ACI Concrete Field Testing Technician - Grade I Practice Exam

How much time is allowed for lifting the slump mold?

1. 3 ± 1 seconds

2. 5 ± 2 seconds

3. 8 ± 3 seconds

4. 10 ± 5 seconds

The correct answer is: 5 ± 2 seconds

The correct time allowed for lifting the slump mold is indeed 5 ± 2 seconds. This timeframe is critical to ensure consistency and reliability in the slump test results, which measures the workability or consistency of fresh concrete. Following the established protocol for this time allows for the correct measurement of the slump without causing disturbances to the concrete, which could skew the results. In the context of this test, lifting the mold too quickly can cause the concrete to rebound or slough off, leading to an inaccurate slump measurement. Similarly, a delay that exceeds the specified range might allow the concrete to settle or harden, again affecting the accuracy of the test. Thus, maintaining the 5 ± 2 seconds window is essential for gathering precise and standardized data reflecting the concrete's properties.