Characterization of permanent deformation of an asphalt mixture using a mechanistic approach

Abstract

Viscoplastic constitutive equations offer improved prediction of the accumulated permanent deformation in comparison with linear elastic or viscoelastic models. An elastic-viscoplastic continuum model is proposed to simulate the permanent deformation of an asphalt mixture at WesTrack. After analysis of vertical compressive stress under the same loading condition and layer thickness at a WesTrack replacement section, strain rates were determined to characterize asphalt mixtures subjected to loading at a represent ative vehicle speed. Uniaxial compressive strength tests were conducted at seven different strain rates to obtain the material parameters of elastic-viscoplastic constitutive model. In addition, triaxial compressive strength tests were performed at a low strain rate and four different confinement pressures to obtain material parameters for the Drucker-Prager yield function. The test temperature was 60°C based on the critical temperature for permanent deformation at the field section. The developed model and its calculated parameters were used in finite element simulation of the Simple Shear Tests at Constant Height (SST-CH) and results were compared to experimental measurements at 60°C. Reasonable agreement was found between predicted results and the experimental SST-CH measurements indicating the validity of the model and its parameters.