What diameter must the tamping rod be according to the specifications?

The specifications for the tamping rod emphasize the importance of its diameter for ensuring consistency in testing, particularly in procedures such as concrete testing for workability. The correct choice, which indicates a diameter of 5/8 inch +/- 1/16 inch, is specified to allow for enough strength and stiffness in the rod while also fitting well with the sample sizes used during tests. This dimension is a standard reference in various concrete testing methods, facilitating uniformity in practices across different laboratories.

The choice incorporates a tolerance of +/- 1/16 inch, which is important as it accounts for slight manufacturing variances, ensuring that even with small differences, the rod remains suitable for effective use in testing. This blend of precision and flexibility in specifications helps maintain the integrity of test results, making it critical that the correct diameter aligns with established guidelines. Other options do not adhere to these specifications, thus failing to provide the required performance for the tests.