Calculate the volume of sand required for making 3 m³ of concrete with a nominal mix in the proportion 1 (cement) : 2 (sand) : 4 (coarse aggregates).
Correct Answer: B. 1.32 m³
📚 Detailed Explanation: Sand Volume for 1:2:4 Mix
Why B (1.32 m³) is correct: When concrete ingredients are mixed wet, the volume of the resulting concrete is less than the sum of dry volumes of ingredients (voids are filled, particles pack together). The standard conversion factor is dry volume = 1.54 × wet (placed) volume.
Step 1: Dry volume of mix = 1.54 × 3 m³ = 4.62 m³
Step 2: Total ratio parts = 1 + 2 + 4 = 7
Sand proportion = 2/7
Step 3: Volume of sand = (2/7) × 4.62 = 1.32 m³
Complete Ingredient Breakdown for 3 m³ of 1:2:4 Concrete
| Ingredient | Ratio | Volume |
|---|---|---|
| Cement | 1/7 | (1/7) × 4.62 = 0.66 m³ |
| Sand (FA) | 2/7 | (2/7) × 4.62 = 1.32 m³ |
| Coarse aggregate | 4/7 | (4/7) × 4.62 = 2.64 m³ |
| Total | 7/7 | 4.62 m³ dry → 3 m³ wet |
- Key formula: Dry volume = 1.54 × wet volume (bulk factor for void-filling in concrete).
- Sand volume for 1:2:4 mix to produce 3 m³ = 1.32 m³.