An Improved Multistage Creep Recovery Test Procedure for Viscoelastic-Plastic Damage Model Calibration

The viscoelastic-plastic damage model has been widely used to predict the long-term performance of asphalt mixtures. However, it is challenging for obtaining model parameters to separate the total strain and determine the yield function. This study proposed an improved multistage creep-recovery test to simplify the acquisition of constitutive model parameters. The method was designed to identify the viscoplastic parameters by the equilibrium condition when the specimen was fully hardened and calibrate the damage parameters through the changes of modulus in the process of plastic development. The results indicated the proposed test is an effective method to calibrate the parameters of the viscoplastic damage model, as well as the nonlinearity between the stiffness and strength. In addition, it was found that the sigmoid function may be the more satisfactory choice to fit the cohesion excluding the damage compared with the negative exponential function.