Intricacies Simplified

Article 02:
Rev 00 Dated 04.11.2014.
Suppose  together we visit  a construction site .
The RCC slab at the 4th floor is ready for casting tomorrow.
This is how a slab appears prior to casting.
This is how a slab appears prior to casting.

What questions come to your mind ?

1.What kind of materials in what quantity are required for concreting of this slab ?
2.How much time shall be needed to cast this slab ?
3.What are the checks to be done before & during the slab casting ?

Let us see  how do we  solve these questions one by one.

 1.What kind of materials in what quantity are required for concreting of this slab ?

We already know that:

Concrete needs Cement, Sand , Aggregate and water as the basic contents .
Admixtures are also sometimes added depending on specific need.

We already know that the Nominal Mix for Grade M20 concrete is  (1+1.5+3).
For 1 CuM of concrete , the material consumption is as follows:

 ,Cement:   {1.52/(1+1.5+3)} X 28.8 Bags = 7.96 Bags

Sand:          {1.52/(1+1.5+3)}X 1.5 =  0.415 CuM
Aggregate: {1.52/(1+1.5+3)}. X 3  =  0.830 CuM

 2.How much time shall be needed to cast this slab ?

The time taken for casting can be derived as follows:
1.Assuming that each batch is mixed for exactly 1 minute ,then in one hour we can mix concrete using  60 bags of cement.

 2.Suppose the slab  needs 300 bags and we are using only 1 mixer , then we shall need 300/60= 5 hrs.

3.Steps for finding the duration:
3.1.Find out cement to be used.
3.2 Decide no of mixers to be deployed.
3.3 Concreting duration:
(No of cement bags/60)(1/No of mixers).

3.What are the checks to be done before the casting is taken up ?

Checks prior to casting:
Availability of all materials of approved quality in adequate quantity with reasonable lead from the point of mixing.

2.1 Centering plates to be at required level as per drawing.
2.2All gaps properly closed with either wooden planks, GI strips or Masking tape.
2.3.Iron clamps for the Beam & Slab sides.

3.1.Cover blocks in position for slab ( 15 mm ) & beams ( 25 mm).
3.2.Chairs in position for the bent up bars.
3.3.Laps of adequate length
( Slab : 60 X bar dia )
3.4. Recording of reinforcements


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