This standard provides procedures for estimating the early concrete strength for pavement opening only through the use of a maturity index. For other uses of maturity for concrete strength estimation use T 276, T 325, or both. This standard requires determination of the strength–maturity relationship of the approved concrete job mix and determination of the temperature history subsequent to placement in the field. The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the inch-pound units are shown in parentheses. 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.