Bulking of Sand – Identify the Incorrect Statement About Moisture Effects on Volume With reference to bulking behavior of fine aggregates, which one of the following statements is NOT correct under typical field conditions?

Introduction:
Bulking refers to the temporary increase in the apparent volume of sand at low moisture contents because thin water films create surface tension forces that separate particles. Understanding this effect is crucial in volumetric batching of mortar and concrete to avoid under-sanded mixes and strength loss.

Given Data / Assumptions:

• Fine sand shows greater bulking than coarse sand at the same moisture content.
• Peak bulking typically occurs around 4%–6% moisture by weight.
• At saturation, bulking disappears because water floods voids and eliminates the capillary tension effect.

Concept / Approach:

At low moisture, a meniscus forms between grains, increasing apparent volume. As moisture increases beyond the peak, the meniscus effect is lost and the volume contracts back toward the dry volume. Therefore, any statement implying increasing bulking at higher moisture (toward saturation) is incorrect.

Step-by-Step Solution:

Verification / Alternative check:

Site tests (e.g., bulking jar test) and standard texts show maximum bulking of fine sands may be in the 20%–35% range near 4%–6% moisture and reduce to ~0% at full saturation.

Why Other Options Are Wrong:

They are not wrong: (a) states a commonly observed range; (b) notes fine sand bulks more; (d) correctly states saturation removes bulking; (e) accurately explains the surface tension mechanism.

Common Pitfalls:

Assuming constant bulking increase with moisture; ignoring that volumetric batching must be corrected for bulking to avoid lean mixes.

Final Answer:

If moisture content exceeds about 10%, bulking begins to increase again and becomes greater at full saturation