensures that the following points are

taken care of.

The site is big, so each week a specific area is chosen for safety check.


24/29

Quality Check

Quality check is also conducted by DMRC but it happens in a surprise manner.

It can any day or time.

The quality of cement, concrete, and other materials used is checked.

The laboratory furnishings, the company products, their effectiveness, warranty is checked.

They then take photographs and make a presentation and later on present it.

The measures are taken to make sure that the points mentioned in their report are followed

and taken care of.

LABORATORY TESTS:

Concrete Cube compression test:

Out of many test applied to theconcrete, this is the utmost important which gives an idea

about all the characteristics of concrete. By this single test one judge that whether Concreting

has been done properly or not. For cube test two types of specimens either cubes of 15 cm X

15 cm X 15 cm or 10cm X 10 cm x 10 cm depending upon the size of aggregate are used. For

most of the works cubical moulds of size 15 cm x 15cm x 15 cm are commonly used.

This concrete is poured in the mould and tempered properly so as not to have any voids. After

24 hours these moulds are removed and test specimens are put in water for curing. The top

surface of these specimen should be made even and smooth. This is done by puttingcement

paste and spreading smoothly on whole area of specimen.

These specimens are tested by compression testing machine after 7 days curing or 28 days

curing. Load should be applied gradually at the rate of 140 kg/cm2 per minute till the

Specimens fails. Load at the failure divided by area of specimen gives the compressive

strength of concrete.

Mix the concrete in a laboratory batch mixer.

Clean the mounds and apply oil.

Fill the concrete in the moulds in layers approximately 5cm thick

Compact each layer with not less than 35strokes per layer using a tamping rod (steel bar

16mm diameter and 60cm long, bullet pointed at lower end)

Level the top surface and smoothen it with a trowel.

The water for curing should be tested every 7days and the temperature of water must be at 27

deg.
http://theconstructor.org/practical-guide/work-procedure/concrete-work-procedure/http://theconstructor.org/building/building-material/cement/http://theconstructor.org/building/building-material/cement/http://theconstructor.org/practical-guide/work-procedure/concrete-work-procedure/


25/29

Minimum three specimens should be tested at each selected age. If strength of any specimen

varies by more than 15 per cent of average strength, results of such specimen should be

rejected. Average of the specimens gives the crushing strength of concrete. The strength

requirements of concrete.

Here a months data is collected and standard deviation is calculated. If SD is less, the quality

is better. Then using Fck and SD, compressive strength is calculated.

Slump Test:

Slump test is used to determine the workability of fresh concrete. Slump test as per IS: 1199

1959 is followed. The apparatus used for doing slump test are Slump cone and tamping rod.

The internal surface of the mould is thoroughly cleaned and applied with a light coat of oil.

The mould is placed on a smooth, horizontal, rigid and non-absorbent surface.

The mould is then filled in four layers with freshly mixed concrete, each approximately to

one-fourth of the height of the mould.

Each layer is tamped 25 times by the rounded end of the tamping rod (strokes are distributed

evenly over the cross section).

After the top layer is rodded, the concrete is struck off the level with a trowel.

The mould is removed from the concrete immediately by raising it slowly in the vertical

direction.

The difference in level between the height of the mould and that of the highest point of the

subsided concrete is measured.

This difference in height in mm is the slump of the concrete.

Value of Slump can be increased by the addition of chemical admixtures like mid-range or

high-range water reducing agents (super-plasticizers) without changing the water/cement

ratio. This is used to improve workability of concrete.

Once the cone is filled and topped off [excessive concrete from top is cleared] raise the cone

within 5-10 seconds.

The dimensions of the slump cone are:

Top Diameter10cm

Bottom Diameter20cm

Height30cm.

Slump is checked while concreting immediately when the Transit mixer arrives. It should lie

in range, otherwise the TM is rejected.

Allowable values of Slump:


26/29

Pile: 150-175mm.

Pier shaft: 120-155mm.

Rest: 90-120mm.

Flakiness and Elongation Test:

Flakiness Index is the percentage by weight of particles in it, whose least dimension (i.e.

thickness) is less than three-fifths of its mean dimension. Elongation Index is the percentage

by weight of particles in it, whose largest dimension (i.e. length) is greater than one and four-

fifths times its mean dimension.

Flaky and elongated particles may have adverse effects on concrete and bituminous mix. For

instance, flaky and elongated particles tend to lower the workability of concrete mix which

may impair the long-term durability.

This test is not applicable for sizes smaller than 6.3mm.

Sieve the sample through the IS sieves. Take a minimum of 200 pieces of each fraction to be

tested and weigh them.

Weigh the flaky material passing the gauge. In order to separate the elongated materials,

gauge each fraction for length on a length gauge.

Flakiness Index (30% is allowable)=

(Wt. passing through flakiness gauge) / (Total Wt.) x 100

Elongation Index =

(Wt. passing through elongation gauge) / (Total Wt.) x 100

The shape tests give only a rough idea of the relative shapes of aggregates. Flaky and

elongated particles should be avoided in pavement construction, particularly in surface

course. If such particles are present in appreciable proportions, the strength of pavement layer

would be adversely affected due to possibility of breaking under loads. Workability is

reduced for cement concrete.

Aggregate Impact Value Test:

This test is done to determine the aggregate impact value of coarse aggregates as per IS: 2386(Part IV) 1963. The apparatus used for determining aggregate impact value of coarse

aggregates is

Impact testing machine conforming to IS: 2386 (Part IV)- 1963,IS Sieves of sizes12.5mm,

10mm and 2.36mm, A cylindrical metal measure of 75mm dia. and 50mm depth, A tamping

rod of 10mm circular cross section and 230mm length, rounded at one end and Oven.


27/29

The test sample should conform to the following grading:

- Passing through 12.5mm IS Sieve 100%

- Retention on 10mm IS Sieve100%

The sample should be oven-dried for 4hrs at a temperature of 100 to 110oC and cooled.

The measure should be about one-third full with the prepared aggregates and tamped with 25

strokes of the tamping rod.

A further similar quantity of aggregates should be added and a further tamping of 25 strokes

given. The measure should finally be filled to overflow, tamped 25 times and the surplus

aggregates struck off, using a tamping rod as a straight edge. The net weight of the aggregates

in the measure should be determined to the nearest gram (Weight A).

The cup of the impact testing machine should be fixed firmly in position on the base of the

machine and the whole of the test sample placed in it and compacted by 25 strokes of thetamping rod.

The hammer should be raised to 380mm above the upper surface of the aggregates in the cup

and allowed to fall freely onto the aggregates. The test sample should be subjected to a total

of 15 such blows, each being delivered at an interval of not less than one second.

The sample should be removed and sieved through a 2.36mm IS Sieve. The fraction passing

through should be weighed (Weight B). The fraction retained on the sieve sho uld also be

weighed (Weight C) and if the total weight (B+C) is less than the initial weight (A) by more

than one gram, the result should be discarded and a fresh test done.

ii) The ratio of the weight of the fines formed to the total sample weight should be expressed

as a percentage.

Aggregate impact value = (B/A) x 100%

Two such tests should be carried out and the mean of the results should be reported.

Consistency Test:

The basic aim is to find out the water content required to produce a cement paste of standard

consistency as specified by the IS: 4031 (Part 4) 1988. The principle is that standard

consistency of cement is that consistency at which the Vicat plunger penetrates to a point 5-

7mm from the bottom of Vicat mould.

Weigh approximately 400g of cement and mix it with a weighed quantity of water. The time

of gauging should be between 3 to 5 minutes.

Fill the Vicat mould with paste and level it with a trowel.

Lower the plunger gently till it touches the cement surface.


28/29

Release the plunger allowing it to sink into the paste.

Note the reading on the gauge. Repeat the above procedure taking fresh samples of cement

and different quantities of water until the reading on the gauge is 5 to 7mm.

Express the amount of water as a percentage of the weight of dry cement to the first place of

decimal.

A temperature of 27 degrees is to be maintained. High temperature causes loss of water. And

humidity should also be minimized. Laboratory should be closed.

28% is very appropriate.

Initial Setting and final setting test:

Prepare a cement paste by gauging the cement with 0.85 times the water required to give a

paste of standard consistency

Start a stop-watch, the moment water is added to the cement.

Fill the Vicat mould completely with the cement paste gauged as above, the mould resting on

a non-porous plate and smooth off the surface of the paste making it level with the top of the

mould. The cement block thus prepared in the mould is the test block.

Place the test block under the rod bearing the needle. Lower the needle gently in order to

make contact with the surface of the cement paste and release quickly, allowing it to

penetrate the test block. Repeat the procedure till the needle fails to pierce the test block to a

point (3.0 - 5.0) 0.5mm measured from the bottom of the mould.The time period elapsing

between the time, water is added to the cement and the time, the needle fails to pierce the test

block by 5.0 0.5mm measured from the bottom of the mould, is the initial setting time.

Replace the above needle by the one with an annular attachment. The cement should be

considered as finally set when, upon applying the needle gently to the surface of the test

block, the needle makes an impression therein, while the attachment fails to do so. The period

elapsing between the time, water is added to the cement and the time, the needle makes an

impression on the surface of the test block, while the attachment fails to do so, is the final

setting time.

Sieve test:

Sieve analysis helps to determine the particle size distribution of the coarse and fine

aggregates. This is done by sieving the aggregates as per IS: 2386 (Part I) 1963. In this we

use different sieves as standardized by the IS code and then pass aggregates through them and

thus collect different sized particles left over different sieves.


29/29

A set of IS Sieves of sizes 80mm, 63mm, 50mm, 40mm,31.5mm, 25mm, 20mm, 16mm,

12.5mm, 10mm, 6.3mm,4.75mm, 3.35mm, 2.36mm, 1.18mm, 600m, 300m, 150m and

75m.

Balance or scale with an accuracy to measure 0.1 percent of the weight of the test sample.

The test sample is dried to a constant weight at a temperature of 110 + 5oC and weighed.

The sample is sieved by using a set of IS Sieves.

On completion of sieving, the material on each sieve is weighed.

Cumulative weight passing through each sieve is calculated as a percentage of the total

sample weight.

Fineness modulus is obtained by adding cumulative percentage of aggregates retained on

each sieve and dividing the sum by 100.

The results should be calculated and reported as :

i) the cumulative percentage by weight of the total sample

ii) the percentage by weight of the total sample passing through one sieve and retained on the

next smaller sieve, to the nearest 0.1 percent. The results of the sieve analysis may be

recorded graphically on a semi-log graph with particle size as abscissa (log scale) and the

percentage smaller than the specified diameter as ordinate. It is a straight line.

References

The whole methodology has been written from my personal experience and

notes.

Some notes were made from the Technical Specifications file of the contract.

For the Laboratory tests, help from the internet has been taken.

o http://www.engineeringcivil.com/
http://www.engineeringcivil.com/http://www.engineeringcivil.com/