Micromechanical Analyses for Measurement and Prediction of Hot-Mix Asphalt Fracture Energy

Abstract

A verification of fracture energy density is presented as a fundamental fracture threshold in hot-mix asphalt. Fracture energy density was evaluated with the semicircular bending (SCB) test. Experimental analyses were enhanced by a digital image correlation system capable of providing a dense and accurate displacement–strain field of composite materials at the microstructural level and suitable for describing the cracking behavior of materials at crack initiation. The resulting fracture behavior in the SCB was predicted with a displacement discontinuity method to explicitly model the microstructure of asphalt mixtures and to predict their fracture energy density. The input parameters for the displacement discontinuity micromechanical model of the SCB were obtained from the Superpave® indirect tensile test. The predicted crack initiation and crack propagation patterns are consistent with observed cracking behavior. The results also imply that fracture in mixtures can be modeled effectively with a micromechanical approach that allows for crack growth both along aggregate surfaces and through aggregates. Finally, the results presented lead to the promising statement that fracture energy density for mixtures is a fundamental fracture threshold and can be both consistently measured and predicted for different laboratory test configurations.