I. Design Stipulations

• Characteristic compressive strength of concrete required at the site at 28 days (f_ck)=25 MPa
• Maximum size of aggregate = 20 mm
• Shape of coarse aggregate = Angular (Crushed)
• Degree of workability = 100 mm for RCC as per provision made in relevant Indian Standard.
• Degree of quality control = good
• Type of exposure = Moderate

II. Test Data for Materials

• Cement
  • Cement used: OPC
  • Initial setting time of cement = 30 minutes
  • Final setting time of cement = 590 minutes
  • Specific gravity of cement = 3.15
  • Fineness value of cement = 4 % (As per IS 4031 part 1)
  • Soundness of cement = 6 mm (As per IS 4031 part 3)
  • Standard Consistency = 32 %
• Coarse Aggregate
  • Specific gravity of coarse aggregate = 2.72 (IS 2386, part 3)
  • Water absorption of coarse aggregate = 0.7%
  • Free (surface) moisture percent on coarse aggregate = nil
• Fine Aggregate
  • Specific gravity of fine aggregate = 2.67 (IS 2386, part 3)
  • Water absorption = 1.5 %
  • Free (surface) moisture percent on fine aggregate = nil
• Admixture
  • Admixture Used: Superplasticizer (Water Reducer)

III. Sieve Analysis of Aggregate

• Coarse aggregate (20mm Size and Down)
  • 5 kg has been taken for sieve analysis. The result is tabulated as below:

• Coarse aggregate (20mm Size and Down)
  • 5 kg has been taken for sieve analysis. The result is tabulated as below:

• Fine aggregate
  • 1 kg has been taken for sieve analysis. The result is tabulated as below:

M25 design of mix is to be carried out as per IS 10262:2019.

• Mix Design Calculations
• Target mean strength of concrete: (f_m) = f_ck + k × s
  • Where f_ck= 25 MPa (given)
  • k = 1.65
  • s = 4 (from table 2 of IS 10262:2019)
  • f_m = 25 + 1.65 x 4
  • = 31.60 MPa
• Approximate Air Content
  • As per IS: 10262-2019, From Table 3, the approximate amount of entrapped air to be expected in normal (non-air-entrained) concrete is 1.0 percent for 20 mm nominal maximum size of aggregate.
• Selection of Water Cement Ratio (W/C):
  • For moderate exposure, maximum water cement ration (as per table 5 of IS 456-2000) = 0.5
  • Based on experience adopting W/C as 0.45.
• Selection of Water content:
  • Using Table 4 of IS 10262-2019:
  • Maximum water content = 186 kg (20 mm maximum aggregate size)
  • Estimated water content for 100 mm slump = 186 + (6/100) × 186 = 197.16 lit.
  • As Superplasticizer is used, the water content may be reduced by 23 % (as per experience).
  • Hence, water content = 151.81 kg.
  • Adopting 152 kg.
• Determination of cement content:
  • W/C ratio = 0.45
  • Cement content = 151.81/0.45 = 337.36 kg per cum of fresh concrete
  • Minimum cement content for moderate exposure in case of M25 (as per Table 5 of IS:456-2000) = 300 kg/m³.
  • Therefore, adopting 337.36 kg of cement.
• Determination of proportion of aggregate:
  • From Table-5 of IS 10262-20019, the volume of coarse aggregate per unit volume of total aggregate for Zone II corresponding to 20 mm maximum size aggregate & w/c 0.50 is equal to 0.62.
  • In the present case water cement ratio is 0.45.
  • As the water cement ratio is lower by 0.05, the proportion of volume of coarse aggregate is increased by 0.01.
  • Therefore, corrected proportion of volume of coarse aggregate for water cement ratio of 0.45 = 0.63.
  • Volume of fine aggregate = 1-0.63 = 0.37
• Mix Calculation:
  • The mix calculation per unit volume of concrete shall be as follows:
  • Volume of concrete = 1 m³
  • Volume of cement = (mass of cement/specific gravity of cement) × (1/1000)
  • = 0.107 m³
  • Volume of water = (mass of water/specific gravity of water) × (1/1000)
    • = 0.152 m³
  • Volume of Chemical admixture = 0.003  
  • Volume of all aggregate = 1- (0.107 + 0.152+0.003) = 0.738 m³
  • Volume of coarse aggregate = 0.465 m³
  • Volume of fine aggregate = 0.273 m³
  • Mass of coarse aggregate = 0.465 × 2.72 × 1000 = 1270.24 kg
  • Mass of fine aggregate = 0.273 × 2.67 × 1000 = 728.91 kg

Coarse aggregate is further divided in to two parts, 60% of 20 mm size and 40% of 10 mm size aggregate.

1. Mass of 10 mm coarse aggregate = 508.096 kg
2. Mass of 20 mm coarse aggregate = 762.144 kg

• Adjustment of Water, Fine Aggregate and Coarse Aggregate:
  • Water absorption of coarse aggregate = 0.7 %
  • Water absorption of fine aggregate = 1.5 %
  • Water correction =
  • Total water = 152 + 19.82 = 171.82 kg
  • Coarse aggregate = 1270.24 – 8.89 = 1261.35 kg
  • Fine aggregate = 728.91 – 10.93 = 717.98 kg