Why is the bulking of sand test performed?
- ATo determine the density of sand.
- BTo measure the increase in sand volume due to moisture content.Correct
- CTo calculate the silt content in sand.
- DTo assess the specific gravity of sand.
Solution
Concept
Bulking is the phenomenon where the volume of a given mass of moist sand increases compared to dry sand due to moisture films causing surface tension forces.
Step-by-step solution
1. Understand that moisture creates a film around sand grains, causing surface tension and separating the particles. 2. This results in an increase in volume (bulking) for the same dry weight of sand. 3. The bulking of sand test quantifies this volume increase so that mix proportions (which are typically done by volume) can be appropriately corrected.
Explanation
The bulking of sand test is performed to measure the increase in the volume of fine aggregate (sand) caused by the presence of moisture. Moisture forms a thin water film around sand particles, causing them to push apart due to surface tension, which significantly increases the apparent volume.
Why the other options are wrong
A: Density of sand is determined using density-related tests, not bulking. C: Silt content is measured by the sedimentation or field silt test. D: Specific gravity of sand is determined using a pycnometer.
Shortcut
Remember: Moisture in sand pushes particles apart -> volume increases (bulking).
Common mistake
Confusing bulking of sand with silt content test or density determination.
Correct answer: B) To measure the increase in sand volume due to moisture content.