Microstructural viscoplastic continuum model for permanent deformation in asphalt pavements

Permanent deformation is one of the major distresses in asphalt pavements. It is caused mainly by high traffic loads associated with high field temperatures. An anisotropic viscoplastic continuum damage model is developed in this study to describe permanent deformation of asphalt pavements. The model is based on Perzyna's formulation with Drucker-Prager yield function modified to account for material anisotropy and microstructure damage. The material anisotropy is captured through microstructural analysis of aggregate distribution on two-dimensional sections of hot mix asphalt. A damage parameter is included in the model to quantify the nucleation of cracks and growth of air voids and cracks. A parametric study was conducted to demonstrate the sensitivity of the model to strain rate, aggregate distribution, and microstructure damage. Triaxial strength and static creep measurements obtained from the Federal Highway Administration Accelerated Loading Facility were used to determine the model parameters.