North Carolina Building Contractor License Practice Exam

What percentage of fly ash is a requirement for concrete subject to Exposure Class F3?

1. 25%

2. 50%

3. 10%

4. 30%

The correct answer is: 25%

For concrete that is subject to Exposure Class F3, which deals with exposure to sulfate environments, the requirement for fly ash is set at a minimum of 25%. The incorporation of fly ash in concrete can improve workability and durability, particularly in sulfatic environments, as it helps mitigate the effects of sulfate attacks on concrete. In North Carolina, standards for concrete and the use of supplementary cementitious materials like fly ash are outlined in building codes to ensure the long-term performance of concrete structures. Therefore, the 25% requirement aligns with the regulations set forth for achieving the appropriate resistance to such aggressive environmental factors.