Study On Mesostructure And Microstructure Of Vacuum Compaction Asphalt Mixture

Pavement performance is affected by asphalt mixtures and construction technology and other factors, the bad compaction quality in the construction process is one of the main causes of road short life, pavement compaction cost is only one small fraction of the total cost of the road construction. Therefore, that is the most economical way to improve compaction pavement quality. Gas closed in asphalt pavement forms gas spring to limit compaction equipments’ ability, there is also a room to improve compaction quality and efficiency. In order to improve the quality of compaction and reduce air void ratio, this paper proposes vacuum compaction technology, intending to solve the existing problems of compaction. In order to explore the vacuum compaction impacting on macroscopic properties of asphalt mixture, a cold mix asphalt for studying in this paper, analyzing vacuum compaction impacting on mesostructure and microstructure of asphalt concrete, based on digital image processing and asphalt concrete microstructure analysis methods.In this paper, using CT tomography to obtain cross-sectional images of asphalt mixture specimens under static compaction, static compaction+vacuum, vibration compaction, vibration compaction+vacuum, this four kinds of conditions, using MATLAB image processing tools to obtain void characteristics of specimens’ CT scanning images, combining with scanning electron microscopy(SEM) to analysis asphalt cement-aggregate adhesion properties. The results show: under each conditions, internal layer air void ratio distribution of the specimen exists unevenness, throughout the specimen height from bottom to top, air void ratios are bigger on the top and at the bottom, and smaller in the middle of the specimen, and the entire air void ratio has gradually decreasing tendency; air void ratio of asphalt mixture is different under different conditions, in the same experiment condition, air void ratio and void equivalent diameter of asphalt mixture are significantly reduced under vacuum situation, decrease respectively by more than 4.8% and 4.9%; Compared with not vacuum compaction, micro-cracks in asphalt mortar-aggregate interface of asphalt mixture under vacuum compaction are fewer, cracks’ width is narrower. asphalt splitting strength test shows, the better mesostructure and microstructure of asphalt mixture under vacuum compaction, the higher asphalt mixture splitting strength, which increases by more than 5.7%.The research results indicate that vacuum compaction can reduce air void ratio of asphalt mixture and air void size, decrease asphalt mixture micro-cracks, improve the performance of asphalt mixture.