Distribution of Strains Within Hot-Mix Asphalt Binders: Applying Imaging and Finite-Element Techniques

Abstract

Because of several orders of magnitude difference between the stiffness of aggregate and binder and the randomness of the binder domain boundaries, the induced deformation under loading can result in a wide distribution of stresses and strains within each of the components. It is expected that although aggregates undergo small strains, most of the strain will accumulate within the binder. Although studies have covered the micromechanics of hot-mix asphalt (HMA), information about the actual typical distribution of asphalt binder domains in HMA and the resulting distribution of stresses and strains is scarce. In this study, advances in imaging techniques are applied to understand the distribution of binder and air voids in selected HMAs. The objective is to determine the strain distribution within the binder using digitized images analyzed with finite-element procedures. This approach captures the image of the specimen cross section and converts the image into finite-element mesh after image processing. The images are converted to finite-element mesh and the finite-element program ABAQUS provides numerical solutions to relate bulk stresses or strains applied to the asphalt mixture to stresses and strains within the binder domains. The results are presented including a summary of the distribution of directional binder film thickness and maximum strains in the mastic domain. Also included is a discussion of the effect of air voids and mineral fillers.