Research On Characterization Of Meso-Structure In Asphalt Mixture Based On Topology Optimization

For aggregates and air voids as meso-structures, their physical properties,geometric shape and the interaction between them have a great influence on the mechanical properties of asphalt mixture. Traditional design method for asphalt pavement phenomenologieally focuses on the mechanical properties of asphalt concrete materials from a macro perspective, with an assumption that the material is isotropic and homogeneous, which is difficult to reveal the physical mechanism of materiai deformation and distress. The asphalt mixture is much more complicated. In this dissertation, asphalt mixture is regarded as a multi-phase composite material system, and its meso-structure is preliminarily simulated and optimized.Based on the Monte Carlo method, two-dimensional finite elment model is established for the meso-structure of asphalt mixture in the cases of both aggregates and air voids, the effects of aggregates or air voids with different sizes, shapes, and locations subjected to the same loading conditions are studied in asphalt mixture in this dissertation. The specific results obtained in this dissertation are as follows:(1)By changing the aggregates size, air voids and their arrangement in the models, the correlation between stress-strain properties and the micro-structures including air voids, aggregates shape as well as their distribution characteristics. Moreover, the mechanical characteristics of aggregates and the damage trend of within micro in structure asphalt mixture of the trend is summarized.(2)Through simulation of the models with different air void contents, topology optimization is carried on and the relationship between strength of asphalt mixtures and the air void content is verified.(3)According to the characteristics of different gradations, three representative asphalt mixture models with different gradations are established to discuss the mechanical characteristics of aggregates in vertical and horizontal direction within the three structures. In addition, the load capacity of these asphalt mixtures with different gradations are compared. All of these will provide a basis for asphalt mixture design.(4)Asphalt mixtures of different gradations are simulated and their mechanical properties are compared. Then the optimal mineral aggregate gradation is obtained by selecting the gradations with good properties, furthermore, comparing with the design specifications.