Study On Microscopic Characteristics And Performance Of Asphalt Under Sulfate Erosion

Salt lakes and saline soil areas in western my country,sulfates enriched in the natural environment enter the interior of the asphalt pavement structure due to seepage,temperature gradient,capillary water rise,etc.It greatly shortens the service life of the asphalt pavement.As the bonding material in asphalt mixture,its own properties directly determine the road performance of asphalt pavement.Therefore,it is of great significance to carry out the research on the performance of asphalt in the environment of salt erosion.In this paper,according to the characteristics of the actual engineering environment of asphalt pavement in the salt lake and saline soil areas in western my country,an indoor salt erosion test is designed by itself,and the microscopic characteristics and performance of asphalt under the action of sulfate erosion are studied.Four-component,infrared spectroscopy,thermogravimetric,three major indexes and Brookfield viscosity tests were used to study the changing laws of the microscopic properties and basic properties of asphalt under the action of sulfate erosion.The results show that under the action of sulfate erosion,the content of asphaltenes in asphalt increases,the content of saturate,aromatic and colloid decreases,the colloid type of asphalt gradually changes to gel type,and the stability of colloid structure decreases.Asphalt will undergo oxidative aging in water and Na2SO4 solution to generate carbonyl and sulfoxide-based substances,and sulfate attack can accelerate the aging of asphalt.With the increase of the Na2SO4 solution concentration,the initial weight loss temperature and the maximum weight loss rate temperature of the asphalt gradually increased,the mass loss rate gradually decreased,and the thermal stability of the asphalt gradually became better.The corresponding macroscopic performance is that the penetration and ductility of asphalt decrease,the softening point and Brookfield viscosity increase,the deformation resistance and high temperature stability of asphalt increase,and the low temperature crack resistance decreases.The rheological properties of asphalt under sulfate attack were studied by DSR,MSCR and BBR tests.The results show that the erosion effect of sulfate on asphalt is a process that increases the elastic component of asphalt and reduces the viscous component.Under the condition of salt-dry-wet cycle,with the increase of Na2SO4 solution concentration and the increase of the number of dry-wet cycles,the anti-rutting ability and elastic recovery ability of asphalt are enhanced,but the low-temperature ductility and stress relaxation ability decrease.Based on the surface free energy theory,the adhesion between asphalt and aggregate under the action of sulfate erosion was deeply studied and analyzed.The results show that with the increase of the concentration of Na2SO4 solution and the increase of the number of drying and wetting cycles,the adhesion work between asphalt and aggregate decreases,the exfoliation work increases,the adhesion performance between asphalt and aggregate decreases,and the water damage resistance becomes worse.Through the analysis of the test results of the indoor boiled spalling rate,it is found that the results are completely consistent with the results of the surface free energy test,indicating that the surface free energy theory can better evaluate the adhesion between asphalt and aggregates.