Florida DOT Concrete Batchman/Operator Practice Exam

What effect does entrained air have on concrete's strength?

1. Slightly increase

2. Slightly reduce

3. No effect

4. Significantly reduce

The correct answer is: Slightly reduce

Entrained air in concrete is intentionally introduced to improve its workability and resistance to freeze-thaw cycles. While it enhances the durability of concrete under certain conditions, it does have the effect of slightly reducing the strength of the concrete. The presence of entrained air creates small voids within the concrete mix. These voids occupy space that would otherwise be filled with solid material, resulting in a reduction in the overall density and strength of the concrete. Although the reduction in strength is usually slight, it is an important consideration in applications where strength is critical. In general, the trade-off involves improving the concrete's performance in terms of durability and resistance to cracking, particularly in environments subject to cycles of freezing and thawing, while accepting a minor reduction in compressive strength. This characteristic is well recognized in concrete design and materials science, underpinning the rationale for using air-entraining agents in specific applications.