To calculate the
quantity of cement, sand, and aggregates required for a flat slab first we need
to calculate the volume.
Area of flat slab =
1000 sq.ft =93 sq. m.
The minimum
thickness provided for slab is 150mm .( According to IS 456)
150 mm = 0.15
metres
Hence Wet volume =
Area of slab x Thickness of slab
Wet volume = 93 x
0.15 = 13.95 cu. m.
To calculate the
quantities of materials we need dry volume
Dry volume = Wet
volume x 1.54
∴ Dry volume = 13.95 x 1.54 = 21.48 cu.m (approximately).
Generally, M20
grade concrete is predominantly used for construction purposes.
M20 = 1: 1.5: 3
(Cement:Sand:Aggregates) = (a:b:c)
QUANTITY OF
CEMENT:
Quantity of cement = Dry volume x
(a/{a+b+c}
Quantity of cement
= Dry volume x (1/{1+1.5+3}) for M20 grade concrete.
= 21.48 x (1/5.5})
= 3.90 cu.m = 3.90 cu.m
We need the
quantity of cement in terms of bags.
So by multiplying
the quantity of cement with the density of cement, we will the get quantity of
cement in terms of kilograms.
Unit weight or
Density of cement = 1440 kg/cu.m.
Quantity of cement
in kg(s) = 1440 x 3.90 = 5616 kg
We know that 1
cement bag = 50 kgs
∴ No. of cement bags required = 5616/50 kg = 112.32 bags
=112 bags.
QUANTITY OF SAND:
Quantity of sand = Dry volume x
(b/{a+b+c}
∴ Quantity of sand = Dry volume x (1.5/{1+1.5+3}) for M20
grade concrete.
= 21.48 x
(1.5/5.5}) = 5.85 cu.m
QUANTITY OF
AGGREGATES:
Quantity of
aggregates = Dry volume x (c/{a+b+c}
∴ Quantity of aggregates = Dry volume x (3/{1+1.5+3}) for
M20 grade concrete.
= 21.48 x (3/5.5})
= 11.71 cu.m
SUMMARY:
Cement = 112 bags.
Sand = 5.85 cu.m
Aggregates = 11.71 cu.m
Note: ConsiderYield of concrete as 67% &
Wastages of materials = 2%
You can use the same formula for
different mix proportions such as 1:2:4 etc.
Here, we have calculated in cubic
meter unit but you can calculate in cubic feet unit.
