ACI Concrete Field Testing Technician - Grade I Practice Exam

What is the specified number of strokes required when rodding each layer of concrete?

1. 15 strokes

2. 20 strokes

3. 25 strokes

4. 30 strokes

The correct answer is: 25 strokes

When conducting a concrete slump test, the procedure for consolidating each layer of concrete involves a specific number of strokes with a rod. The correct answer, which is 25 strokes, is based on the standardized testing method outlined by ASTM C143, which governs the slump test of hydraulic cement concrete. In this procedure, the required number of strokes ensures that each layer of concrete is adequately consolidated to provide a representative and reliable measure of the material’s workability. Rodding the concrete sufficiently minimizes voids and air pockets, which can affect the test's accuracy. Adequate consolidation also helps to ensure uniformity within the test sample, leading to better consistency in results. The chosen number of strokes plays a critical role in achieving the correct density and consistency required for accurate readings. This thoroughness is essential for producing valid test results that represent the concrete's characteristics and performance.