Rheological viscoplastic models of asphalt concrete and rate-dependent numerical implement

Based on the generalized plastic theory, a viscoplastic constitutive model is derived from Perzyna's theory of viscoplasticity and is used to model the ratcheting behavior exhibited by the mix. The evolution of the permanent strain with number of loading cycles is also captured. The loading surface is considered for the viscoplastic model of asphalt concrete (AC) according to Vermeer loading surface. A non-associate flow rule for the plasticity model as well as an evolution equation for hardening parameters is given. The viscoplastic component captures the rate-dependent behavior. The developed viscoplastic model takes into account the anisotropy in AC. Inherent anisotropy is introduced through the fabric tensor and considered by the preferred orientation of non-spherical particles. The developed damage model is incorporated in the viscoplastic model to capture the permanent deformation of AC. Numerical implementation and algorithm aspects of the multidimensional elastic-viscoplastic-damage model are presented. A robust integration algorithm for the nonlinear differential equations is carried out, which equations are solved by prediction-corrector method. Model results are compared to experimental observation. For the permanent deformation, results of the RSST-CH and Triaxial experimental are used to calibrate the model and test its prediction of different stress levels. RSST-CH is also modeled as a boundary value problem to assess the capability of the model to predict rutting in the pavement. (C) 2016 Elsevier Ltd. All rights reserved.