Search

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. [ABSTRACT FROM AUTHOR]

The mechanical behavior of many bound granular materials such as asphalt mixtures is anisotropic in nature. However, the majority of the current mechanical tests and analytical models for asphalt mixtures are based on the assumption of isotropic material properties. This study investigates the stiffness anisotropy of asphalt mixtures using micromechanics-based models. The models’ parameters are obtained by quantifying the internal structure anisotropy in terms of the preferred orientation of longest axes and contact normals of aggregates. Image analysis techniques are used to conduct the internal structure measurements. The orientations of the longest axes are found to be easier to measure, and better descriptors of anisotropy, than the contact normals. Finite-element analyses of the internal structure are also used to provide insight into the mixture stiffness anisotropy. The mixture properties are selected to represent a wide range of temperatures. The stiffness in the horizontal direction is shown to be as high as 30% more than the stiffness in the vertical direction. The stiffness anisotropy decreases with a decrease in the mixture temperature. The finite-element results are shown to have very good correlation with the results of the micromechanics model derived based on the orientation of the longest axes of aggregates. [ABSTRACT FROM AUTHOR]