Bulking of Sand – compute percentage bulking from height readings In a cylinder test, the depth of moist sand is 15 cm. After full inundation with water, the depth reduces to 12 cm. What is the percentage bulking of the moist sand?

Introduction / Context:
Bulking is the increase in apparent volume of sand due to a thin film of water around particles that causes them to repel and bridge. It is important for volumetric proportioning at site; failure to correct for bulking results in lean mixes and strength loss.

Given Data / Assumptions:

• Apparent depth (height) of moist sand in cylinder, hm = 15 cm.
• Depth after inundation (true volume with no bulking), hs = 12 cm.
• Same mass of sand before and after inundation; readings are proportional to volume.

Concept / Approach:
Percentage bulking is computed with respect to the saturated (no bulking) condition as the base: Bulking % = [(Vm - Vs) / Vs] * 100 = [(hm - hs) / hs] * 100, since depth is proportional to volume in the same container.

Step-by-Step Solution:
Compute difference in depths: hm - hs = 15 - 12 = 3 cm.Divide by saturated depth: 3 / 12 = 0.25.Convert to percent: 0.25 * 100 = 25%.Therefore, bulking of the moist sand = 25%.

Verification / Alternative check:
Typical bulking curves show maxima around 20–35% at about 4–6% moisture content for fine sand, aligning well with the computed 25%.

Why Other Options Are Wrong:

• 10%, 12%, 15%, 20% are lower than the correct calculation based on the given measurements.

Common Pitfalls:
Using moist volume directly for batching without bulking correction; always base volumetric batching on saturated-surface-dry or adjust volume by the measured bulking percentage.

Final Answer:
25%