Bulking is:
Correct Answer: A. Increase in volume of sand due to moisture which keeps sand particles apart
📚 Detailed Explanation: Definition of Bulking
Why A is correct: Bulking = increase in apparent volume of moist sand due to surface tension of thin moisture films that push particles apart. This is the standard definition.
Eliminating Incorrect Options
| Option | What It Describes | Correct Term |
|---|---|---|
| A. Volume increase due to moisture | Bulking (correct answer) | Bulking |
| B. Density increase due to impurities | Not bulking — impurities increase bulk density by filling voids | Contamination effect |
| C. Ramming to minimum volume | Compaction of loose sand | Tamping / rodding |
| D. Compacting of sand | Vibration/compaction to reduce air voids | Compaction |
The Bulking Mechanism in Detail
- Dry sand: particles settle together under gravity → normal bulk density.
- Moist sand (3–6% moisture): thin water films coat particles → surface tension creates inter-particle repulsion → volume increases by 20–38%.
- Saturated sand (water above surface): water fills all voids → no surface tension effect → volume returns to near-dry level.