North Carolina Building Contractor License Practice Exam

Which type of concrete is highly resistant to freeze and thaw cycles?

1. Air-entrained concrete

2. High-strength concrete

3. Lightweight concrete

4. Reinforced concrete

The correct answer is: Air-entrained concrete

Air-entrained concrete is specifically formulated to improve its resistance to freeze and thaw cycles. This type of concrete contains tiny air bubbles that are deliberately introduced into the mix through the use of air-entraining agents. These microscopic air pockets allow for the expansion of water when it freezes, thereby minimizing the internal pressure that could otherwise cause cracking and damage to the concrete structure during freeze-thaw cycles. The presence of these air voids effectively enhances the durability and longevity of the concrete in environments that experience these temperature fluctuations. Other types of concrete, such as high-strength concrete, lightweight concrete, and reinforced concrete, do not inherently possess the air-entraining properties that contribute to resilience against freeze-thaw damage. High-strength concrete focuses on achieving elevated compressive strength rather than freeze resistance. Lightweight concrete is designed for reduced density and weight but does not specifically target freeze-thaw performance. Reinforced concrete improves tensile strength and structural integrity through the inclusion of reinforcement materials but does not address freeze-thaw durability unless combined with air-entraining additives. Therefore, air-entrained concrete stands out as the most effective option for preventing damage from freeze-thaw cycles.