Simulation Of Influence Of Aggregate Homogeneity On Mechanical Properties In Asphalt Mixture Based On Discrete Element Method

The homogeneity of asphalt mixtures is the overriding factor leading to premature damages on asphalt pavements, and it also dominates the mechanical properties and service life of bituminous pavements. Asphalt mixtures are the composite granular materials composed of aggregates, asphalt mastics and air voids, with complex physical and mechanical responses. The general laboratory tests and finite element methods based on the continuum mechanics cannot reveal the complicated mechanism essentially. Therefore, based on the digital image processing (DIP), the influence of the homogeneity of asphalt mixtures on the various mechanical performances is investigated using Discrete Element Method (DEM).Firstly, the interface programs with aggregates of real boundaries, polygons and ellipses are written into particle flow code (PFC) based on DIP, and the two-dimensional discrete element models of horizontal and vertical cross sections in asphalt mixtures are established. Secondly, the indirect tensile tests of asphalt mixtures in low temperatures are simulated numerically, and the influence of the crushing of aggregates, air voids and geometry of aggregates is studied; based on time-temperature superposition, the uniaxial compression tests, and uniaxial penetration tests are simulated with the Burgers model, and the different loading rates, micro parameters in Burgers model are analyzed; and then the effects of the aggregate distribution in different asphalt mixtures on the various mechanical properties are studied. The laboratory tests above mentioned are carried out to verify the influence of homogeneity in asphalt mixtures on the mechanical properties of the DEM. Thirdly, the uniaxial static creep tests as one of pavement performances are simulated based on the servo-mechanism in PFC, and the influnce of aggregate homogeneity on the creep performance is investigatied.The research results indicate that the geometry of aggregates, air voids, micro parameters and loading rates have great influence on the various mechanical properties of asphalt mixtures. Based on the aggregate distribution, the homogeneity of asphalt mixtures has a good correlation with the variations of mechanical properties, and the gradation and the normal maximum aggregate size have a significant effect on the homogeneity of asphalt mixtures.