Characterization of the nonlinear viscoelastic constitutive model of asphalt mixture

Asphalt mixtures are generally considered viscoelastic materials that exhibit time and frequency dependency and have been the subject of numerous studies. However, some studies have shown that the performance of asphalt mixtures changes with the magnitude of stress/strain, which is considered nonlinear viscoelasticity. Concurrently, the accurate establishment of an asphalt mixture constitutive model is the basis of the accurate prediction of the asphalt pavement me-chanical response. Hence, the nonlinear viscoelastic constitutive in asphalt mixtures is analyzed and established. First, the uniaxial compressive creep experiment was conducted for three types of asphalt mixtures subjected to 0.1-1.1 MPa. The Schapery, Findley and multiple creep integral models were adopted to characterize the nonlinear viscoelastic performance of asphalt mixtures. The results showed that it was difficult to establish the multiple creep integral model due to its complex kernel function. The processes of establishing the Schapery and Findley models were similar, and the fitting degree of the Schapery model was superior to that of the Findley model. Finally, a Schapery nonlinear viscoelastic model of asphalt mixtures was proposed at 20 and 35 celcius.