Florida DOT Concrete Batchman/Operator Practice Exam

Which of the following is true about the mixing of concrete at high temperatures?

1. It may improve workability

2. It does not require changes to mixing times

3. It requires pre-mixing of aggregates and water

4. It is not affected by temperature

The correct answer is: It requires pre-mixing of aggregates and water

The mixing of concrete at high temperatures indeed requires pre-mixing of aggregates and water. At elevated temperatures, the rate of hydration increases, which can lead to a rapid loss of workability and an increased risk of issues like thermal cracking. Pre-mixing aggregates with water can help control the temperature of the materials and maintain consistent moisture content, ensuring that the concrete remains workable throughout the mixing process. In high-temperature conditions, it's essential to monitor and adjust the mixing process to ensure the integrity of the concrete is maintained. Pre-mixing also contributes to the uniform distribution of water within the aggregate, allowing for a more consistent mix as temperatures rise. Thus, this choice highlights a critical practice that helps manage the impacts of high temperature on concrete mixing effectively.