When cement is first produced, its mechanical properties are time-dependent and involve hydration. The hydration process is a thermally-activated reaction that can be described by the Arrhenius equation. Predictions of the mechanical properties of concrete, particularly compressive strength, are based on maturity indexes. This article presents a simple and efficient procedure to evaluate the activation energy and the rate constant of concrete. The authors contend that these two parameters can be used for a rapid prediction of the mechanical properties of concrete and particularly the evolution of compressive strength. They also allow the separation of effects due to physical phenomena such as humidity loss. The procedure uses an experimentally-determined parameter called “hardening time” as an indicator of equivalent maturity when comparing two hardening profiles. The authors provide the test results from specimens of six concrete types; results validate the proposed procedure. The methodology allows a fast and accurate prediction of compressive strength on site; 72 hours are sufficient to gather the data and provide accuracy of less than 8% error. The resulting improvements in understanding of compressive strength evolution can lead to savings during construction and improved safety.