ACI Concrete Field Testing Technician - Grade I Practice Exam

What is the approximate depth of concrete after placing the first layer of the slump test?

1. 2 in. [50 mm]

2. 2 5/8 in. [70 mm]

3. 3 in. [75 mm]

4. 4 in. [100 mm]

The correct answer is: 2 5/8 in. [70 mm]

The depth of concrete after placing the first layer of the slump test is approximately 2 5/8 inches (70 mm). This depth is critical because the slump test involves filling a slump cone in three equal layers, with each layer being tamped down a specific number of times (usually 25 taps for the first two layers and 10 taps for the final layer) to achieve proper compaction. The first layer is filled to the correct depth of 2 5/8 inches, which ensures that the volume of concrete being tested is consistent and that the results of the slump test accurately reflect the workability of the concrete mix. This specific measurement aligns with the guidelines outlined in ASTM C143, which governs the procedures for conducting the slump test. By starting with this precise depth, technicians ensure uniformity in testing, leading to reliable and comparable results.