Study On Influence Mechanism Of Mechanical And Drainage Properties Of Large Voids Asphalt Mixture

Functional asphalt pavement is the most representative road traffic facility of contemporary and future asphalt pavement in the world,and the large void asphalt mixture(OGFC)is one of the main materials that make up functional asphalt pavement,where the drainage performance is the main functional index of large void asphalt mixture.However,the mechanical properties of large void asphalt mixtures are not as good as those of dense or intermittent asphalt mixtures,and their strength indicators and stability are difficult to meet the requirements of the long-term road performance of road surfaces.Therefore,it is of great theoretical and practical value to study the meso structural characteristics of mechanical and drainage properties of different void asphalt mixture and their mutual influence mechanism.The meso structural characteristics and drainage performance of different void asphalt mixtures(especially large void asphalt mixtures)are related each other,in order to study the influence mechanism of their meso structural parameters on the drainage performance,in this research,the micro and meso structural characteristics and mechanical properties of different void asphalt mixtures are simulated first by using molecular dynamics(Molecular Dynamics,referred to as MD)and discrete element method(Discrete Element Method,referred to as DEM),and the relationship between the mechanical and drainage properties of different void asphalt mixture under the micro and meso structure are compared and analyzed.On this basis,through digital image processing technology and void characteristic parameter statistics software,the section image of the asphalt mixture specimens with different voids is processed,the meso structural characteristics of the asphalt mixtures with different gradations are discussed,and the influence of the meso structure on the mechanical and drainage properties of the large void asphalt mixture is analyzed,and then the influence factors of mechanical and drainage properties of the large void asphalt mixture are analyzed further.At the same time,based on the results of drainage performance test and the obtained meso structure parameters,the influence of various meso structure parameters(average void number of sections,total void area,void number above area of 10mm~2 or more,equivalent void diameter)on drainage performance is explored by using gray correlation theory,the influence mechanism of meso structure on the drainage performance of the large void asphalt mixture is further revealed.The results show that with the increase of void and the maximum particle size,the drainage performance of asphalt mixture is enhanced,and the increase of void and the maximum particle size can improve the drainage performance.The results of gray correlation analysis show that the equivalent void diameter is the main influence factor of the drainage performance of the road surface,the average number of void in the section is the least affected,and the drainage performance of the asphalt mixture depends on the number of effective voids.In order to further study the mechanical and drainage properties of the large void asphalt mixture,in this research,by using MATLAB image pre-processing and digital image processing techniques,the meso structural characteristics of the large void asphalt mixture are analyzed by extracting meso-images of the specimen cross-section.The research includes:the experiment of the mechanical performance of the large void asphalt mixture(rutting test,bending test,freeze-thaw split test and immersion Marshall test)and drainage characteristic test,the meso structure analysis of the large void asphalt mixture,and the influence of meso structural characteristics on the mechanical and drainage performance of the large void asphalt mixture.The results show that with the increase of the maximum particle size,the total number of void in the large void asphalt mixture and the number of void in the void area above 10mm~2are reduced,while the number of connected voids is increased,so the drainage performance of the asphalt mixture with the largest particle size is good,but it is susceptible to water damage,and the increase of the largest particle size of the asphalt mixture can increase the mechanical performance.The mechanical performance of the large void asphalt mixture is the prerequisite for studying its functional index,and the balance relationship between the two determines the application of the functional asphalt pavement.This study is not to solve the problem of insufficient mechanical characteristics of the large void asphalt mixture,but to study the mutual influence mechanism between the mechanical characteristics and drainage characteristics of the large void asphalt mixture,that is,the structural stability is good→the large void is guaranteed→the drainage characteristics are guaranteed.Therefore,in this study,by combining the mechanical and drainage characteristics of the large void asphalt mixture together,the meso structural characteristics and the mutual influence mechanism of the two are researched,it can provide some technical reference for the study of the functional indexes of the large void asphalt mixture(drainage asphalt pavement).The results of the study have some theoretical and practical value to the technical system of the large void asphalt mixture(drainage asphalt pavement).