Concrete Strength Gain – primary cause Concrete gains strength primarily due to which process during and after setting?

Introduction / Context:
Understanding the fundamental mechanism of strength gain is essential for correct curing, mix design, and troubleshooting. Many misconceptions persist at site about drying and “hardening,” so it is vital to distinguish hydration from evaporation or reactions with aggregate.

Given Data / Assumptions:

• Ordinary Portland cement-based concrete.
• Inert mineral aggregates (sand and stone) that do not chemically bond in a primary sense.
• Normal moist curing unless otherwise stated.

Concept / Approach:

Strength develops because cement hydrates—cement compounds react with water to form binding products such as calcium silicate hydrates that glue the aggregate skeleton together. Aggregates provide volume stability and stiffness but do not chemically drive strength in normal concrete. Evaporation of water merely reduces available water; excessive drying prematurely halts hydration, harming strength rather than creating it.

Step-by-Step Solution:

Verification / Alternative check:

Standard texts and laboratory practice show continued strength gain when moisture is maintained, confirming hydration as the key process.

Why Other Options Are Wrong:

Options A and B misattribute the mechanism; option D cannot be correct because A and B are incorrect.

Common Pitfalls:

Mistaking surface drying for strength development; neglecting curing which sustains hydration and ensures design strength.

Final Answer:

Hydration of cement