Cement types: the high early strength of rapid hardening cement at initial stages is mainly due to which factor?

Introduction / Context:
Rapid hardening cement is a specialized type designed to gain strength faster than ordinary Portland cement (OPC). It is often used in road repairs, precast work, and cold-weather concreting.

Given Data / Assumptions:

• Rapid hardening cement must achieve high strength in 3 days equivalent to OPC's 7 days.
• We seek the main reason for early high strength.

Concept / Approach:
The fineness of cement greatly influences hydration rate. Finer grinding provides a larger surface area for chemical reaction with water, accelerating hydration of tricalcium silicate, the main strength-giving compound. Although burning temperature and lime/tricalcium content affect long-term properties, early strength gain is chiefly due to fine grinding.

Step-by-Step Solution:
Identify property: early strength gain.Match with factor: finer grinding increases surface area.Thus, answer: finer grinding.

Verification / Alternative check:
IS 269 commentary states rapid hardening cement is manufactured by grinding cement more finely and controlling composition.

Why Other Options Are Wrong:

• High burning: affects compound formation, not early strength directly.
• Increased lime content: influences long-term strength and soundness.
• Higher tricalcium silicate: contributes, but the decisive factor is fine grinding.

Common Pitfalls:

• Confusing chemical composition changes with physical fineness factor.

Final Answer:
finer grinding