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Published: 2004

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Performance modeling of asphalt concrete pavements is one of the most difficult, but important tasks facing pavement engineers. Experiences at North Carolina State University suggest that this task is best accomplished by utilizing two separate models; one to account for the material behavior and another to account for boundary conditions, such as tire-pavement interaction, temperature gradient along the layer thickness, pavement structural design, etc. The material characterization model should focus on the material irrespective of geometry, i.e., fundamental properties. The structural model should be robust enough to account for the range of conditions experienced by pavements in service. Two peer-reviewed and published papers are presented here which deal with the development of a constitutive material model for asphalt concrete. In the first, the viscoelastoplastic continuum damage model in tension is applied to materials from the Federal Highway Administration's Accelerated Load Facility study on modified mixture performance. It is shown that the material model is capable of describing the behavior of the tested mixtures over a range of conditions from primarily viscoelastic to primarily viscoplastic. Further, the model shows sensitivity to changes in asphalt binder and the ability to predict the behavior of asphalt concrete mixtures containing polymer modified binder. The second paper presents results from an experimental study of anisotropy in asphalt concrete. Anisotropy occurs due to the preferential orientation of aggregate particles in the mixture and is found to have varying levels of significance depending on both the mode of loading and the levels of deformation applied. In the linear viscoelastic range, anisotropy is found to have little effect on the material behavior, whereas under monotonic compressive loading until failure, it is found to contribute significantly. Further, it is found that temperature and rate affect the significance of anisotropy.