Research on Asphalt Mixture Bending Test and Micromechanical Evolution Based on 2D Discrete-Element Method

Abstract

The damage of asphalt mixture is closely related to its internal material heterogeneity and discontinuity. The mechanical evolution of asphalt mixture is analyzed by meso-mechanics theory, which is very important for revealing the failure mechanism of asphalt pavement. In this paper, the two-dimensional (2D) bending discrete-element model of asphalt mixture was established based on the meso parameters and pictures of the model determined by practical experiments. The process of meso-crack formation and propagation between particles of asphalt mixture under a certain load rate was analyzed. The distribution and transmission of stress and the evolution of the displacement field were also analyzed. The results show that the error between the model bending test and the actual standard test is within 10% (maximum bending strength and maximum bending strain). The model test results show that the discrete-element method can simulate discontinuous and heterogeneous materials well. Under the action of external load, the vertical displacement of coarse aggregate particles is much larger than the horizontal displacement. The displacement of asphalt cement granules is slightly larger than that of coarse aggregate granules. The number of microcracks in the model increases slowly in the early stage and quickly in the later stage. Finally, macroscopic cracks are generated. These macroscopic cracks generally extend along the edges of coarse aggregate particles and where the adhesion of asphalt mortar particles is weak. The force chain diagram between particles in the discrete-element model had both regularity and great discreteness. The results showed that the discrete-element method could not only obtain the internal stress and displacement of the asphalt mixture, but also reveal the mechanical evolution behavior between the particle flows of the asphalt mixture.