Building materials—mortar composition: In a standard cement mortar used for masonry, which ingredient acts as the binding material that holds the sand particles together after hydration?

Introduction / Context:

Masonry mortars are mixtures that bond bricks or stones into a unified structure. Their performance depends on the binder, the fine aggregate, and water (plus optional admixtures). Identifying which component is the true ‘‘binder’’ is critical for proportioning, strength, and durability expectations.

Given Data / Assumptions:

• Common cement mortars for brick/block masonry.
• Mortar components: cement (binder), sand (fine aggregate), water (activates hydration), optional pozzolans or fillers.
• Surkhi/cinder may be used as partial replacements or additives.

Concept / Approach:

Cement is the binding material. Upon hydration, cement forms calcium silicate hydrates (C–S–H) and other products that glue sand grains and masonry units together, creating strength and durability. Sand provides bulk and reduces shrinkage but does not bind; surkhi (burnt clay powder) can act as a pozzolanic additive with lime or cement but is not the primary binder in cement mortar. Cinder is a lightweight filler in some mixes, not the binder.

Step-by-Step Solution:

Verification / Alternative check:

IS/ASTM standards for mortar proportions describe cement as the hydraulic binder; strength classes are determined largely by cement content and type.

Why Other Options Are Wrong:

• Sand: inert aggregate; improves workability and stability.
• Surkhi: supplementary material; improves certain properties but not the principal binder here.
• Cinder: filler; not a binder.
• Waterglass: not a standard binder in cement mortar.

Common Pitfalls:

• Confusing lime mortar (binder = lime) with cement mortar (binder = cement).
• Overusing surkhi without adjusting cement and water demand.

Final Answer:

cement