Question

In cement, generally the increase in strength during a period of 14 days to 28 days is primarily due to

• A. C3A
• B. C2S
• C. C3S
• D. C4AF

Answer 1

The Correct Option is C

In cement chemistry, the strength gain of cement over time is attributed to the hydration of its various mineral components. The most influential of these components are:

• C3A (tricalcium aluminate): It reacts quickly with water and contributes to the early strength development and heat evolution. However, it does not significantly contribute to strength gain after the initial set.
• C2S (dicalcium silicate): It hydrates and hardens slowly and contributes to the strength at later stages, particularly beyond 28 days.
• C3S (tricalcium silicate): It rapidly reacts with water and is primarily responsible for early strength development in cement. Specifically, C3S is highly responsible for strength gain from 14 days to 28 days.
• C4AF (tetracalcium aluminoferrite): It has minimal contribution to the strength of cement but is involved in the reduction of energy required during the manufacturing process.

The correct answer is therefore C3S. The increase in strength of cement from 14 to 28 days is primarily due to the continued hydration of C3S, which contributes significantly to the strength of the cement during this period.