Example
Let suppose we have a two-way slab having a length of 20 feet and same as the 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 is converted into a wet condition to dry condition and then find out 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.
