A theoretical and numerical study of the micromechanical behavior of asphalt concrete was undertaken. Asphalt is a heterogeneous material composed of aggregates, binder cement, and air voids. The load-carrying behavior of such a material is strongly related to the local load transfer between aggregate particles, and this is taken as the microstructural response. Numerical simulation of this material behavior was accomplished by developing a special finite element model that incorporated the mechanical load-carrying response between the aggregates. The finite element scheme incorporated a network of special frame elements, each with a stiffness matrix developed from an approximate elasticity solution of the stress and displacement field in a cementation layer between particle pairs. A damage mechanics approach was then incorporated within this solution, and this approach led to the construction of a softening model capable of predicting typical global inelastic behavior found in asphalt materials. This theory was then implemented within the ABAQUS finite element code to conduct simulations of particular laboratory specimens. A series of model simulations of indirect tension (IDT) tests were conducted to investigate the effect of variation of specimen microstructure on the sample response. Simulation results of the overall sample behavior compared favorably with experimental results. Additional comparisons were made of the evolving damage behavior within the IDT test samples, and numerical results gave reasonable predictions.
Abstract