Application of Mixture Theory in the Evaluation of Mechanical Properties of Asphalt Concrete

Abstract

Asphalt concrete is a heterogeneous mixture of three constituents of asphalt binder, aggregate, and air void. The local volume fractions of these constituents vary spatially and therefore result in the spatial gradients of the local volume fractions. The local volume fractions and their spatial gradients are important field variables in mixture theory that predicts the mixture behavior out of the structure of the mixture and the properties of the constituents. In this paper, the fundamentals of mixture theory and a general method for solving boundary value problems using mixture theories were presented. A simplified mixture theory for two-constituent mixtures of solids and air voids was proposed to model the initial stress distribution of asphalt concrete under static loading. The analytical solutions of simple two-dimensional (2D) and one-dimensional (1D) cases using the simplified theory were obtained to illustrate how this theory predicts the effective stress distribution of a heterogeneous mixture. Methods to quantify the two field variables of the mixture theory, namely the local void volume fraction and its gradient, are developed using x-ray tomography imaging. The quantified void local volume fraction and its gradient for the specimens of mixes with known performance indicated a promising perspective for using mixture theory to evaluate the mechanical properties of asphalt concrete.