What do we need to do while designing an air-entrained concrete?

A. Water-cement ratio is to be reduced

B. Proportion of aggregates is to be reduced

C. An allowance for the entrained air is made

D. All options are correct

Correct Answer: D. All options are correct

💨 Designing Air-Entrained Concrete

Air entrainment introduces tiny, stable air bubbles (0.05–1.25 mm) into the concrete using a surface-active admixture. These bubbles improve resistance to freeze–thaw cycles and help workability. However, each 1% of entrained air reduces compressive strength by roughly 5%, so the mix must be adjusted in three ways:

A — Reduce the water–cement ratio to compensate for the strength loss caused by the air voids.

B — Reduce the proportion of aggregates because the air itself occupies volume in the paste, displacing some aggregate.

C — Make an allowance for the entrained air in the absolute-volume calculations during mix design.

All three adjustments are necessary — option D.

Key takeaway

Air entrainment is not free: lower w/c ratio + less aggregate + air allowance are the three standard corrections when designing air-entrained mixes.

← Back to MCQs on Concrete – Page 2