ACI Concrete Field Testing Technician - Grade I Practice Exam

For cylinders with a diameter of 6 in. [150 mm] or greater, the tamping rod must have a diameter of what?

1. 1/2 in. [13 mm]

2. 3/4 in. [19 mm]

3. 5/8 in. ± 1/16 in. [16 mm ± 2 mm]

4. 1 in. [25 mm]

The correct answer is: 5/8 in. ± 1/16 in. [16 mm ± 2 mm]

The correct answer indicates that for concrete cylinders with a diameter of 6 inches (150 mm) or greater, the tamping rod must have a diameter of 5/8 inch ± 1/16 inch (16 mm ± 2 mm). This specification is crucial as it relates to the compaction process during concrete sampling to ensure consistent results in testing. The rationale behind this specification is rooted in the need to efficiently consolidate the concrete mix within the cylinder without over- or under-compacting it. The size of the tamping rod is designed to effectively compact the concrete while minimizing air voids and ensuring the concrete is homogeneous within the sample. The chosen diameter provides adequate density without interfering with the integrity of the cylinder walls, ultimately leading to reliable test results when assessing the strength and quality of the concrete. By establishing a precise tamping rod diameter, standards help align the procedures followed by field technicians with those outlined in ASTM and ACI guidelines, reinforcing quality control in concrete testing across varying projects.