Area of flat slab = 1000sq.ft = 93sq.m.
The minimum thickness provided for slab is 150mm. (As per IS 456)
150mm = 0.15 metres
Hence Wet volume = Area of slab x Thickness of slab
Wet volume = 93 x 0.15 = 13.95cu.m.
To calculate the quantities of materials we need dry volume
Dry volume = Wet volume x 1.54
[Volume of concrete cube = length x Width x Height = 1 x 1 x 1 = 1m³ (Wet volume)
When we convert this we volume into dry volume, the volume is increased by 54% of wet volume.
∴ Dry volume = Wet volume + 54% of Wet volume
= 1 + (54/100) x 1 =1 + 0.54 = 1.54]
∴ Dry volume = 13.95 x 1.54 = 21.48cu.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}) = 3.90cu.m = 3.90cu.m
We need the quantity of cement in terms of bags.
Unit weight or Density of cement = 1440kg/cu.m.
Quantity of cement in kg(s) = 1440 x 3.90 = 5616kg
We know that 1 cement bag = 50kgs
∴ No. of cement bags required = 5616/50 = 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}) = 5.85cu.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}) = 11.71cu.m
Result:
Cement = 112 bags.
Sand = 5.85cu.m
Aggregates = 11.71cu.m
