Properties of sand used in building construction: Which statements are correct?

Introduction / Context:
Sand is a ubiquitous fine aggregate in concrete and mortar and is also used as a capillary break under floors. Understanding its composition and hydraulic behavior helps in selecting appropriate site practices.

Given Data / Assumptions:

• Sand is predominantly silica (quartz) with grains produced by weathering and abrasion.
• Frost action refers to damage from freeze–thaw cycles.
• Capillary rise depends strongly on pore size; coarse, well-graded sand provides large pores and high permeability.

Concept / Approach:
(a) is a standard description: most natural sands are rich in silica from rock disintegration. (b) Quartz itself is stable during freezing; unlike porous stones or clays, individual grains do not suffer frost spalling. (c) Because sand has relatively large pore sizes and is permeable, it produces low capillary suction compared to silts/clays; a sand layer thus acts as a capillary break beneath floors and pavements, effectively preventing significant upward capillary rise.

Step-by-Step Solution:
Assess (a): true for common construction sands.Assess (b): quartz grains are inert to freeze–thaw → correct.Assess (c): coarse permeable sand interrupts capillary continuity → practically prevents capillary rise.Hence select “All of the above.”

Verification / Alternative check:
Soil mechanics shows capillary rise is inversely proportional to pore size; sands exhibit negligible capillary head compared to fines, supporting their use as capillary breaks.

Why Other Options Are Wrong:
Only (a) and (b) ignores the well-known capillary-break function of sand layers.

Common Pitfalls:
Using fine or silty sand that can still develop capillarity; not compacting the sand bed, allowing differential settlements.

Final Answer:
All of the above.