North Carolina General Contractors Practice Exam 2025 - Free Contractors Practice Questions and Study Guide.

A retarder is an additive used in concrete mixes to slow down the setting time of the concrete. By increasing the workability, a retarder allows for a longer period during which the concrete can be easily mixed, transported, placed, and finished without the material beginning to set. This extended working time can be particularly advantageous in hot weather conditions or when transporting concrete over long distances, as it helps to prevent premature hardening.

In summary, a retarder enhances the workability of concrete by providing additional time for laborers to manipulate the concrete, thereby improving the overall quality and finish of the work.