| WEA composite binder is a heterogeneous material,and its strength formation involves the complex interaction of water evaporation,particle diffusion and coalescence,curing of waterborne epoxy resin and demulsification of SBR modified emulsified asphalt,its performance changes are unpredictable.Therefore,it is necessary to conduct in-depth research on its anti-aging properties.With the help of asphalt aging test method,this paper discusses the decay law of thermal oxidation aging,ultraviolet aging and natural aging performance of composite binder,and then determines its ability to resist environmental action in the actual service process.The effects of waterborne epoxy emulsion content on mechanical properties,high and low temperature performance and microstructure of WEA composite cementing material were investigated by adhesion pull test,dynamic shear rheology test,low temperature ductility test,infrared spectroscopy technology and fluorescence microscopy analysis.The results showed that the adhesive strength,high temperature stability and deformation recovery ability of the composite cementing material were improved by adding waterborne epoxy emulsion,while the plasticity at low temperature decreased,but still met the requirements of the specification.The characteristic peaks of each component remain in the composite binder,and the hardening process is the interaction of curing of waterborne epoxy resin and demulsification of SBR modified emulsified asphalt,including physical and chemical crosslinking,with the content of the waterborne epoxy emulsion increased,the structure of epoxy resin was changed from granular to island like in the composite system.In this paper,RTFOT,60℃,80℃,100℃thermal oxygen aging,UV aging and natural exposure aging were used to aging the composite binder,and based on three indexes,viscosity,elastic recovery,temperature scanning,frequency scanning and stress creep recovery test,the change rules of physical properties and rheological properties after different aging methods were studied.The results showed that with the increase of aging time and temperature,the aging resistance of composite binder decreased,and the aging rate decreased with the increase of waterborne epoxy emulsion content.Compared with SBR modified emulsified asphalt,the penetration ratio of WEA composite cementation increased,the viscosity aging index and complex modulus aging index decreased,the phase angle aging index increased,the change of anti-rutting factor with temperature is small,the creep recovery rate increases,and the irrecoverable creep compliance decreases.This indicates that the incorporation of waterborne epoxy emulsion can retard the aging process of composite cementing material,enhance its anti-aging performance,and improve the temperature sensitivity,high temperature stability and elastic recovery performance of cementing material.The change of macro properties of composite binder after aging is the external manifestation of microstructure transformation.In this paper,the chemical structure and micro morphology of composite binder after aging were characterized by infrared spectroscopy and fluorescence microscope.The results showed that during the aging process,the chemical structure changes of the binder were mainly reflected in the enhancement of the absorption peaks of carbonyl and sulfoxide groups and the weakening of the absorption peaks of butadiene groups,while the absorption peaks of epoxy resin first enhance and then weaken,indicating that the curing reaction of residual waterborne epoxy resin occurs at the initial stage of aging.Compared with SBR emulsified asphalt,the aging index of IC=O and IS=O increased and the IC=Caging index decreased of WEA composite binder,indicating that waterborne epoxy emulsion can inhibit the formation of oxygen functional groups and the fracture of unsaturated double bonds to some extent.The composition distribution showed that the number of fluorescent particles,size and particle aggregation decreased significantly in the fluorescence image of the aged composite binder.With the deepening of aging degree,the polymer distribution was island structure,showing partial disintegration,and dispersed in the asphalt phase as particles.Under different aging conditions,there was a good linear correlation between the viscosity of composite cementation material and the aging time,the correlation was different with the dosage of waterborne epoxy emulsion and the aging condition.According to the formula,the decay law of pavement performance in actual service process can be deduced through laboratory test data of cementing material,thus providing technical support for pavement maintenance. |
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