**Example **

Let suppose we have a two way slab having a length of 20 feet and same as width of 20 feet and use M-15 grade of concrete, Calculate the quantity of cement ,sand and aggregate that are used in a slab and thickness of the slab is 6 inches?

**Given Data**

Length = 20 feet

Width = 20 feet

Thickness = 7 inches

**Solution**

First, we calculate the volume of the slab and then this volume are converted into a wet condition to dry condition and then find out the how much material is required for the slab.

Total volume of slab = L x W x H

= 20 x 20 x 0.583 = 233.2 cft

Convert wet volume to dry volume

Dry volume = wet volume x 1.54 (Wastage of sand Bulking all included)

= 233.2 x 1.54 = 359.13 cft

Ratio of concrete ( 1:2:4 = 7)

**1- Volume of cement**

Vol. of cement = ratio of cement / total ratio x dry volume

= 1 / 7 x 359.13

= 51.30 cft

convert this volume into cement bags. you know that 1.25 cuf in one cement bag.

= 51.30 / 1.25

=** 41.04 bags.**

**2- volume of sand**

Vol. of sand = ratio of sand / total ratio x volume

= 2 / 7 x 51.30

= **14.65 cft.**

**3- Volume of aggregate**

Vol. of aggregate = ratio of aggregate / total ratio x volume

= 4 / 7 x 51.30

= **29.31 cft.**