Study On Performance And Mechanism Of SMA-13 Asphalt Mixture Reinforced By Flocculent Basalt Fiber Modified By Silane Coupling Agent

With the rapid development of economy,the problems of large-scale and heavy load vehicles brought by the prosperity and development of China’s logistics and transportation industry have caused irreversible diseases such as rutting,crack,water damage and so on.In recent years,the modification of asphalt pavement by adding fiber to improve its road performance has attracted the attention of more and more industry scholars.Although wood fiber has been widely used in SMA-13 asphalt mixture system because of its excellent oil absorption,more studies have found that wood fiber in asphalt pavement has disadvantages such as easy degradation,poor high-temperature stability and easy water absorption,which affect the performance of asphalt mixture.Basalt fiber has good mechanical properties and high temperature stability,and can be recycled,which makes it widely used in asphalt mixture.The basalt fiber selected in this paper is a functional high-performance flocculent basalt fiber made of molten mineral aggregate by centrifugal method.Based on the comparative study of the three index properties of different flocculent basalt fiber and wood fiber reinforced asphalt,in order to further improve the interfacial adhesion between flocculent basalt fiber and asphalt and improve the adsorption performance of fiber to asphalt,The flocculent basalt fiber was modified with silane coupling agent,and the road performance of SMA-13 asphalt mixture was tested.The main research work and conclusions are as follows:Firstly,the surface coupling agent modification of flocculent basalt fiber is studied in this paper.Seven kinds of silane coupling agents containing different characteristic functional groups were selected to compare and study the hydrolysis methods of different coupling agents.It was concluded that the best hydrolysis conditions of silane coupling agents were water:absolute ethanol = 3:7.For other types of silane coupling agents except those containing amino characteristic functional groups,glacial acetic acid was added to adjust the p H value to 3-5,and the hydrolysis time was 1H,followed by surface free energy(SE),asphalt holdup FTIR and SEM were used to characterize the changes of surface morphology,basic properties and functional groups of flocculent basalt fiber modified by silane coupling agent.The results showed that there were attachments on the surface of flocculent basalt fiber after modification,the roughness increased,the asphalt holdup and surface oil content increased,and different characteristic functional groups could be detected by infrared absorption spectrum with different types of modifier.Then,the properties of flocculent basalt fiber reinforced asphalt before and after surface modification are compared.The influence law and mechanism of various factors on the three indexes of SBS modified 70# asphalt(softening point,cone penetration and force ductility)are studied from the perspective of fiber type,content and coupling agent type.The research results show that in the range of 0-6% mass ratio,the performance of asphalt first increases and then decreases with the content of fiber,and reaches the peak at 4%.The flocculent basalt fiber modified by KH550,UP602 and UP312 coupling agent can improve the performance of three indexes of asphalt.After modified by KH560,KH580 and A151,the performance of fiber mixed into asphalt decreases.KH570 modified fiber has no obvious effect on the performance of asphalt.Through mechanical analysis,it is concluded that the reason is that the surface roughness of flocculent basalt fiber increases after modification and organic modifier is attached,At the same time,due to the existence of characteristic functional groups of modifier,the interfacial adhesion between fiber and asphalt can be improved;In addition,the calculation results of adhesion work show that the flocculent basalt fibers modified by different silane coupling agents have different effects on the adhesion work between fiber and asphalt,resulting in the difference of asphalt properties.Finally,the influence of modified flocculent basalt fiber on the pavement performance of asphalt mixture is studied.Through the mix proportion design,the optimal mix proportion and asphalt aggregate ratio of modified flocculent basalt fiber and wood fiber reinforced SMA-13 asphalt mixture are obtained.The high-temperature rutting,low-temperature crack resistance and water stability of the two kinds of fiber mixtures are compared and studied.Through the research on the road performance of flocculent BF asphalt mixture modified by four coupling agents,the influence of the characteristic functional groups of each coupling agent on the road performance of asphalt mixture is verified again.The results show that the road performance of surface modified flocculent basalt fiber mixture is better than that of wood fiber mixture.KH550 modified,UP602 modified and UP312 modified flocculent BF all improve the road performance of asphalt mixture to varying degrees,while KH570 modified flocculent BF has little effect on the road performance of asphalt mixture.