Fracture Energy of Concrete by Maturity Method

Abstract

The maturity method is a nondestructive testing technique for the estimation of in-place compressive strength of concrete during construction. It combines the effects of time and temperature into an index that is correlated against the in-place compressive strength. The basis for the maturity method is a hyperbolic model relating the gain in concrete strength to the intensity of strength development at a constant temperature. The study reported herein aims at development of a methodology for the application of the maturity method for the estimation of in-place fracture energy during construction of concrete structures. It investigates the validity and applicability of the hyperbolic model to fracture energy. Formulation of the hyperbolic model is based on the assumptions that the fracture energy is insensitive to curing temperatures; and the relationship between the fracture energy and the rate of fracture energy gain is linear. The validity of these assumptions is experimentally confirmed through standard fracture energy tests on beams. The experiments were performed for the first mode or opening mode of fracture. Fracture energy gain data for concrete beams cured at 57.2, 73.4, and 95 °F (14, 23, and 35 °C) were obtained at six different ages ranging nominally from I day to later ages. Results presented herein are encouraging as they confirm the applicability of the hyperbolic relationship in terms of fracture energy gain and, therefore, lead to a nondestructive method for applications during construction. Due to the range of the curing temperatures investigated here, the applicability of the methodologies presented is limited to the temperature ranges of 57.2 to 95 °F (14 to 35 °C).