Three-Dimensional Microstructural-Based Discrete Element Viscoelastic Modeling of Creep Compliance Tests for Asphalt Mixtures

Microstructural-based discrete element (DE) models have been used for a better understanding of asphalt pavement concrete since the late 1990s. Most current studies have been done with two-dimensional (2D) models. Moreover, elastic models are primarily employed for simulation of an asphalt matrix's time-dependent behaviors. A 2D model is too simple to capture the complex microstructure of asphalt concrete, and an elastic model is not sufficient for simulating an asphalt matrix's viscoelastic behaviors. Therefore, it is necessary to consider a three-dimensional (3D) viscoelastic model for microstructural-based DE simulation of asphalt mixture behaviors. Currently, it is easy to build such a 3D microstructural-based DE viscoelastic model using the existing techniques presented in the previous studies. A major challenge, however, is to reduce the computation time to run the 3D microstructural-based DE viscoelastic modeling process which is extremely time-consuming. The primary objective of this paper is to simulate and analyze creep responses of an asphalt mixture with a 3D microstructural-based DE viscoelastic model. A key task in this study is to develop an approach to reduce the computation time with the time-temperature superposition principle. Using this developed approach, creep compliance tests of an asphalt mixture under temperatures of 0, -10, and -20 degrees C, were simulated with a microstructural-based DE viscoelastic model. Additionally, a DE elastic model was also employed and compared with the viscoelastic model. It was observed that (1) the computation time was reduced to several hours from several decades and (2) the DE viscoelastic model, the DE elastic model, and the experimental measurements yielded similar results.