At which moisture content (%) is the change in volume (bulking) of sand maximum?
Correct Answer: A. 5%
📚 Detailed Explanation: Moisture Content for Maximum Volume Change in Sand
Why A (5%) is correct: Bulking behaviour of sand follows a characteristic curve: it rises from 0% (dry) to a peak around 4–6% moisture, then decreases as excess water fills voids. The maximum volume change (peak bulking) occurs at approximately 5% moisture content.
Moisture vs. Bulking Relationship
| Moisture (%) | Bulking State |
|---|---|
| 0 | Zero bulking (dry, settled) |
| 2–3 | Rising bulking |
| 4–6 (≈5%) | MAXIMUM bulking (peak of curve) |
| 7–10 | Decreasing bulking |
| >10 | Low/zero bulking |
- Maximum bulking at ≈ 5% moisture.
- Options B (9%), C (12%), and D (15%) are above the peak — at these moisture levels, bulking is declining, not maximum.