| Asphalt pavement will produce various diseases under the action of traffic load and natural factors.In order to ensure the performance of asphalt pavement needs to be maintained or even overhauled,resulting in a large number of waste asphalt mixture.Recycling of waste asphalt mixture is an effective way to realize the sustainable development of asphalt pavement.SBS modified asphalt is often used in the middle and upper layers of asphalt pavement,so most of the waste materials produced by maintenance and milling of asphalt pavement surface are SBS modified asphalt mixture.The basis of asphalt mixture recycling is asphalt aging mechanism and aging degree evaluation.In this paper,the aging mechanism of SBS modified asphalt under thermo-photo-oxygen coupling aging condition was studied by using self-developed thermo-photo-oxygen coupling aging test equipment.Based on the extensive analysis of the literature at home and abroad,the thermo-photo-oxidative coupling aging at 70℃,100℃,135℃ and 100W/m2 ultraviolet radiation intensity,and the comparative tests of 135℃ adiabatic aging and 135℃thermo-oxidative aging were carried out.The softening point,composition,DSR rheological properties and infrared spectroscopy(FTIR)tests of SBS modified asphalt before and after aging were carried out.The aging law of SBS modified asphalt under different coupling aging was analyzed.The coupling aging prediction equation of softening point,colloid instability index,anti-rutting factor and comprehensive aging index was proposed.The correlation of each test index was analyzed by grey system theory.The analysis of softening point and component test results of SBS modified asphalt under the thermo-photo-oxidative coupling aging showed that the thermo-oxidative effect was the main factor of aging(the average contribution rate was 60.6%),and the UV effect gradually decreased with aging time,with the average contribution rate of 24.6%and the softening point and colloidal instability index increase in power function with aging time,and increase linearly with aging temperature.a+b·tc(a,b,c are regression parameters)can be used as the prediction equation of softening point and colloidal instability index of SBS modified asphalt under thermo-photo-oxygen coupling aging condition,and the correlation coefficient R2 is above 98%.DSR rheological test results show that the complex shear modulus G*and anti-rutting factor G*/sin(δ)decrease and tend to be gentle with the increase of test temperature,and increase exponentially with aging time,and the change of phase angle δ is complex.The increase ratio of anti-rutting factor RI analysis shows that the aging temperature has a great influence on the thermo-photo-oxidative coupling aging.The increase ratio of anti-rutting factor RI analysis shows that the aging temperature has a great influence on the thermo-photo-oxidative coupling aging of SBS modified asphalt.The prediction equation of reaction rate and anti-rutting factor growth ratio RI(fitting parameters R2>94%)can be established based on Arrhenius aging kinetics model.The results of FTIR analysis show that the comprehensive aging index(CAI)can well characterize the aging degree of SBS modified asphalt,and the prediction equation of comprehensive aging index(CAI)with aging temperature and time can be established based on Verhulst model,and the grading standard of SBS modified asphalt aging degree is proposed.The results’ of grey system theory analysis show that the microscopic analysis index and macroscopic performance index of SBS modified asphalt have good correlation under thermo-photo-oxygen coupling aging,and ultraviolet ray is the main factor causing the migration and modification of light components in matrix asphalt and the oxidation degradation of SBS modifier,and the high temperature thermo-oxygen factor accelerates the reaction rate of each component. |
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