A Triaxial Viscoplastic Model with Temperature Dependence for Asphalt Concrete Permanent Deformation

Abstract

Asphalt concrete is a composite material comprised of aggregate skeleton and asphalt cement. Its permanent or viscoplastic (VP) deformation is characterized by time and temperature dependence, memory effect, and pressure sensitivity. To the best knowledge of the authors, there have been no VP models explicitly considering the nonlinear temperature effects in permanent deformation of asphalt concrete. In previous work, the authors developed a triaxial VP model that featured a VP relaxation spectrum and a modulus parameter [Formula: see text],[Formula: see text]. The spectrum was postulated as a material function representing the time dependence and memory effect, while [Formula: see text],[Formula: see text] was only a function of the stress condition to capture the pressure dependence. The objective of this study was to incorporate temperature dependence into the model. It was achieved by introducing the concept of VP shift factor solely to translate the relaxation spectrum. This strategy was inspired by the time–temperature superposition principle in the viscoelastic (VE) theory. The shift factor was identified experimentally at three temperatures different from the model calibration temperature. The VP shift factor function was thus established, and comparison with its VE counterpart showed that the VP response exhibited greater temperature sensitivity. Numerical simulation was conducted at several temperatures to illustrate the nonlinear temperature effects on the VP deformation and relaxation of the internal stress that served as the hardening/softening variable.