Study On Micro-characteristics And Mixture Performance Of Hot Mixed Epoxy Asphalt

In recent years,epoxy asphalt（EA）has become a hot material for special pavement.It is widely used in the field of long-span steel deck pavement because of its excellent mechanical properties,high temperature resistance and damage resistance.However,the raw materials of epoxy asphalt are obtained from petroleum products through complex processes,which are non renewable and expensive.The promotion to small and medium-sized bridges and high-grade highways is limited.In this paper,a kind of hot mixed epoxy asphalt is selected,and its performance change law is studied by changing the mixing ratio of epoxy resin（EP）and asphalt.Under the condition of meeting the basic performance of epoxy asphalt,the low content limit of epoxy resin is optimized.Through a series of micro and mixture tests,the macro performance,micro morphology,curing characteristics and mixture road performance of low content EA were tested and verified.Firstly,KD-HDP epoxy resin main agent,curing agent and 70#matrix asphalt were selected as raw materials to prepare hot mix epoxy asphalt with different EP content at the temperature of 160-165℃.The tensile test and rotational viscosity test show that the tensile strength and viscosity of epoxy asphalt increase with the increase of EP content,and the elongation at break decreases with the increase of EP content.The content of EP reaches 40%or more,which meets the requirements of mechanical properties.Fourier transform infrared spectroscopy（FTIR）test shows that the curing reaction of epoxy asphalt is mainly completed in the first 24 hours,and the overall curing degree of 75%can be completed in this stage.Detailed analysis is made between 30%and 40%EP content with sudden change in mechanical properties.The test results show that the epoxy asphalt with EP content of more than 36%meets the performance requirements of steel bridge deck pavement.Secondly,based on the optimal design of EP content,the appropriate micro morphology and modification mechanism of EP low content epoxy asphalt are explored through a series of high-precision micro tests.Fluorescence microscopy（LSCM）test shows that the two-phase transition of epoxy asphalt occurs between 32%and 34%EP content,and the proportion of fluorescence area of epoxy asphalt increases with the increase of EP content;FTIR test shows that the curing reaction rate of epoxy asphalt decreases with time,and the curing degree decreases with the increase of EP content at 24h;Atomic force microscope（AFM）test shows that the surface roughness of epoxy asphalt increases with the increase of EP content;The results of scanning electron microscope（SEM）test show that the tensile fracture interface of epoxy asphalt is more serious with the increase of EP content.The variation law of micro characteristics and mechanical properties of epoxy asphalt with different EP content are mutually confirmed.Then,combined with a series of indoor and outdoor tests to study the road performance of EP low content hot mix epoxy asphalt mixture,it is determined that the optimal asphalt aggregate ratio of epoxy asphalt EA10 graded mixture is 6.5%.The strength,high and low temperature performance,water stability,dynamic modulus and anti sliding performance of EAM were tested under conventional and limit conditions.The test results show that the stability of EAM with 34%or more EP content is greater than 40k N and has good strength;EAM with 38%or less EP content has good low-temperature deformation resistance,and the maximum bending strain of EAM with 40%EP content is 2803με,Low temperature performance is fragile;The mixture with epoxy content between 30%and 40%has good high temperature stability,water stability and skid resistance.EAM in the range of low content of target epoxy resin has good high temperature stability,water stability and anti sliding performance,and its performance gradually improves with the increase of EP content.Finally,the curing degree,fluorescence area ratio,roughness and other micro indicators of EA are selected to compare with the curing degree,strength,dynamic stability,immersion residual stability(M_RS)and freeze-thaw splitting strength ratio（TSR）of EAM,and the micro characteristics of epoxy asphalt and mixture performance are quantitatively analyzed to study the correlation between them.The analysis results show that the regularity of EA stability and EAM stability,EA fluorescence area ratio and EAM strength and dynamic stability,EA surface roughness and EAM water stability are relatively consistent,and the micro properties and macro properties of hot mixed epoxy asphalt have a good correlation.