As we know that during concreting when we place wet concrete , it gets harden after certain standard time( 30 mins IST & 10hrs FST), considering same it had be decided upon by Civil design Engineers to take a factor of safety ranging from 1.54 to 1.57 to counter that shrinkage.
Assumptions
Volume of concrete = 1 m³
Grade of concrete M20 (1:1.5:3)
Find-out the Quantity of concrete (Wet volume and Dry volume)
Wet volume of concrete = 1 m³
Dry volume = Wet volume x 1.54 (You can also take it as 1.50 to 1.55, But it became standard practice to considering 1.54 as multiplication factor).
Dry volume of concrete = 1 x 1.54 =1.54 m³
1- Find-out quantity of Cement
Quantity of cement = (Dry volume of concrete x cement ratio)/(sum of the ratio)
Cement = (1.54 x 1)/(1+1.5+3)=0.28 m³
Density of Cement = 1440 kg/m³
Weight of Cement = 1440 x 0.28 = 403.2 Kg
1 bag of cement contains 50 kg of cement
Number of bags = 403.2 Kg/50 kg = 8.064 ≅8 No’s
2- Find-out quantity of Sand
Cement : Sand :: 1:1.5
Quantity of sand =Quantity of cement x 1.5
Quantity of Sand = 0.28 x 1.5 =0.42 m³
or Quantity of sand =( 1.5/5.5) * 1.54= 0.42 m³
1 m³=35.3147 Cubic Feet (CFT)
Quantity of sand = 0.42 x 35.3147 = 14.832 CFT
Weight of sand = volume x density, Density of Sand = 1650 kg/m^3
Weight of sand= 0.42 x 1650= 693 kg (0.693 tonnes)
3- Find-out quantity of Coarse Aggregates
Cement : Coarse Aggregates :: 1:3
Quantity of Coarse Aggregates =Quantity of cement x 1.5
Quantity of Coarse Aggregates = 0.28 x 3 =0.84 m³
or Quantity of coarse aggregates = (3/5.5)*1.54 = 0.84 m³
1 m³=35.3147 Cubic Feet (CFT)
Quantity of Coarse Aggregates = 0.84 x 35.3147 = 29.664 CFT
Weight of Coarse Aggregates = volume x density, Density of Coarse Aggregates = 1520 kg/m^3
Weight of Coarse Aggregates = 0.84 x 1520 = 1276.8 kg (1.28 tonnes)
The above calculation you can use for all Grade of Concrete but just you have to put the different Grade of concrete like M10, M 15, M20, M25 etc. just here with grade of concrete you can change the proportion and the method is just above which I have discuss .
Different grades of concrete
Different grades of concrete has different Concrete Mix proportions which means different concrete mix ratios. As Per IS456:2000, the Concrete mix design has the following concrete mix proportions :-
Type of Concrete | Concrete Grade | Mix Ratio | Characteristic Compressive strength of Concrete @28Days in N/mm2 |
---|---|---|---|
Ordinary concrete | M5 | 1:5:10 | 5 N/mm2 |
M7.5 | 1:4:8 | 7.5 N/mm2 | |
M10 | 1:3:6 | 10 N/mm2 | |
M15 | 1:2:4 | 15 N/mm2 | |
M20 | 1:1.5:3 | 20 N/mm2 | |
Standard Concrete | M25 | 1:1:2 | 25 N/mm2 |
M30 | Design Mix | 30 N/mm2 | |
M35 | Design Mix | 35 N/mm2 | |
M40 | Design Mix | 40 N/mm2 | |
M45 | Design Mix | 45 N/mm2 | |
M50 | Design Mix | 50 N/mm2 | |
High Strength Concrete | M55 | Design Mix | 55 N/mm2 |
M60 | Design Mix | 60 N/mm2 | |
M65 | Design Mix | 65 N/mm2 | |
M70 | Design Mix | 70 N/mm2 |