Research On Influence Of Reactive Rejuvenator On Properties Of Aged SBS Modified Asphalt And Its Mixture

SBS modified asphalt mixture is widely used in high grade highway for its excellent performance,but it will be aged in service.The maintenance and renovation of asphalt pavement will produce a large amount of waste SBS modified asphalt mixture,and its recycling is paramount for realizing the "dual carbon" goal in the transportation industry.SBS modified asphalt is composed of asphalt and SBS,so the key to regeneration is to restore the composition,structure and performance of asphalt and SBS.However,the existing common rejuvenators can only restore the composition and performance of aged asphalt without restoring the structure and performance of aged SBS,which leads to the limited recovery effect on the performance of aged SBS modified asphalt,and seriously reduces the recycling value of waste SBS modified asphalt mixture.In this paper,for fully restoring the performance of aged SBS modified asphalt,common rejuvenators and reactive compounds were used to restore the composition,structure and performance of aged asphalt and aged SBS separately.The effects of different types of common rejuvenators(third vacuum stream oil,corn oil and cashew nut shell oil)and different structures of isocyanate reactive compounds(hexamethylene diisocyanate,diphenylmethane diisocyanate and toluene-2,6-diisocyanate)on the properties of aged SBS modified asphalt were systematically studied.Further,the preferred common rejuvenator and reactive compounds were compounded to prepare the reactive rejuvenator.The influences of reactive rejuvenator on the structure,physical-rheological properties of aged SBS modified asphalt and its evolution with time were investigated,and the recovery effect of interface characteristics and road performance of aged SBS modified asphalt mixture after reaction regeneration was also studied.The main conclusions are as follows:(1)The composition and structure of three common rejuvenators had obviously different effects on the performance recovery of aged SBS modified asphalt.Compared with the third vacuum stream oil with non-polar saturated alkane as the main component,corn oil with polar long-chain structure and cashew nut shell oil were more conducive to improve the low-temperature performance of aged SBS modified asphalt.Cashew nut shell oil rich in polar aromatic derivatives had the best effect on improving its fatigue resistance,followed by corn oil containing polar fatty acid.Cashew nut oil with hindered phenolic structure enhanced the aging resistance of rejuvenated SBS modified asphalt,while the third vacuum stream oil and corn oil containing unsaturated double bond had adverse effects on its aging resistance.Comprehensive comparison shows that cashew nut shell oil had the best recovery effect on the performance of aged SBS modified asphalt.(2)Isocyanate reactive compounds with different structures all significantly increased the molecular weight of aged SBS and partially recover its network structure in asphalt,but there were some differences in the recovery ability of high-and low-temperature properties and anti-fatigue properties of rejuvenated SBS modified asphalt.Diphenylmethane diisocyanate and toluene-2,6-diisocyanate had better recovery effect on the high-temperature properties of rejuvenated SBS modified asphalt than hexamethylene diisocyanate.The hexamethylene diisocyanate was better than diphenylmethane diisocyanate and toluene-2,6-diisocyanate on improving the low-temperature properties of rejuvenated SBS modified asphalt.The effect of diphenylmethane diisocyanate on improving the fatigue resistance of rejuvenated SBS modified asphalt was much better than that of hexamethylene diisocyanate and toluene-2,6-diisocyanate.Comprehensive comparison shows that diphenylmethane diisocyanate had excellent recovery effect on the high-temperature performance and fatigue resistance of aged SBS modified asphalt,while hexamethylene diisocyanate had the greatest improvement effect on its low-temperature performance.(3)The reactive rejuvenator prepared by the preferred common rejuvenator(cashew nut shell oil)and two reactive compounds(diphenylmethane diisocyanate and hexamethylene diisocyanate)effectively restored the high-and low-temperature properties and fatigue resistance of aged SBS modified asphalt.The high temperature grade of aged SBS modified asphalt was maintained at PG76,the low temperature creep rate was 21.6% higher than that of aged SBS modified asphalt,and the fatigue life at 5.0% strain level was greatly increased by 94.9% after the reactive regeneration by using reactive rejuvenator to simulate the actual mixing time and temperature.The structural reconstruction reaction of reactive rejuvenated SBS modified asphalt continues still lasted for a period of time,which further improved the properties of the modified asphalt.The high temperature grade of reactive rejuvenated SBS modified asphalt increased from PG76 to PG82(restored to the initial level),the high temperature repeated creep recovery ability was greatly enhanced after 15 days at ambient temperature 25 ℃,and the low temperature creep rate was 30.7% higher than that of aged SBS modified asphalt,the fatigue life at 5.0% strain level was 188.5%higher than that of aged SBS modified asphalt.(4)The interfacial characteristics of aged SBS modified asphalt mixture were significantly improved by reactive rejuvenator,and the adhesion work and anti-peeling work between SBS modified asphalt and aggregate were greatly improved,which was attributed to the physical-chemical interactions between aggregates and reactive rejuvenator,new groups generated by regeneration reaction.The Marshall stability and dynamic stability of rejuvenated SBS modified asphalt mixture prepared with reactive rejuvenator were restored to 94.7% and 93.6% of the initial level,the maximum flexural tensile strain and flexural tensile strength at low temperature were restored to85.9% and 87.7% respectively of the initial level,the fatigue life was restored to more than 90.0% of the initial level,and the freeze-thaw splitting strength ratio were restored to 98.4% of the initial level,respectively.The high temperature properties and water stability of reactive rejuvenated SBS modified asphalt were completely restored to the initial level,its low temperature properties and fatigue resistance were further improved with the extension of time.