This test method covers a procedure for making and curing concrete specimens and for testing them at an early age. The specimens are stored under standard curing conditions and the measured temperature history is used to compute a maturity index that is related to strength gain. This test method also covers a procedure for using the results of early-age compressive-strength tests to project the potential strength of concrete at later ages. The values stated in SI units or inch-pound 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.