What does an air-entraining admixture do?

What does an air-entraining admixture do?

• A. It creates microscopic air bubbles in concrete, improving workability, resistance to freezing and thawing, and durability.
• B. It accelerates curing by releasing moisture.
• C. It increases the water demand to improve compaction.
• D. It chemically bonds with cement to strength the matrix.

Answer: (A)

Air-entraining admixture creates microscopic, evenly distributed air bubbles in concrete. These tiny bubbles form a stable air-void system that provides space for water to expand when it freezes, which reduces internal pressure, lowers the risk of cracking and spalling, and thus enhances durability in freeze–thaw environments. The small air voids also help improve workability, making placement and finishing easier because they act like tiny lubricants within the paste. They do not accelerate curing by releasing moisture, they do not increase water demand for compaction, and they do not chemically bond with cement to strengthen the matrix.

Air-entraining admixture creates microscopic, evenly distributed air bubbles in concrete. These tiny bubbles form a stable air-void system that provides space for water to expand when it freezes, which reduces internal pressure, lowers the risk of cracking and spalling, and thus enhances durability in freeze–thaw environments. The small air voids also help improve workability, making placement and finishing easier because they act like tiny lubricants within the paste. They do not accelerate curing by releasing moisture, they do not increase water demand for compaction, and they do not chemically bond with cement to strengthen the matrix.