Study On The Interfacial Adhesion Failure Behavior Of Asphalt-Aggregate Under Water-Temperature Coupling

When asphalt pavement is put into use,it often occurs with a series of diseases such as loose and pit,which is one of the major forms in the highway disease in our country at this stage.In the hot and rainy summer,water will penetrate the pavement structure through the gap,and replace with the asphalt film on the aggegate.High temperatures can exacerbate the movement of water molecules,resulting in that the asphalt strips from the aggregate more easily.For the areas that have large temperature difference between day and night,residual water in the void is prone to frost heaving pressure,which will accelerate the debonding between the asphalt and aggregate and result in a more serious water damage.Therefore,it's significant for reducing the early disease of asphalt pavement and prolonging its service life to study the effects of water-temperature coupling on the asphalt-aggregate interfacial adhesion and propose relevant technical improvement measures.First of all,combined with water boiling method and scanning electron microscope,photoelectric colormetric was used to study the effects of water-temperature coupling including hot water bath and freeze-thaw cycling on the interfacial adhesion between three types of asphalt including 70# regular asphalt,SBS modified asphalt,high viscosity asphalt and two types of aggregate including basalt and limestone,as well as explaining its failure.It is resulted that the destruction mode of the two types of effects to the interface are differ from each other.The adhesion reduces with the bath time increasing,while it shows ups and downs with the freeze-thaw cycles increasing.There is a better hydrothermal and freeze-thaw resistance for high viscosity asphalt in all.It is proved that photoelectric colorimetry can evaluate the interfacial adhesion of asphalt-aggregate under hot water bath,while it is not necessary to combine with scanning electron microscope to explain for the results of freeze-thaw cycling.Secondly,atomic force microscope was used to investigate the surface morphology and roughness of the three types of asphalt,and the aggregate was replaced with the probe to analyze the surface nanoscale adhesion.Some samples were selected to test the mechanical properties of asphalt mortar at the interface using nanoindentation technology.As shown by the datas,the bees on the surface of the asphalt scatter into tiny fragments under hot water bath,while it shows alternate changes between disappearance and reconstruction.Short-term hot water bath can improve the compatibility of modifier and regualr asphalt,while short-term freeze-thaw cyclying can enrich the surface morphology of asphalt so that it can slow down the degradation of asphalt performance to a certain extent.Under hot water bath,the modulus and hardness of the asphalt both decrease,while they increase under freeze-thaw cycling.Thirdly,the interfacial models of three types of asphalt and two types of typical oxides were established by molecular dynamics,and simple water damage was simulated.Then,kinetic simulation are performed at several common temperatures.The effect ofwater-temperature coupling on the interfacial adhesion was investigated by analyzing the interface energy and cohesive energy,and a targeted design proposal for pavement material composition was advanced.It shows that SBS modifier can improve the low temperature adhesion of asphalt,but it has poor thermal stability,which is little to improve the adhesion of asphalt at high temperature,some additives should be add to better play its role.The SBS modifier is near surface of the oxide crystal in SBS modified asphalt,while it is in the middle of the asphalt in high viscosity asphalt.It is related to the form of its role in the interfacial effects.Finally,comparing with SBS modified asphalt and high viscosity asphalt,specific mixture gradation of drainage pavement was used to test the water stability changes with basalt under the two types of water-temperature coupling.It shows that both hot water bath and freeze-thaw cycling can decrease the water stability of porous asphalt mixture,but there is no large difference for the effects.Water-soak dispersion test can better evaluate the water stability of porous asphalt mixture.For the upper layer of drainage pavement,it is recommended to use high viscosity asphalt and basalt for material composition design.