PILE CAP

INTRODUCTION

Pile caps are thick reinforced concrete mat which rest on top of

the concrete or timber piles (driven or bored and cast-in-situ) to

provide stability to the foundation. The main objective of constructing

the pile caps is to distribute the load of column(s), which is generally

huge for large constructions, to the under lying piles. A similar type of

foundation to the pile caps are Raft Foundation. In case of Raft, which is

a thick and wide spread RCC slab directly resting at the base of

foundation, loads from columns get directly transported to the soil

strata through the Raft. Raft can only be used for stable hard soil layer

capable to carry huge load without failure. Otherwise Pile and Pile caps

are generally used.

FUNCTION OF PILE CAP

1. To distribute a single load coming from the column to the piles

equally.

2. To laterally stabilize the pile thus increasing the overall

efficiency of the pile group

3. To provide the necessary combined resistance stresses set up

by the super structure and/or the ground movement.

Typical arrangements of piles in pile groups:

Typical shape of pile caps for different number of

piles:

MAIN FEATURES OF PILE CAPS

Minimum grade of concrete that can be used in construction

of piles and pile caps is M25. A complete pile cap can be

casted monolithically in case of smaller pile like for 2-3 piles.

For larger pile caps than those casting is done in layers.

Reinforcement bars of columns are embedded into the pile

caps up to their development lengths.

After casting is done pile caps are cured for 28 days and the

shuttering is removed. The adjacent soil is compacted and

leveled using compactor.

When number of piles in a group is too high, pile caps are

constructed in the form of raft instead of constructing small

pile caps.

Reinforcement caging for a pile cap with 7 piles underneath

PILE CAP CONSTRUCTION AFTER PILES ARE

COMPLETE:

After the completion of DMC piling, the piles are kept for 28

days for curing and the reinforcement bars of the piles are

kept well above the ground level so that they can be easily

traced later.

The surveyor determines the level up to which the soil is to

be excavated to construct pile caps.

The soil is excavated according to that predetermined level

and the upper portions of the piles are then chipped off with

ordinary hammer and jack-hammer. The necessity of this

chipping off of the upper portions of the piles is to get well

compacted concrete piles beneath the pile caps. If the pile

heads were not chipped off, there may have some voids

present in piles below the caps leaving them of little

strength.

The upper portion of piles after excavation up to desired level

Chipping off of the upper ends of the piles

As per design and detailing, the depth of the pile caps are

assured and reinforcement is provided. Sufficient clear cover

is provided using concrete cubes of required dimension,

passing them through the steel bars in definite intervals.

The form work is then completed and concreting is done

monolithically or in layers depending upon the size, depth

and reinforcement density of the pile caps.

BATCHING

PLANT

PROJECT SITE

TCS (TATA CONSULTANCY SERVICE) IT-SEZ PARK

DLF, NEWTOWN, RAJARHAT, KOLKATA,

WESTBENGAL

JOINT VENTURE PROJECT OF L&T AND SPCL

INTRODUCTION

A batching plant is a mechanical system that efficiently mixes and

prepares concrete of desired strength and quality. Cement, coarse

aggregates, sand, water are mixed according to design specifications,

fly ash, admixtures etc are added if required. The whole process is done

mechanically.

Schematic diagram of a concrete batching plant.

Types of batching plant

On the basis of amount of concrete prepared by the plant in unit

time the plants are classified. At the project site the plant in work was

CP30 or Concrete Plant 30. It means that the plant can ideally produce

30 m3 concrete in an hour. There is also CP60 type of plants that are

usually used. It produces 60 m3 concrete in an hour, or 1 m3 concrete in

a minute. So these are also called M1 plants.

COMMON PARTS OF A BTACHING PLANT

CEMENT SILO: These store the cement. There is usually

more than one silo used for a plant to store different kinds

of cements. These are large cylindrical structure with

tapered bottom end connected to the screw conveyor.

SCREW CONVEYOR: this is used to carry the cement from

the silo to the pan mixer.

HOPPER: this is where the front end loader dumps the

aggregates.

BELT CONVEYEOR: this carries the aggregates from hopper

to the aggregates bin.

AGGREGATE STORAGE BIN: These are the conical bins that

temporarily store the aggregates, both coarse and fine and

supply them to the skip bucket.

PNEUMATIC CYLINDER AND DISCHARGE GATE: These are

attached with computerized censors and discharge exact

amount of aggregate into the skip bucket as per mix design

specification.

SKIP BUCKET: it carries the aggregate from storage bin to

the pan mixer.

SKIP BUCKET AND DISCHARGE GATES

PAN MIXER: this is where the concrete is prepared by

mixing all its ingredients. And when the concrete is ready

they discharge the ready concrete into the transit mixer.

ADMIXTUER CHAMBER: admixtures are stored here and

those are conveyed to the pan mixers.

ADMIXTURE CHAMBER

CEMENT FEEDING PUMP: these are used to feed the silo

with cement from the cement storage rooms.

DUST COLLECTOR: this is a chamber that, through a pipe

and pump, collects the harmful cement dust from the

storage room.

DUST COLLECTOR

CONTROL ROOM: this is, from where the whole procedure

is controlled. Computer software is made by the plant

manufactures that also controls the concrete preparation

process. If in case there is any problem the procedures can

be controlled manually too.

SOFTWARE AIDED CONTRLON

WATER VAT: this is a vat located near the plant from where

required amount of water is supplied to the pan mixer

through a pump.

FLOW CHART: BATCING PLANT OPERATION

CONCLUSION TO THE PORJECT

At the project site the plant was aided by one 180kVA and

one 125kVA power generators. Naphtha-base “sikamant-3008NS”

admixtures were being used. For concrete of higher strength (higher

grade than M50) PC-base admixtures are used. The mixing arms inside

the pan mixer are powered by 30Hp motor. Correction shits were

prepared on daily basis to check deviation in strength of concrete due

to variable moisture content of sand.