Preparation and characterization of active rejuvenated SBS modified bitumen for the sustainable development of high-grade asphalt pavement

Abstract

To fully restore the performance of waste SBS modified asphalt mixture, better realize its recycling and application in high-grade pavement, achieve the concept of sustainable green development of asphalt pavement. In this paper, the synergistic effects of bio-rejuvenator and active isocyanate rejuvenators (including hexamethylene diisocyanate (HDI), diphenyl-methane-diisocyanate (MDI) and toluene-2, 6-diisocyanate (TDI)) on the chemical structure, physical and rheological properties of aged SBS modified bitumen were thoroughly investigated. Fourier infrared spectrum and Gel permeation chromatography analysis indicate the isocyanate groups of active rejuvenators react with hydroxyl or carboxyl group from the degraded SBS segments to form new amide groups that can reconnect the broken segments of aged SBS and partly restore its molecular weight distribution. From physical and rheological properties, bio-rejuvenator can restore the low-temperature properties by rebalancing the colloidal structure of aged binder, meanwhile, active rejuvenators can greatly improve the high-temperature performance of rejuvenated SBS modified bitumen with bio-rejuvenator through reconnecting the broken segments of aged modifier SBS. Furthermore, MDI with benzene ring structure is more conducive to enhancing the high temperature rutting resistance of rejuvenated SBS modified bitumen. While HDI can bring some flexible segments into the restored structure of SBS, which is more beneficial to improve its low-temperature cracking resistance of rejuvenated binder. And the fluorescence images further demonstrate isocyanate rejuvenators can partly restore the crosslinking network structure of aged modifier SBS in rejuvenated SBS modified bitumen. This research would be conductive to promoting the application of rejuvenated SBS modified bitumen into the construction of high standard pavement.