What should be the diameter and length specifications for the tamping rod in this test method?

The correct specification for the tamping rod in this test method is centered around the diameter and length that ensure proper compaction of the material being tested. The command for the tamping rod to have a diameter of 16 mm provides a sturdy yet manageable size that fits well within the confines of the measuring bowl, allowing for effective driving action without damaging the bowl or affecting the results. The stipulation for the overall length to be at least 4 inches greater than the measuring bowl depth ensures that the rod can reach the bottom of the bowl with sufficient length to allow for multiple tamps.

This design promotes efficiency in achieving uniformity in the compaction process, resulting in accurate and reproducible test results. The dimensional specifications ultimately support best practices in material testing, ensuring that the tamping rod is both effective and appropriate for the task at hand.

Other options may provide diameters or lengths that either fall short of these requirements or do not align with the necessary measurements for effective use in compaction processes, thus highlighting why the correct specification is essential.