Energy-Based Kinetics Approach for Coupled Viscoplasticity and Viscofracture of Asphalt Mixtures

Permanent deformation and cracking of asphalt mixtures are common distresses of pavement structures. These two damage processes are usually coupled and occur simultaneously. The evolution speed of each process across the temperature spectrum determines which one is more obvious. To more realistically represent this phenomenon, a new approach that combines the energy-based mechanics and kinetics is proposed to separate and model viscoplastic deformation and cracking of asphalt mixtures in this study. First, based on the energy-based mechanistic (EBM) approach, the criterion for crack initiation of asphalt mixtures is formulated, and the dissipated pseudostrain energy for viscoplastic deformation and that for cracking (DPSEp and DPSEc) are separated at different temperatures. Then, an energy-based kinetics (EBK) approach is proposed with a dimensionless logarithmic rate for an energy changing process and the Arrhenius equation. The kinetic parameters include the activation energies and preexponential factors, which are determined from creep tests for different types of asphalt mixtures under different loading modes and aging conditions. Besides, the viscoelastic–viscoplastic–viscofracture model containing the kinetic models and parameters is established and the weak-form partial differential equations (PDEs) are implemented into a finite element program, COMSOL Multiphysics. The accuracy of the model is verified by the experiment results of asphalt mixtures. In addition, the numerical simulation using the models and parameters from the EBK approach is performed for a typical pavement structure. It successfully evaluates the distributions of viscoplastic strains in the surface layer.