In a cement concrete work mixed in proportion 1:2:4 by volume, the fine aggregate has a bulking of 10%. If the correction is NOT applied, the actual dry fine aggregate proportion is:
Correct Answer: A. 2 / 1.1
📚 Detailed Explanation: Effect of Uncorrected Bulking on Sand Quantity
Why A (2/1.1) is correct: When sand bulks by 10%, 2 volumes of moist sand contains the solid grains equivalent to only 2 ÷ 1.1 = 1.818 volumes of dry sand. If the batcher fills a gauge box to “2 volumes” using moist sand WITHOUT applying the bulking correction, the mix receives only 2/1.1 ≈ 1.82 volumes of actual dry sand — less than the 2 parts specified. The mix becomes sand-deficient.
Bulking = 10% → bulking factor = 1.10
Moist bulked volume measured = 2 (as specified)
Moist bulked volume measured = 2 (as specified)
Actual dry sand content = Measured volume ÷ (1 + bulking fraction)
= 2 ÷ 1.1 = 1.818 volumes
Sand deficiency = 2 − 1.818 = 0.182 volumes = 9.1% deficit
Correct Approach: Apply Bulking Correction
| Approach | Sand Measured (vol) | Actual Dry Sand (vol) |
|---|---|---|
| No correction (this question) | 2 (moist, bulked) | 2/1.1 = 1.82 🔴 (deficit) |
| With correction applied | 2 × 1.1 = 2.2 (moist, bulked) | 2.2/1.1 = 2.0 ✔ (correct) |
- Uncorrected bulking → actual dry sand = specified volume ÷ (1 + bulking fraction) = 2/1.1.
- Correct volume of moist sand to measure = specified dry volume × (1 + bulking fraction) = 2 × 1.1 = 2.2 volumes.