Multi-factor Coupling Damage Characteristics Of Asphalt Binder Under Salt Erosion Condition

The durability of asphalt mixture has always been one of the important issues of concern to the road engineering community at home and abroad.Whether it is frequent sea fog,coastal areas with salt and high humidity,or salt lakes and saline soils inland,the corrosive media such as chloride and sulfate enriched in the natural environment often make the performance of road engineering materials.The deterioration is serious,resulting in a shortened service life of the road.In addition,in order to ensure smooth road traffic and safe driving in ice and snow weather,the cheap and cheap method of salt spreading is common;or another way to solve this problem by using salt-containing snow melting and anti-icing materials.In either case,the salt has a continuing negative effect on the asphalt pavement material in the form of a solution or crystal.According to the "internal etch" condition of salt,the basic properties of salt-mixed asphalt cement were evaluated by softening point,penetration,penetration,ductility and Brookfield viscosity during the test period;direct tensile test and bending were adopted.Beam rheological test(BBR)is used to study the low temperature rheology of salt-filled asphalt cement under different age conditions.Based on surface wetting theory,surface free energy,polar component and non-polar component are used to characterize asphalt.The cohesiveness of the binder;the microscopic mechanism of the salt-incorporated asphalt cement was investigated by means of scanning electron microscopy(SEM)and infrared spectroscopy(FTIR).According to the "outer eclipse" condition of salt,the freeze-thaw cycle test of matrix asphalt and rubber powder modified asphalt under salt solution immersion conditions,the tensile peak and pull of the force measurement test were used.Extensibility index analysis of asphalt tensile properties under salt-freezing cycle;characterized bydissipative energy ratio Wd(t)/Ws and creep compliance derivative J’(t)Viscoelastic properties of asphalt;tensile strength of the asphalt-aggregate system was evaluated by tensile strength of the pull test.On this basis,the actual working conditions under the combined action of salt-water-temperature-ultraviolet light in the highland area were simulated,and the coupling aging characteristics of asphalt materials were studied by ultraviolet aging and dynamic mechanical analysis(DMA).The results show that the inclusion of chloride salt and sulfate makes the asphalt binder harden.Compared with the matrix asphalt,the different types of salt-incorporated asphalt cement increase with age,the creep rate decreases,and the low-temperature rheological properties continue to deteriorate.After 120 days of age,the contact angle of asphalt increased significantly,and the adhesion of salt-mixed asphalt cement decreased.Salt solution soaking and freeze-thaw cycles cause different degrees of damage to asphalt binder properties;the incorporation of rubber powder can effectively improve the temperature sensitivity of asphalt binders under salt-freezing cycle conditions.After UV aging,the matrix asphalt tends to be in a non-viscous toughness state;under the conditions of "internal etch" and "outer eclipse",the presence of salt causes the storage modulus and loss modulus of the asphalt cement to decrease and the rheological properties to decrease.During the test period,the effect of salt on the performance of asphalt is mainly physical,and the dissolution of salt particles and the effect of salt aging are the main causes of the deterioration of asphalt binder properties.The research results can provide a useful reference for design optimization and durability prediction of asphalt mixture material composition in salt-rich areas.