Study On Segregation Of Pavement Materials Based On Granular Characteristics

Asphalt pavement is the main type pavement structure of China’s highway. Asphalt mixture segregation is one of the main reasons for early damage of asphalt pavement. There are many research for the asphalt mixture segregation have carried out at home and abroad, which mainly concentrated in evaluation criteria for segregation, the effects of segregation on other pavement performance. All of these belong to analysis after the fall of segregation; it is difficult to resolve from the source of asphalt mixture segregation problem. For more effective control of segregation, the main purpose of this paper is to study the mechanism of segregation, the impact of material properties on segregation of asphalt mixture from the motion characteristics of particles based on granular material characteristics.Combined with the production process of asphalt mixture, three test methods to the processes:material piles forming, discharge from silo and undergoing vibration were put forward, which would be used to observe the motion characteristics of material during the three processes and analyze material segregation. Based on a great deal tests, deeply understand the particles’motion characteristics of the various stages, and then analyzes asphalt mixture segregation pathogenesis at various stages of the production. Permeation of fine aggregate in material piles, the motion distance difference of particle with different size on rough slope, and particle convective motion produced by the exciting force are the reasons of asphalt mixture segregation at different stages.Based on the test for the process of discharge from silo, the effects of material properties for segregation are analyzed. the uniformity of aggregate angularity, gradation differences, and bonding effect of asphalt all effect the segregation of the asphalt mixture, but the impact of each factor are different. On the whole, the difference of spatial structure is the most fundamental reason for segregation in asphalt mixture. Reasonable grading design can effectively reduce segregation in asphalt mixture from source. From the point of segregation and road performance, the recommended gradation is the one with skeleton-dense structure. Grey Correlation Analysis of segregation and aggregate size interval indicates that the key size interval for asphalt mixture segregation is4.75mm-9.5mm.Based on the understanding of the segregation mechanism, technical measures to decrease the asphalt mixture segregation are also proposed.