Investigation Of Emulsified Asphalt-aggregates Interface Adhesion Performance And Improvement Methods

Emulsified asphalt and aggregate interface adhesion is relatively weak,resulting in the emulsified asphalt mixture easy to loose,strip and weak resistance to moisture damage,which limit its further popularization and application in highway and high speed railway projects.Therefore,it is of great significance to carry out the research on the adhesion between emulsified asphalt and aggregate,find the method to enhance the interface adhesion,and improve the moisture damage resistance ability of emulsified asphalt mixture.In this paper,four representative emulsified bitumen were selected:emulsified matrix bitumen,emulsified SBR bitumen,emulsified SBS bitumen and emulsified SBS/SBR bitumen,and the preparation process of corresponding emulsified bitumen was determined.The influence of emulsification,modification and aging on the rheological properties of selected asphalt and its evaporation residue was investigated through rheological tests.For emulsified asphalt,by the improved boiling test,the effects of emulsification,type of stone,modifier,health preservation,aging and freeze-thaw action on asphalt-aggregate adhesion rate were analyzed,and the changing law of asphalt film on aggregate surface under boiling was explained.Aiming at the defects of the existing pull-out test,an improved pullout test was designed based on the rheometer,which was suitable for evaluating the adhesion properties of emulsified asphalt-aggregate interface.The influences of temperature,type of asphalt,thickness of asphalt film,loading rate,type of stone,health preservation and freeze-thaw action on interface adhesion strength were explored.The change rule and internal reason of interface adhesion were analyzed.Through improved boiling test and improved pull-out test,a reasonable method to enhance the adhesion of emulsified asphalt-aggregate interface was determined.Through the performance test of emulsified asphalt mixture,the actual improvement effect of the interface adhesion property enhancement method on the performance of mixture was evaluated.The main conclusions from the study include:Emulsification can be separated by the addition of emulsifier and the physical grinding effect of colloid-grinder,which have different influence on the rheological properties of matrix asphalt and SBS asphalt.The sensitivity of emulsified bitumen aggregate adhesion rate to the influencing factors is as follows:health preservation>freeze-thaw>modification>type of stone>emulsification.The change of asphalt film under the action of water temperature is related to the formation and movement of the de-adhesion line at the asphalt-aggregate interface.The existence of micro pores on the stone surface extends the moving distance of the de-adhesion line to a certain extent,and slows down the de-adhesion rate between asphalt and aggregate.It is determined that the main factors affecting the emulsified asphalt-aggregate adhesion are the moisture in the emulsified asphalt and external moisture from the environment.The relationship between interfacial adhesion strength and strain rate,test temperature and thickness of asphalt film was established,and the transition temperature of adhesion and cohesion T₀ and the ultimate interfacial strengthδ₀ were defined.The key steps in the formation of interface adhesion strength between emulsified asphalt and aggregate are clarified.Coupling treatment can not only improve the adhesion rate and adhesion interface strength between emulsified asphalt and aggregate,but also improve the durability of emulsified asphalt and aggregate interface adhesion.Compared with cement or coupling treatment alone,cement and coupling treatment work together to improve the moisture damage resistance of the mixture is better...