Microstructure-Based Visco-Elastoplastic Continuum Model of Asphalt Concrete

Asphalt concrete is a heterogeneous and multi-phase material that consists of aggregates, asphalt binder, and pores. These components create a complex microstructure. There is no consensus on how to quantify the microstructure and the required parameters from two-dimensional images. The load transfer can be managed by aggregate-aggregate or aggregate-mastic interactions that depend on the gradation, aggregate internal structure, and asphalt binder viscoelastic properties. The most important internal structure indices affecting the behavior of HMA are aggregate orientation, contact orientation, contact length, and number of contact points. In this paper, the influence of aggregate structure and binder viscoelastic properties on viscoelastic and visco-elastoplastic response of asphalt concrete is investigated for mixtures with different aggregate gradations and types of asphalt binders. Two factors were defined that describe the mechanical properties of the mixture to its microstructure; aggregate structure factor (ASF) and binder irrecoverable strain factor (ISF). ASF as a function of the aggregate internal structure relates the aggregate geometry and stresses to the stiffness of the asphalt mixture. Binder ISF describes the role of the aggregate structure in the accumulation of permanent strain in asphalt mixtures.