Florida DOT Concrete Batchman/Operator Practice Exam

Which of the following is NOT a benefit of using a HRWR concrete mix?

1. High strength

2. High slump

3. Increased setting time

4. Low water to cementitious materials ratio

The correct answer is: Increased setting time

Using a High-Range Water Reducer (HRWR) in a concrete mix enhances several properties of the final product, but it does not inherently increase the setting time of the concrete. HRWRs are specifically designed to maintain the workability of the mix while reducing the amount of water needed, which creates a low water-to-cementitious materials ratio. This results in higher strength concrete and can allow for higher slump levels, making the concrete easier to work with during placement. The setting time of concrete is influenced by various factors including temperature, relative humidity, and the specific formulation of the mix, but an HRWR does not typically prolong the initial setting time—the intention of using one is to improve workability without compromising strength or leading to excessively long times for setting and hardening. Therefore, stating that increased setting time is a benefit of using an HRWR concrete mix is inaccurate.