Determination of Asphalt Binder VECD Parameters Using an Accelerated Testing Procedure

Fatigue characteristics of asphalt binder have an important role in asphalt mix resistance against cracking. Viscoelastic Continuum Damage (VECD) analysis of asphalt binders has been successfully used in highway research works in order to predict fatigue behavior of hot mix asphalt (HMA). In this method an intrinsic property of the material, called damage function is obtained which is independent of damage path. However, achieving damage function needs application of various loading paths and a trial and error procedure. In this study, a quick characterization procedure has been proposed to implement VECD analysis that results in fatigue prediction of HMA. The procedure is comprised of a testing setup, along with the analysis required to derive VECD parameters from experimental data. The test consists of a stepwise loading scheme including a few strain levels with relatively large increments in between. Subsequently, an optimization method has been introduced to be performed on the test results, to yield damage function, i.e. modulus as a state function of Internal State Variable (ISV). The analytical framework leading to the optimization problem, along with its solution methods are presented. Consequently, the fatigue life prediction model has been obtained, relating the change in shear modulus to loading conditions such as strain level and frequency. Eventually, the introduced characterization method was validated, comparing the results with those achieved in conventional procedure. The validation showed that the results of optimization and conventional methods agree, with an acceptable precision.