Florida DOT Concrete Batchman/Operator Practice Exam

For concrete containing a water-reducing retarding admixture, what is the maximum time for depositing the concrete in an agitator truck?

1. 60 minutes

2. 90 minutes

3. 120 minutes

4. 150 minutes

The correct answer is: 90 minutes

The maximum time for depositing concrete containing a water-reducing retarding admixture in an agitator truck is 90 minutes. This time limit is crucial for maintaining the quality and performance of the concrete mix. Water-reducing retarding admixtures are designed to slow down the setting time of the concrete, which can be beneficial in hot weather conditions or when longer transport times are expected. However, exceeding the 90-minute mark could jeopardize the mix's workability and lead to issues such as premature setting, which can affect the strength and durability of the finished product. By adhering to this time frame, operators can ensure that the concrete remains workable and that its properties are preserved until it reaches the pour site. This time limit is established based on industry standards and practices to guarantee that the concrete performs as intended. Thus, it is essential for batch operators and concrete producers to be aware of these specifications to avoid potential issues during placement.