Research On Performances Of Modified Asphalt And Its Mixture For Venezuela Rock Asphalt(VRA)

Venezuela Rock Asphalt(VRA)is a kind of natural asphalt modifier with high content of asphalt,few impurities and abundant storage,which has broad application prospect,but there is a lack of systematic research on VRA at present.Therefore,the performances of VRA modified asphalt.and its mixture were studied through a large number of laboratory tests in this thesis,in order to provide basis for the promotion and application of VRA.1)The asphalt content of VRA is 96.93%determined by the combustiont method(538?)and solubility test.The content of asphaltene and colloid in VRA are higher by four-component test,which are 2.74 times of matrix asphalt.The results of X-ray diffraction test show that the main chemical components of mineral in VRA are CaSO4,CaS and SiO2,as well as a small amount of CaCO3.The results of infrared spectra analysis test prove that the process of modification of matrix asphalt by VRA is a physical mixing.Therefore,it can be stated that VRA is a kind of hard natural asphalt modifier.2)The preparation method of VRA modified asphalt was determined,and the internal mixing method was used to select five different kinds of VRA mixing amount(the mass ratio of VRA to VRA modified asphalt)from 0%to 20%at 5%interval,the conventional tests and SHRP tests of the performances of VRA modified asphalt were conducted respectively.The results show that with the increase of VRA mixing amount,the high temperature performance,temperature sensitivity and aging resistance of VRA modified asphalt can be improved significantly,but the low temperature performance is adversely affected.The results of correlation analysis show that the variation regularities of the performances of VRA modified asphalt evaluated by using the conventional test indexes and SHRP test indexes are consistent.3)According to the principle of equally replacing matrix asphalt and mineral powder with asphalt and mineral in VRA,the mixing amount calculation formulas of VRA modified asphalt mixture ratio design were obtained,and the "dry process" was determined more economical and practical after comparing different mixing processes.For this purpose,five different kinds of VRA mixing amount(the mass ratio of VRA to VRA modified asphalt mixture)were seleted from 0%to 1%at 0.25%interval,the Marshall tests and pavement performance tests of VRA modified AC-13C asphalt mixture were conducted respectively.The results show that VRA can significantly improve the high temperature stability,water stability and deformation resistance of asphalt mixture,but ruduce the low-temperature crack resistance,and has no obviously effect on impermeability and skid resistance at the same time.Analyzing comprehensively,the suitable mixing amount of VRA is recommended from 0.25%to 0.75%.Meanwhile,the results of economic analysis show that VRA modified asphalt mixture has a higher performance-price ratio than SBS modified mixture asphalt.In summary,the suitable mixing amount of VRA and the mix design method of its modified asphalt mixture proposed in the thesis can provide reference for its engineering applications.