Rapid Hardening Cement – Reason for Early Strength Gain Rapid hardening cement develops higher early strength compared to ordinary Portland cement primarily because of which factor?

Introduction:
Rapid hardening cement (RHC) is selected where early formwork removal or quick strength development is required, such as in precast yards or cold weather concreting with time constraints. Understanding why RHC gains early strength helps engineers choose appropriate cement for project needs.

Given Data / Assumptions:

• RHC is chemically similar to OPC but optimized for early hydration.
• Early strength correlates strongly with C3S content and particle fineness.
• Final 28-day strengths can be comparable to OPC for properly cured mixes.

Concept / Approach:

Increasing C3S accelerates formation of C-S-H gel at early ages. Finer grinding increases surface area, raising hydration rate and early heat evolution. Together, these factors yield higher early strengths without relying on excessive gypsum or solely on aluminates.

Step-by-Step Solution:

Verification / Alternative check:

Standards and manufacturer datasheets show higher early strength and fineness values for RHC versus OPC, consistent with the mechanism above.

Why Other Options Are Wrong:

Lower lime/coarser grinding reduces early strength; extra gypsum risks flash set; aluminates affect set/heat more than sustained early strength; pozzolana alone is not the basis of rapid-hardening behavior.

Common Pitfalls:

Confusing rapid hardening cement with rapid setting formulations; assuming gypsum increase alone ensures early strength.

Final Answer:

Higher tricalcium silicate (C3S) content and much finer grinding than OPC