Modeling Compressive Strength Development in Florida Concrete

The Florida Department of Transportation (FDOT) specifications contain equations of concrete compressive strength to predict equivalent 28-day strengths based on core strengths at other times. The FDOT equations are many years old, and are not likely to represent current FDOT concrete mixes. Compressive strength testing at various ages, by using a typical FDOT concrete mix proportion, was performed in order to derive appropriate strength development models. Variation in the mixes was achieved through the substitution of cement types, slag for fly ash, and coarse aggregate type. Selected existing models from the literature were examined for statistical goodness-of-fit to the test data. The best performing models relating the 28-day compressive strength to strengths of concrete aged more than 42 day were recommended.