Laboratory testing suite for characterization of asphalt concrete mixtures obtained from field cores
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The calibration of pavement models to field observations can be an important step in refining the model to accurately predict the pavement response. A major challenge with model calibration has been obtaining the material properties with laboratory test geometries that have the capability to use specimens fabricated from standard field cores. Unless complicated fabrication procedures are used, field cores limit the specimen geometry to cylindrical shapes and thin cross sections due to the relatively thin pavement lifts typically used during pavement construction. Recent developments in fracture testing of HMA concrete have enabled the development of a testing suite that captures both continuum and material separation properties from field cores. The testing suite utilizes two specimen geometries (indirect tension and disk-shaped compact tension) and was developed to investigate reflective cracking mechanisms. The main objective of this paper is to illustrate the application of the testing suite to provide material properties for material constitutive models. For this purpose, a single pavement with three test sections was selected. The test sections consist of similar pavement structures, but different asphalt mixture designs, namely different grades of asphalt binder. The testing suite was successful in determining the continuum properties of interest, namely complex modulus, creep compliance, and coefficient of thermal expansion, using the indirect tension geometry. Two parameters were required to describe the material separation. The tensile strength was obtained using the indirect tension geometry while the fracture energy was determined using the disk-shaped compact tension geometry. As expected, the continuum properties are influenced by the asphalt binder grade where both the complex modulus and creep compliance show the same trends. The material separation properties also appear to be influenced by the asphalt binder grade. The fracture energy appears to distinguish the fracture resistance of the material better than the tensile strength. Future work includes integrating the material properties with finite element analysis to provide a detailed analysis of the pavement structure to determine the mechanisms that initiate the reflective cracks.