ACI Concrete Field Testing Technician - Grade I Practice Exam

When rodding each upper layer of concrete in a cylinder, how far should the tamping rod penetrate into the underlying layer?

1. 1/2 in. [13 mm]

2. 1 in. [25 mm]

3. 1 1/2 in. [38 mm]

4. 2 in. [50 mm]

The correct answer is: 1 in. [25 mm]

The correct approach for rodding the upper layer of concrete in a cylinder involves the tamping rod penetrating into the underlying layer by a depth of 1 inch (25 mm). This penetration ensures proper bonding and integration of the layers, which is essential for achieving a uniform and consistent sample. The reason for this specific depth is to avoid creating weak interfaces between layers, which could compromise the integrity of the sample and lead to inaccurate strength measurements during testing. By allowing the rod to penetrate by this specified depth, it helps to consolidate the upper layer effectively, ensuring that there are no significant air pockets or voids, and that the concrete is properly compacted throughout. This standard practice aligns with the guidelines set by organizations such as the American Concrete Institute (ACI), emphasizing the importance of maintaining consistency in testing procedures to obtain reliable and comparable results.