Air-entrained cement/concrete — combined effects on properties Concrete made with an air-entrained cement generally:

Introduction / Context:
Air entrainment intentionally creates a system of tiny, well-dispersed bubbles. These voids improve durability in freezing conditions and enhance workability, with a modest sacrifice in compressive strength at equal w/c.

Given Data / Assumptions:

• Air contents typically 4–6% for moderate exposure.
• Mixes compared at equal cement and w/c ratio.
• Normal aggregates and curing conditions.

Concept / Approach:

Microscopic “ball bearing” action improves plasticity and cohesion, reducing segregation and bleeding. Entrained air provides pressure-relief pockets during freezing, increasing weathering resistance. However, the added voids reduce net load-bearing area, so strength at the same w/c is somewhat lower (often by about 10–15%).

Step-by-Step Solution:

Verification / Alternative check:

Design guides include strength adjustment factors per percent entrained air and prescribe target air contents by exposure zone.

Why Other Options Are Wrong:

• Each individual effect occurs; the comprehensive choice is therefore correct.

Common Pitfalls:

• Confusing entrained air with harmful entrapped air due to poor compaction.

Final Answer:

All of the above.