Difficulty: Easy
Correct Answer: Increases workability at the same water content (improves cohesion and finishability)
Explanation:
Introduction / Context:
Air-entraining agents create microscopic, stable bubbles that enhance workability and provide freeze–thaw protection. Recognizing the primary effects helps balance durability and strength during mix design.
Given Data / Assumptions:
Concept / Approach:
Entrained air improves workability and cohesion by acting like microscopic ball bearings, allowing reduction in mixing water for the same slump if desired. It improves resistance to weathering by providing pressure-relief voids during freezing. However, compressive strength usually decreases slightly at the same w/c due to the added voids.
Step-by-Step Solution:
Verification / Alternative check:
Mix design guides quantify strength reduction per percent of entrained air and recommend air contents by exposure class.
Why Other Options Are Wrong:
Common Pitfalls:
Final Answer:
Increases workability at the same water content (improves cohesion and finishability).
Discussion & Comments