General Contractor Practice Exam

What does air entrainment in concrete prevent?

1. Scaling

2. Crumbling

3. Cracking

4. Settlement

The correct answer is: Scaling

Air entrainment in concrete is a process that involves the intentional incorporation of tiny air bubbles into the concrete mix. This practice is crucial, especially in regions that experience freeze-thaw cycles. The primary function of these air bubbles is to provide space for water to expand when it freezes, thereby preventing cracks and damage to the concrete. When water freezes, it expands, and if there is no space for this expansion, the pressure can cause the surface of the concrete to flake or scale off, leading to aesthetic and structural issues. Therefore, air entrainment effectively reduces the risk of scaling, which is particularly important in outdoor concrete that is exposed to harsh weather conditions. While air entrainment does provide some benefits in terms of reducing crumbling and cracking, its most significant role is in preventing scaling, especially on surfaces subject to moisture and freeze-thaw cycles. Likewise, while settlement is related to the compaction of concrete, air entrainment does not directly address this issue. Thus, the primary advantage of air-entrained concrete is its protective role against scaling.