Volumetric stability of ordinary cement concrete: after casting and subsequent drying, how does ordinary concrete generally behave volumetrically?

Introduction / Context:
Dimensional stability of hardened concrete is crucial for crack control and serviceability. Drying shrinkage is a common phenomenon that can lead to cracking if joints, reinforcement, and curing are not properly designed.

Given Data / Assumptions:

• Ordinary Portland cement concrete, normal ambient drying.
• No expansive additives or shrinkage-compensating cement.
• Typical water–cement ratios and aggregate types.

Concept / Approach:
After hydration and initial set, concrete loses moisture to the environment. As capillary water evaporates and internal RH drops, the cement paste experiences shrinkage. Aggregate restrains paste shrinkage to some extent, but net behavior is drying shrinkage (volume reduction).

Step-by-Step Solution:
Observe common field behavior: slabs-on-ground crack without joints due to shrinkage.Understand mechanism: moisture loss and microstructural changes cause volume reduction.Therefore, ordinary concrete on drying → shrinks.

Verification / Alternative check:
Standards specify shrinkage tests; admixtures and SCMs can mitigate but not reverse basic trend.

Why Other Options Are Wrong:

• Expands: occurs with expansive cement or alkali–silica reactions, not the general case.
• Mix: not a valid behavioral description.
• None of these / Swells then stabilizes: not representative of ordinary OPC concrete drying.

Common Pitfalls:
Confusing early thermal expansion (heat of hydration) with long-term drying shrinkage; neglecting proper curing and jointing.

Final Answer:
Shrinks