Study On Low Temperature Properties Of Calcium Sulfate Whiskers And Polyester Fiber Composite Modified High Modulus Asphalt

Asphalt roads are widely used in highways of all grades due to their advantages such as driving comfortable type,low noise,and short construction time.During the use of asphalt roads,there will be many diseases:rutting,low-temperature cracking,crowding,pits,tumbling,etc.Among them,low-temperature cracking is one of the important issues affecting the service life and performance of asphalt roads.The low temperature performance of the asphalt mixture is affected by many factors,such as the temperature sensitivity of the asphalt,the oil-stone ratio and the composition of the mixture.In this paper,calcium sulfate whiskers and polyester fibers are used to modify the asphalt mixture.Calcium sulfate whiskers are blended by a "wet" process,calcium sulfate whiskers(CSW)are added to the asphalt,and calcium sulfate whisker modified asphalt is prepared by mechanical stirring.The polyester fiber is mixed into the mixture through a "dry"process,and the polyester fiber and the aggregate are mixed and mixed dry.In this paper,by testing the performance of CSW modified asphalt and the low temperature performance of composite modified asphalt mixture,the following conclusions are reached:(1)Test penetration degree,penetration index(PI),equivalent brittleness point(T1.2),equivalent softening point(T800),softening point and ductility of CSW modified asphalt through penetration test,softening point test and ductility test Point and ductility index.The test results show that when the amount of CSW in asphalt ranges from 0 to 10 percent,and the penetration index of asphalt is reduced from-1.3457 to-0.9173.The lower the penetration index,the lower the temperature sensitivity and the lower the temperature.T1.2 reflects the low temperature crack resistance,and with the increase of CSW,T1.2 reduces from-7.6? to-10.2?,which comes to a confluence that low temperature performance of asphalt increases with the increase of CSW.When CSW is added to asphalt,the consistency of the asphalt becomes larger,the fluidity decreases,and the viscosity increases.The softening point and equivalent softening point of the asphalt are increased,indicating that CSW can improve the high temperature performance of asphalt.(2)Analyze the applicable conditions of different gradations,and select gradation AC-13 that is most suitable for the study of this paper.Through aggregate tests,the gradation of the minerals was determined based on the Fuller gradation theory.The optimum oil-stone ratio of the composite modified asphalt mixture was determined through the Marshall test.The results show that CSW and polyester fibers will increase the amount of asphalt in the mixture.This is because the fibers are oil-absorbing,and CSW also consumes more asphalt by reducing the fluidity of the asphalt and increasing the consistency of the asphalt.The increase in the amount of asphalt increases the thickness of the asphalt film in the mixture.The increase in the thickness of the asphalt film also helps to improve the low temperature performance of the asphalt mixture.(3)The low-temperature performance of the asphalt mixture is tested through a low-temperature bending test.In this paper,the energy index-the critical value of the bending strain energy density is used to evaluate the low-temperature performance of the asphalt mixture.The strength and deformation ability of the asphalt mixture at low temperature are considered comprehensively.The results show that when the content of CSW in the asphalt is 4%and the content of polyester fibers in the aggregate is 6 ‰,the low temperature performance of the composite modified asphalt mixture is the best.(4)The gray correlation analysis method was introduced to analyze the bitumen-aggregate,the bending tensile strength of the mixture,the bending tensile strain,the penetration index of the asphalt,and the correlation between the equivalent brittle point and the low temperature performance of the asphalt mixture.The correlations of the critical values of the energy density are arranged in descending order:flexural tensile strain>flexural tensile strength>T1.2>bitumen-aggregate>PI.