For calculating the quantities of cement,sand and aggregates required for 1㎥ , Let me assume any nominal mix grade of concrete as M-20.(Nominal mix)
Concrete mix design for M-20 (1:1.5:3) grade of concrete:
As we know that when we pour wet concrete during concreting, it hardens after certain standard time. In view of this, it was decided by the Civil Design Engineers to take a factor of safety from 1.54 to 1.57 .
so we can say, Volume of dry concrete = 1.54 to 1.57 times the volume of wet concrete
I m assuming 1.54 as a safety factor
Therefore, the total volume of concrete required is 1.54㎥.
As per IS456:2000, M-20 Grade concrete proportion is = 1 : 1.5 : 3
Remember, here (1:1.5:3) indicates:
1 for cement
1.5 for sand
3 for aggregate
Total volume (cement + sand + aggregate) = 1 + 1.5 + 3 = 5.5
Calculation of Volume of Cement in 1㎥ of Concrete
Volume of cement= (cement/cement+sand+aggregate) x 1.54
Quantity of cement= (cement/total volume) x1.54
= (1/5.5)x1.54
= 0.28 ㎥
we know , Volume of a one cement bag =0.0347 ㎥
Thus Total no. of bags required for 1 ㎥ =0.28/0.0347
= 8 .06 (i.e 8 bags approx.)
Hence, we require 8 bags of cement for 1 cu.m of concrete.
As we know, 1 Bag of cement weighs 50 kg (one bag of cement)
so For 1㎥ of concrete we have ,
Total no. of bags required x 50 kg of cement = 8 x 50 = 400 kg
For 1㎥ of Concrete = 400 Kgs of Cement is required
Calculation of Volume of Sand (Fine Aggregate) in 1㎥ of Concrete:
Volume of sand= (sand/cement+sand+aggregate) x 1.54
Quantity of sand = (sand/total volume) x1.54
= (1.5/5.5)x1.54
= 0.42 ㎥
1㎥ of sand = 1600-1800 kg
Assume 1650 kg
0.42㎥ of sand =1650 x 0.42
= 693 kg
The volume of sand increases as it contains moisture.For accurate calculation use dry sand.
Hence we require 693 kg of sand for 1 cu.m of concrete.
Calculation of Volume of Coarse Aggregate in 1㎥ of Concrete:-
Volume of aggregate= (aggregate/cement+sand+aggregate) x 1.54
Quantity of aggregate= (aggregate/total volume) x1.54
= (3/5.5)x1.54
= 0.84 ㎥
1㎥ of sand = 1500-1800 kg
Assume 1600 kg
0.84㎥ of sand =1600 x 0.84
= 1344 kg
If void spaces decreases,density of aggregate may go higher.
Hence we require 1344 kg of aggregates (20 mm) for 1 cu.m of concrete.
Water required for 1㎥ of concrete: -
Water is added for making the concrete mass and it depends upon the climatic conditions whether hot or cold weather and workability.
We typically maintain a 0.35–0.50 to water cement ratio. Remember, the above values may change according to the moisture content present in the sand and aggregates.
Cement Required for 1㎥of Concrete = 400Kgs
Assume W/C ratio = 0.45
Water required for 1㎥ of Concrete = 400 x 0.45
Amount of water required for 1㎥ of Concrete = 180 kgs = 180 litres.
Hence 180 Litres of Water is required for 1㎥ of M20 Concrete.
Summary: –
8 bags of cement required for 1 cu.m of M-20 grade. concrete.
693 kg of Sand required for 1 cu.m of M-20 grade concrete.
1344 kg of 20mm Aggregate is required for 1 cu.m of M-20 grade concrete.
180 litres of water is required for 1 cu.m of M-20 grade concrete.
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