Florida DOT Concrete Batchman/Operator Practice Exam

Which aspect of concrete does air-entraining admixture NOT improve?

1. Durability

2. Workability

3. Setting speed

4. Freeze-thaw resistance

The correct answer is: Setting speed

Air-entraining admixtures are designed to introduce microscopic air bubbles into the concrete mixture. These air bubbles help improve various properties of concrete, particularly its durability and freeze-thaw resistance. The inclusion of air bubbles enhances the concrete's workability, making it easier to mix, handle, and place. This is particularly beneficial in reducing the potential for segregation and bleeding. However, it is important to note that air-entraining admixtures do not significantly affect the setting speed of concrete. The setting speed is primarily influenced by the cement type, water-cement ratio, temperature, and other chemical accelerators or retarders, rather than the introduction of air bubbles. Therefore, while air-entraining admixture contributes positively to many aspects of concrete performance, it does not play a role in improving the setting speed.