Micromechanical modeling approach to predict compressive dynamic moduli of asphalt mixtures using the distinct element method

A clustered distinct element method (DEM) approach is presented as a research tool for modeling asphalt concrete microstructure. The approach involves the processing of high-resolution optical images to create a synthetic, reconstructed mechanical model that appears to capture many important features of the complex morphology of asphalt concrete. Uniaxial compression tests in the laboratory were employed to measure the dynamic modulus of sand mastic (a very fine sand-asphalt mixture) and asphalt mixtures at three temperatures and four loading frequencies. For a coarse mixture considered in this study, it was found that a two-dimensional (2-D) clustered DEM provided good estimates of mixture dynamic modulus across a range of loading temperatures and frequencies without calibration. However, for a fine-grained mixture, the uncalibrated predictions of the 2-D model were found to reside near the lower theoretical bounds and well below experimentally determined moduli, most likely because of current limitations in scanning and modeling resolution and the nature of the 2-D microstructural description. Work is under way to extend the model to three dimensions and to consider linear viscoelastic behavior in the mastic. That notwithstanding, the current modeling approach was successfully implemented in recent follow-up studies to portray bulk material behavior hi conjunction with fracture models to study crack behavior hi hot-mix asphalt