Research On The Graded Segregation Characteristics Of HMA

Large engineering practices have proved that the gradation segregation of HMA is an important reason to cause early damage to asphalt pavement.The issue of HMA segregation has posed heated researches at home and abroad in recent years,however,most researches concentrate on construction technology,or countermeasures against equipment and management prevention and control,but fail to solve problems from the perspective of material designing,lacking effective testing methods and appraisal indexes on the segregation property of aggregate and HMA.Without organic integration between the application performance and technology property of HMA.Aiming at these problems,this paper employs the sliding-plate method and material-pile method to perform test researches on the segregation property of aggregate and HMA,from the starting point of segregation property of HMA which is a kind of granular mixture with certain viscous.Through appraisal on the gradation of typical HMA,the paper preliminarily proposes the segregation appraisal system focusing on heaping method,including 3 levels of aggregates,HMA and field,which have provided a necessary basis for the integration between application performance and technology property from the designing perspective.The laws of size fraction mutual interference are discovered in the paper through multiple size fraction interference and gradation mutual interference tests by employing the sliding plate method in the research on the interference property of aggregate,starting from the single size fraction test.The tests indicate that a size fraction distribution with a good overall effect is existed,because of the dual natures of interference.Based on the above-mentioned mechanism research,the paper proposes the basic principle of "concentrating on medium size fraction,controlling the coarse fraction and fine one" for the designing of segregation -resistant HMA. The material-pile method is employed in the paper to perform research on the segregation property of HMA,and the function of viscosity is elucidated.Not only the segregation of HMA is lighter than the one of the aggregate,but also the overall segregation laws are consistent.The segregation appraisal system established by the paper is employed to perform the application performance test of Marshall Index on the common gradation types. The test research and field verification indicate that it is operable to adjust the size fraction distribution to integrate the application performance and segregation property.In order to verify the test results,the paper uses the application experiences of Shanghai-Nanjing Expressway,Shenyang-Shanhaiguan Expressway,etc as basis,besides in combination with the field monitoring on overhaul projects of Tie-Si Expressway and Shenyang-Shanhaiguan Expressway.The paper also analyzes the NAPA and proposes the limitations existed in the gradation designing principle related to segregation-resistance,and proposes the basic principle in segregation-resistant HMA designing.It furthers the research on the integration between the application performance and technology performance from the designing perspective.The discrete element method is employed in the paper to perform exploratory research of granular segregation simulation on the graded mixture,the simulation result is generally consistent with the test results of sliding-plate method and material-pile method,and the question of granular segregation is further discussed from the perspective of digital simulation.