Influence Factors On Properties Of Drainage Asphalt Mixture

With high void and better surface slip friction, drainage asphalt pavement can rapidly expel waterlogging in the rain, reduce road splash, avoid hydroplaning,greatly improved traffic safety,and decrease noise in driving, thus improving driving environment. In order to further optimize overall performance of drainage asphalt mixture, it is important to research the key factors in affecting the property of asphalt mixture from test method and material composition in the dissertation.The dissertation focuses on the specimen molding methods, run-off testing methods and density testing methods. To analyze the change of volume parameters, the specimens were molded by Marshell method and SGC method, and it is found that the indicators are in agreement by two-sided Marshell compaction and SGC compaction in 50 times, showing that it can replace each other under these conditions. SGC can evaluate the drainage asphalt mixture properties and compaction characteristics by locking point, however, Marshell can not,.So SGC is priority under a permittable condition. The locking point of gneiss,basalt,diabase mixture is 64 times,65 times and 60 times respectively, which showed that three kinds of mixtures had reached a relatively stable state after 65 times. By comparing the three run-off methods of mesh basket method,beaker method,enamel plate method, the mesh basket test with test tempreture 185℃was choosen for drainage asphalt mixture as a standard test method for analysis of run-off tset, and ratio of run-off loss should be less than 0.8%. The effect of the calculation method, the vacuum method, solvent and the impregnation on the maximum theoretical relative density is comparied and analyzed And the measured results show that the maximum theoretical relative density using the vacuum method with vacuum time around 15min is reasonable when the mixture evenly dispersed. Using of Volume method and Corelok vacuum sealing method the compacted specimen bulk specific gravity is measured, and the results show vacuum sealing method has high precision with less influence of human disturbance, Therefore, the vacuum seal is recommended measuring the gross volume of the specimen relative density. In addition, it is suggested that the design porosity of the vacuum sealing method is 16% and connectivity porosity is more than 14.5%.For impact factor of raw materials, the dissertation focuses on the asphalt type,coarse aggregate type and flat and elongated particle content on drainage asphalt mixture performance. The results showed that the 60℃dynamic viscosity is the key factor of drainage asphalt mixture properties. So when meeting the regulatory requirements, it should be chosen that asphalt of higher value of 60℃dynamic viscosity. With the higher content of the flat and elongated particle in coarse aggregate, aggregate get broken to refine the gradation when molding the specimen by Marshell or SGC,.Under this circumstance, the connected porosity and drainage function decreased, So the dissertation proposed that the flat-elongated coarse aggregate content of drainage asphalt mixture should not exceed 12%.