Red Seal Concrete Finisher Practice Exam

Name a common type of admixture used to accelerate concrete setting.

1. Silica fume

2. Calcium chloride

3. Lime

4. Fly ash

The correct answer is: Calcium chloride

Calcium chloride is recognized as a common type of admixture specifically used to accelerate the setting time of concrete. Its primary function is to promote the hydration process of cement, facilitating quicker hardening and setting. This is particularly beneficial in cold weather conditions, where the curing process can be slowed down significantly. When added to concrete mixes, calcium chloride increases the rate of cement hydration, allowing concrete to achieve its strength more quickly and reducing the time needed for forms to be stripped and for subsequent construction activities to proceed. This property helps ensure that projects remain on schedule, particularly in situations where time constraints are critical. Other choices serve different purposes in concrete mixtures. For example, silica fume is primarily used to enhance the strength and durability of concrete, while lime is often associated with improving workability and reducing shrinkage. Fly ash is typically utilized as a partial replacement for cement to improve workability and durability but does not accelerate setting. Thus, calcium chloride stands out as the clear choice for accelerating the setting process.