Self-Consistent Micromechanics Models of an Asphalt Mixture

Abstract

An asphalt mixture is a composite material consisting of three components: asphalt binder, aggregate, and air. The mechanical properties of asphalt mixtures are mostly evaluated from empirical approaches that are usually limited to measurement conditions. This paper takes a mechanistic approach by using micromechanics theory for composite materials to develop self-consistent micromechanics models for an asphalt mixture. The mixture analysis method described in this paper is applied to measured properties of an asphalt concrete mixture that is commonly used in Texas. These models are programmed in MATLAB using the system identification method and are applied to the analysis of the frequency-dependent magnitudes of the viscoelastic properties of an asphalt mixture at different aging periods. The inverse micromechanics model takes as input the volumetric composition of the mixture and the measured frequency-dependent bulk and shear properties of the asphalt mixture and the binder and extracts from them the bulk and shear properties of the aggregate. The forward micromechanics model takes as input the frequency-dependent bulk and shear properties of the aggregate and binder and produces the frequency-dependent properties of the asphalt mixture. It has been demonstrated that the inverse and forward micromechanics models are in fact the inverse of each other and that the inferred aggregate properties are realistic. These models provide a technique to catalog the properties of aggregates and use them in a computerized determination of the combinations of binders, aggregates, and air to produce the desired properties of asphalt mixtures.