NASCLA General Contractor Practice Exam

Question: 1 / 400

What is the purpose of adding an air-entraining agent to concrete?

To increase strength

To prevent freeze-thaw damage

The purpose of adding an air-entraining agent to concrete is to prevent freeze-thaw damage. This type of additive creates tiny, stable air bubbles within the concrete mix, which acts as shock absorbers during freeze-thaw cycles. When water in the concrete freezes, it expands. The air bubbles provide space for this expansion, reducing internal pressure and the risk of cracking. This is crucial in climates where temperatures fluctuate frequently, as repeated freezing and thawing can lead to significant deterioration over time.

While the other options might relate to different aspects of concrete performance—such as workability, strength, or curing—air-entrainment specifically addresses the durability concerns associated with freeze-thaw cycles.

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To enhance curing

To improve workability

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