Thermal expansion of concrete — effect of aggregate type How does the coefficient of thermal expansion (CTE) of concrete vary with the predominant aggregate type?

Introduction / Context:
The thermal movement of concrete is dominated by the aggregate, which makes up most of the volume. Selecting aggregates with lower coefficients of thermal expansion can help reduce thermal stresses and joint movements in pavements and large structures.

Given Data / Assumptions:

• Normal-weight concrete with a single predominant aggregate type.
• Similar paste content, curing, and moisture conditions.
• Comparative, qualitative statements about CTE.

Concept / Approach:

Siliceous aggregates (rich in quartz) have relatively high thermal expansion, raising the composite concrete CTE. Granitic/igneous aggregates are generally in the intermediate range. Carbonate (limestone/dolomite) aggregates typically have lower thermal expansion, leading to lower concrete CTE. Thus, the ranking is siliceous > igneous ≈ intermediate > limestone for CTE magnitude.

Step-by-Step Solution:

Verification / Alternative check:

Pavement design manuals account for aggregate-dependent CTE when estimating joint spacings and thermal stresses.

Why Other Options Are Wrong:

• “None of the above” conflicts with well-established material data.
• Picking only one statement misses the complete comparative picture.

Common Pitfalls:

• Neglecting moisture state effects; apparent CTE can vary with saturation.

Final Answer:

All of the above.