Volume of coarse aggregate per unit volume of total aggregate = 0.62 x 90% = 0.558 Note 2: For pump-able concrete or congested reinforcement the coarse aggregate proportion may be reduced up to 10%. If the coarse aggregate is not angular, the volume of coarse aggregate may be required to be increased suitably, based on experience. If the w/c is more than 0.5, the volume of coarse aggregate is to be reduced to increase the fine aggregate content. If the w/c is less than 0.5 (standard value), volume of coarse aggregate is required to be increased to reduce the fine aggregate content. Note 1: For every ☐.05 change in w/c, the coarse aggregate proportion is to be changed by 0.01. Table for correction in estimation of coarse aggregate proportionĬorrection in Coarse Aggregate proportion Volume of coarse aggregate per unit volume of total aggregate = 0.62 Step 5: Estimation of Coarse Aggregate proportion:-įor Nominal maximum size of aggregate = 20 mm, Hence cement content adopted = 383.2 kg/m 3.
In the present example against mild exposure and for the case of reinforced concrete the minimum cement content is 300 kg/m 3 which is less than 383.2 kg/m 3.
This value is to be checked for durability requirement from IS: 456. Minimum cement Content for mild exposure condition = 300 kg/m 3 Values as per Standard reference conditionĮstimated water content = 186+ (3/100) x 186 = 191.6 kg /m 3 Step 4 - Selection of Cement Content Maximum water content = 186 Kg (for Nominal maximum size of aggregate - 20 mm) Maximum water-cement ratio for Mild exposure condition = 0.55īased on experience, adopt water-cement ratio as 0.5. Step 2 - Selection of water / cement ratio:. S = standard deviation in N/mm 2 = 4 (as per table -1 of IS 10262- 2009) In this case standard deviation is taken from IS:456 against M 20 is 4.0.
Himsworth constant for 5% risk factor is 1.65. Procedure for Concrete Mix Design of M25 Concrete Step 1 - Determination Of Target Strength (e) Fine aggregates confirm to Zone II of IS - 383 (d) Aggregate are assumed to be in saturated surface dry condition. (h) Method of concrete placing: pump able concrete (ii) Test data of material (to be determined in the laboratory) (g) Type of cement: PSC conforming IS:455 (f) Type of exposure the structure will be subjected to (as defined in IS: 456) - Mild (e) Degree of quality control available at site - As per IS:456 (d) Degree of workability required at site - 50-75 mm (slump) (b) Nominal maximum size of aggregate - 20 mm (a) Characteristic compressive strength required in the field at 28 days grade designation - M 25