Asphalt Materials Analysis Group (AMAG)
The main research focus of AMAG is modeling the behavior of asphalt and asphalt concrete. The approach that AMAG takes is one that is theoretically based, which is different from the traditional empirically-based models. The coefficients in a theoretically-based model may be related to material properties, which facilitates the identification of better performing mixtures and the development of performance-based specifications for constituent materials.
Thus far, the research efforts in AMAG have produced a uniaxial continuum damage model. This model was developed by applying the elastic-viscoelastic correspondence principle to separate out the effect of viscoelasticity and work potential theory to account for damage evolution under loading and microdamage healing during rest periods. The resulting constitutive model can predict the hysteretic behavior of the material under both monotonic and cyclic loading to failure, varying loading rates, random rest durations, multiple stress/strain levels, and different modes of loading. Research has shown that this model is applicable to aged and modified asphalt mixtures as well as traditional mixtures.
The continuing research in AMAG includes the application of the current model to a number of mixtures to study the effects mixture properties such as gradation, asphalt and air void contents have on the model parameters. Current research also includes the development of a simplified fatigue model, a simple fatigue test method, and investigation of the effect of temperature. Research is also being performed to develop a multi-axial model that can describe both the fatigue and permanent deformation behavior of asphalt mixtures.
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