AASHTO R 39-19

This standard practice covers procedures for making and curing test specimens of concrete in the laboratory under accurate control of materials and test conditions.

The values stated in either inch-pound units or SI units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.