Study On Aging Characteristics And Mechanism Of Ultraviolet Absorber Intercalated OMMT Modified Asphalt

The thermal oxygen aging and ultraviolet(UV)aging of asphalt binders are important causes of road surface disease and insufficient durability.The addition of modifier can improve the aging resistance of asphalt.Montmorillonite(MMT)can improve the resistant of thermal oxidative aging properties of asphalt,but the addition of MMT will reduce the low temperature performances of asphalt.The apply of ultraviolet absorber(UVA)can inhibit the ultraviolet aging process of asphalt.But the heat resistance of UVA is poor,and it is easy to be failed in the process of mixing and paving of asphalt.In this paper,by intercalating UVA with organic montmorillonite(OMMT),it aims to significantly improve the thermal oxygen and UV aging resistances of asphalt and prolong the service life of asphalt pavement.Different UVA/OMMT modifiers(UV326/OMMT,UV328/OMMT,UV531/OMMT,UV770/OMMT)were prepared by organic intercalation,and the structure,ultraviolet absorption and reflectance of UVA/OMMT were characterized by X-ray diffraction test(XRD),fourier transform infrared spectroscopy(FTIR)and UV-visible spectroscopy(UV-vis).Then,five dosages(0wt%,1wt%,2wt%,3wt%,4wt%)were applied to asphalt modifying.The thermal oxygen aging and UV aging tests were performed.Physical and rheological properties tests were used to test and analyze the modified asphalt before and after aging,and the suitable dosage and species were preferred.Finally,the asphalt with the best aging resistance was subjected to fluorescence microscopy(FM),rod thin layer chromatography-hydrogen flame particle detector(TLC-FID)and FTIR test to study the effects of UVA/OMMT on the micromorphology,four components and chemical structure of asphalt under different aging stages.The mechanism of UVA/OMMT on asphalt aging performance is revealed.It is found that the interlayer spacing of UVA/OMMT is significantly enlarged after organic intercalation treatment.Four kinds of UVA and OMMT form composite materials with intercalated structure.Compared with OMMT modified asphalt,the low temperature performance of UVA/OMMT modified asphalt is improved.All UVA/OMMT can improve the thermal oxygen and UV aging properties of asphalt,and the improvement effect of UV326/OMMT and UV328/OMMT is more significant.The mechanism analysis shows that the improvement of asphalt performance by different types of UVA/OMMT is mainly affected by the layered structure,UVA characteristics and intercalation effect.The intercalation effect of UVA/OMMT plays an important role of asphalt before aging.The lower the intercalation rate,the more free UVA dispersed in asphalt,and the better the low temperature performance of modified asphalt.During the TFOT aging process,UVA/OMMT forms intercalated structure with asphalt,so the path of oxygen into the interior of asphalt is prolonged and blocked,and the thermal oxygen aging performance of asphalt is improved.The UV aging performance of asphalt is mainly affected by the UVA characteristics.A large number of UV328 and UV326 which successfully form intercalated structure with OMMT inhibit the UV aging progress by capturing free radicals and absorbing ultraviolet light in the asphalt.The UV aging resistance of the modified asphalt is significantly improved.