Study On Preparation And Performance Evaluation Of SBS/SBR Composite Modified Asphalt For Extremely Cold And High Altitude Area

As a cementing material,asphalt has its unique performance,which largely produces an effect on the performance of asphalt mixture.Adding modifier in the asphalt can improve both its tolerance of high and low temperatures and anti-aging performance.Due to the lower temperature and the stronger ultraviolet radiation in the cold and high altitude areas,asphalt and asphalt mixture are prone to aging and casuing harmful effects such as pavement cracking.Special climate environment makes higher requirements on asphalt and asphalt mixture.Therefore,a type of composite modified asphalt are prepared which be suitable for the cold and high altitude areas in this paper,it can prolong the life of asphalt pavement.Based on compatibility principle of the modifying asphalt,this paper studied the effects of raw material type,modifier adding order and dosage on the performance of asphalt by tests of three major indicators,viscosity,segregation.The optimum modification process was determined by orthogonal test,and a kind of SBS/SBR composite modified asphalt was prepared.Matrix asphalt,SBS modified asphalt,SBR modified asphalt and composite modified asphalt were chosed for tests of TFOT,PAV,UV aging,it was studied that the effects of aging on the properties of modified asphalts at high and low temperatures by taking softening point difference and 5 degrees ductility retention rate as evaluate indicators.Rheological properties of modified asphalt were studied by the tests of DSR and BBR.The indexes include rutting resistance factorG*/sinδ,flexural stiffness modulus S and creep deformation rate M.The bonding ability and fracture resistance of modified asphalt were studied by the test of viscosity and toughness,the indexes include tensile compliance F,toughness,toughness,toughness ratio R.These four types of asphalt mixtures were used to prepare asphalt mixture for long-term heat aging ultraviolet aging tests,it was studied that the variation of high temperature,low temperature and water stability properties of modified asphalt mixture before and after aging by rutting test,marshall stability test,freeze-thaw splitting test and bending test.The indexes include dynamic stability,residual stability,freeze-thaw splitting strength ratio,flexural tensile strength,ultimate flexural strain and fatigue factor.Finally,by investigating the climate characteristics of Qinghai Province,the climatic zoning of asphalt pavement and the adaptability of asphalt in each climatic zone were analyzed,the suitable kings of asphalt for different areas were recommended.The results showed that the SBS/SBR composite modified asphalt has superior performance which prepared by the optimum preparation process and the optimum dosage of modifier and additive,its softening point can reach at 74℃,and the 5℃ductility can reach at 55 cm.Compared with SBS modified asphalt and SBR modified asphalt,the composite modified asphalt has the lowest modulus at low temperature,the maximum creep deformation rate and the minimum loss of toughness,and the best low-temperature performance after aging.SBS modified asphalt mixture and composite modified asphalt mixture both have good high-temperature rutting resistance,water stability and fatigue performance after aging,the latter has the best low temperature crack resistance after aging.Solar radiation should be taken into account in the climatic division of asphalt pavement in Qinghai province.On the basis of partitioning,suitable asphalt types for different partitions are recommended.