| With the highway construction in Western China entering a high-quality development stage,the service life of asphalt pavement has been put forward more stringent requirements.However,the traditional asphalt pavement has difficulty to bear the burden due to the severe weather such as strong ultraviolet radiation,long sunshine time and the consideration of future traffic flow in Western China.Under the effect of ultraviolet radiation,it will accelerate the formation of asphalt pavement cracks,ruts and other diseases,thus reducing the durability of asphalt pavement.Therefore,it is of great significance to seek the modified materials with anti ultraviolet aging potential,carry out the research on the effect of ultraviolet aging behavior of asphalt,and realize the regulation of ultraviolet aging behavior of asphalt,so as to improve the service life of road.Aiming at the deterioration of asphalt pavement performance caused by ultraviolet aging,in this paper,two light stabilizers,Tinuvin770(T770)and Tinuvin622(T622),Polyamide 6(PA6)and Acrylate-Styrene-Acrylonitrile(ASA)were selected as the research objects,the modified asphalt was prepared from the base asphalt(70# asphalt)by aging modification process,and the influence of asphalt on basic properties and viscosity were studied.By summarizing and analyzing the existing ultraviolet aging test methods,the conversion formula of aging time and the light source,the conversion of aging time and the type of light source are determined,the indoor aging environment is constructed,and the influence of ultraviolet aging on the basic properties and rheological properties of different delayed aging modified asphalt is studied.By summarizing the preparation methods of asphalt aging film specimens,the improved asphalt film and key parameters are proposed,the surface special structure and roughness of asphalt films are analyzed and characterized by Atomic Force Microscope(AFM).Based on the technical indexes of asphalt mixture raw materials,the mix proportion design of the delayed aging modified asphalt mixture were carried out,the high anti-rutting performance and water stability performance of delayed aging modified asphalt mixture was studied,and the anti-aging performance of asphalt mixture was evaluated.The main conclusions are as follows:(1)The results show that the penetration and ductility of asphalt can be increased by four kinds of delayed aging modifiers,while the softening point of asphalt can be decreased by adding T622 light stabilizer.The improvement degree of PA6 and ASA polymers on asphalt performance is slightly lower than that of light stabilizers.Through comprehensive analysis of the influence of delayed aging modifiers on asphalt performance,the recommended dosage of T770 and T622 light stabilizers is 0.4%～0.6%,and the recommended dosages of PA6 polymers is 0.1%～0.2%.(2)Under the effect of ultraviolet aging,the penetration and ductility of the modified asphalt decreased,while the softening point increased.Based on the change rule of basic performance of delayed aging modified asphalt under ultraviolet aging,the optimum content of T770 and T622 light stabilizers is 0.4%,and that of PA6 polymer is 0.2%.Compared with the base asphalt,the delayed aging modified asphalt has higher elastic recovery rate at high temperature,T770 delayed aging modified asphalt has the best elastic recovery rate,while the elastic recovery of delayed aging modified asphalt at the stress level of 3.2k Pa is not obvious.(3)Under the effect of ultraviolet aging,the structure of the base asphalt changes significantly,and its aging degree is obviously improved.The UV aging degree of the delayed aging modified asphalt is lower than that of the base asphalt,while the roughness degree of T622 modified asphalt is slightly higher than that of T770 modified asphalt.Although the roughness of PA6 modified asphalt decreases to a certain extent in the middle aging period,the surface roughness of the whole UV aging period gradually increased.(4)The deformation change rate and total deformation of the base asphalt mixture are obviously higher than that of the delayed aging modified asphalt mixture,compared with the dynamic stability,the indices of deformation change rate and total deformation are more appropriate.Compared with 305 h base asphalt mixture,the dynamic stability of PA6 modified asphalt mixture increases by 28%,while the dynamic stability of T770 and t622 modified asphalt mixture increases by 23.2% and 18.7% respectively.The water stability performance of delayed aging modified asphalt mixture is better than that of the base asphalt mixture after the ultraviolet aging,the decrease of residual stability of T770,T622 and PA6 modified asphalt mixture is 19.7%,14.2% and 11.8% respectively in whole aging period,while the base asphalt mixture is 24.6%. |
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