Minimising shrinkage in concrete — effective mix and material strategies Which combination of actions can help reduce drying and autogenous shrinkage in concrete mixes for improved crack control and durability?

Introduction / Context:
Shrinkage in concrete arises from moisture loss (drying shrinkage) and internal self-desiccation (autogenous shrinkage), leading to cracking, curling, and durability issues. Proper mix design and material handling can significantly mitigate these risks without excessive reliance on post-crack remedies.

Given Data / Assumptions:

• Normal ambient curing conditions.
• Good construction practices and curing are applied.
• Focus on mixture-level strategies.

Concept / Approach:
Lowering the water–cement (w/c) ratio reduces capillary porosity and total water available for drying, thereby reducing shrinkage potential and improving strength. Optimizing paste content (reducing excess cement and water) limits the volume of shrinkage-prone phase. Well-graded aggregates improve packing and reduce paste demand, further curbing shrinkage. Bringing coarse and fine aggregates to saturated surface-dry (SSD) condition reduces early water absorption from paste, stabilizing the effective w/c ratio and mitigating plastic shrinkage. Together, these actions synergistically reduce shrinkage.

Step-by-Step Solution:

Verification / Alternative check:
Laboratory tests show linear correlations between paste volume and drying shrinkage; field experience corroborates that optimized grading and SSD aggregates improve dimensional stability.

Why Other Options Are Wrong:

• Choosing any single measure yields partial benefit; the combined approach is most effective.

Common Pitfalls:
Chasing workability solely by adding water; neglecting curing; using overly rich pastes that elevate shrinkage risk.

Final Answer:
All the above