Investigation About Impacts Of Coarse Aggregate Gradation And Morphology On Asphalt Mixture Stucture And Performance

The structural framework and the strength formation mechanism of asphalt mixture are closely related, and the coarse aggregate is one of the elements of the structural framework of asphalt mixture, so the gradation composition is bound to influence the structure and properties of asphalt mixture. On the other hand, as a typical structure of coarse aggregate, the content of flat and elongated particles has an important influence on the performance of asphalt mixture. However, in the existing studies, the researchers focused on the comparative analysis of the macro-performance of asphalt mixture when studying the problem. It was rarely based on the influence of the composition of asphalt mixture on its macro properties.Therefore, this paper focuses on the effects of coarse aggregate gradation fluctuation and the content of flat and elongated particles on the composition and properties of asphalt mixture, the relationship between structure and macro properties of asphalt mixture was established. The main contents and achievements of this paper are summarized as follows:Firstly, two kinds of asphalt mixture with typical gradation are taken as the research object, and the global structure parameters of specimens are obtained based on CT scanning imaging technology. With the help of digital image analysis technology, systematic study was carried out on morphological characteristics,surface topography and spatial information of voids, by using mathematical statistics to analyze meso structure parameters, establishing evaluating indicators of meso structure of coarse aggregate.Secondly, in order to quantify the influence of coarse aggregate composition and the content of flat and elongated particles on the mechanical properties of the viscoelastic behavior of the asphalt mixture, taking coarse aggregate gradation and flakiness content as variables to obtain the dynamic response characteristics under different environmental conditions of temperature and loading frequency. In view of the improved CAM model, fitting the results of the above material to the model,taking the viscoelastic parameters——Ge?Gg*?fc?me??m?ft,etc.——to implement quantitative analysis including the influence of coarse aggregate gradation and the content of flat and elongated particles on mechanical and viscoelastic properties of asphalt mixture. The results show that the change of coarse aggregate gradation and the content of flat and elongated particles has significant influence on the complex modulus, phase angle and viscoelastic parameters of asphalt mixture. On this basis, the partial correlation analysis method was used to evaluate the structure and mechanical properties of asphalt mixture in correlation.Finally, the method of partial correlation analysis is used to analyze the relationship between the structure and rheological time combining the evaluation method of anti-permanent deformation ability of asphalt mixture, and the results show that coarse aggregate gradation and the content of flat and elongated particles have remarkable influence on the deformation resistance of asphalt mixture. Based on the Burgers creep model, the viscoelastic parameters are obtained by fitting the creep curves, and the composition mechanism of creep with the variables——coarse aggregate gradation and flat and elongated particles content——is clarified. On this basis, the correlation between the structure and viscoelastic parameters of asphalt mixture is analyzed.In this paper, a series of research work has been carried out on the structural composition, viscoelastic properties and deformation resistance of asphalt mixture to clarify the influence of coarse aggregate gradation and flat and elongated particles content on the structure and properties of asphalt mixture, and on this basis, the correlation analysis of the composition and macro properties of asphalt mixture was realized.