Florida DOT Concrete Batchman/Operator Practice Exam

What is the maximum allowable time for depositing concrete in place for agitating trucks without water reducers or retarders?

1. 30 minutes

2. 45 minutes

3. 60 minutes

4. 90 minutes

The correct answer is: 60 minutes

The maximum allowable time for depositing concrete in place for agitating trucks, when water reducers or retarders are not used, is set to ensure that the concrete maintains its workability and doesn't begin to set before it can be placed. When concrete is agitated in a truck, the mixing action helps keep the ingredients in suspension, but there is a limit to how long the concrete can remain in this state. Typically, the time limit is established based on the properties of the concrete mix and the environmental conditions. In this case, the 60-minute limit for depositing concrete strikes a balance between allowing sufficient transportation time and preventing premature setting that could compromise the quality and integrity of the concrete. Exceeding this timeframe can lead to issues such as reduced workability, difficulty in placing the concrete, and inconsistent set times. Factors like temperature, humidity, and the specific characteristics of the concrete mix play a pivotal role in determining these limits; however, the 60-minute time frame serves as a standard guideline to ensure that the concrete can be placed effectively and meet performance expectations.