Research On The Performance Of High-viscosity Modified Asphalt And And Its Mixture Mesoscopic Void Characteristics

With the promotion of “sponge cities” and “low-impact development” concepts,permeable pavement has become a hot spot in Chinese road construction.Permeable asphalt mixture has rich and complex voids structures,which make it have excellent permeability.At the same time,its internal structure is directly corroded by the environment,causing the asphalt and aggregate to be easily stripped.The adhesion and adhesion between the high-viscosity modified asphalt and the aggregate are very high,which can meet the durability of the permeable asphalt pavement and the strength during service.At the same time,most of the current research on the permeability of asphalt mixtures focuses on establishing the relationship between porosity and permeability coefficient.However,a large number of studies have shown that the permeability of asphalt mixtures is greatly affected by the characteristics of the microscopic void structure.Therefore,research on the performance of high-viscosity modified asphalt and its mixture mesoscopic void characteristics has important practical significance for the promotion and application of permeable asphalt pavement.In this dissertation,the basic properties,rheological properties,and aging properties of rotating film were studied in laboratory on high-viscosity SBS modified asphalt with HVA contents of 8%,10% and 12%.The results show that when the HVA contents is 12%,the performance of the modified asphalt is good.The microscopic morphology and chemical composition of high-viscosity modified asphalt were studied by optical microscope,Fourier infrared spectroscopy and thermogravimetric analysis.The results show that HVA helps the polymer phase to form a spatial network structure.The modification of SBS asphalt by HVA is to physically increase the viscosity without generating new functional groups.The gradations of PA-13 permeable asphalt mixture and their optimal asphalt dosage were determined through voids ratio verification test,the Cantabro test,and the Schellenberg binder drainage test,and their performance were studied.The results show that the void ratio of 3# gradation is about 21%,the optical asphalt dosage is 4.5%,and the performance meets the specification requirements.Since the connected voids of 3# gradation is lower than 1# gradation,its anti-clogging performance is slightly worse than 1# gradation.CT scanning technology and digital image processing technology are effective tools for studying the microscopic voids structure characteristics of asphalt mixtures.This dissertation used CT technology to obtain the internal structure image of the permeable asphalt mixture.Based on MATLAB,the characteristics of the voids structure of the two-dimensional cross-section of the permeable asphalt mixture were characterized;through the Python programming language,a connected voids recognition algorithm based on the color channel merging technology was proposed,and the three-dimensional volumetric microscopic voids structure characteristics were characterized.The results show that the characteristic parameters of the microscopic voids of the two-dimensional cross-section are distributed uniformly along the height of the specimen.The variation coefficient of the cross-sectional voids distribution fluctuates slightly along the height of the specimen,which means voids distribute uniformly along the height of the specimen.The calculated value of the connected voids ratio is close to the measured value in the experiment,which means the connected voids recognition algorithm based on the color channel merging technology is reliable.The cross-section connected porosity is uniformly distributed along the height direction of the specimen.The specific surface area increases with the increase of the connected porosity.Based on the constant head method,a device for measuring the permeability coefficient of permeable asphalt mixture was developed.The Kozeny-Carman equation was improved based on the test results of permeability coefficient and the microscopic characteristics of the connected voids,and a permeable asphalt mixture permeability model was proposed.