Investigation on targeted composite rejuvenation of aged SBS-modified bitumen for low-cost and efficient recycling

Abstract

This dual regeneration method of replenishing the light component while repairing the fractured SBS structure can efficiently regenerate aged SBS-modified bitumen (SBSMB). A targeted composite regenerant consisting of bisphenol a novolac epoxy resin (bis-ANER) and colza oil bio-bitumen (COB) was proposed in this research. In addition, three catalysts with different types, N, N-Dimethylbenzylamine (BDMA), boron trifluoride-monoethylamine complex (BF₃-400), and maleic anhydride (MA) were chosen to open the epoxy ring of bis-ANER. The catalytic effect of different catalysts and rejuvenation mechanism were firstly investigated through the physical and rheological properties and the functional group characteristics of the short-term aged SBSMB recycled by various regeneration systems. The optimum dosages of COB and bis-ANER were subsequently determined in accordance with the comprehensive performance of the long-term aged SBSMB regenerated by COB and composite regenerants with optimal catalyst. The fatigue life and microscopic morphology of composite regenerated SBSMB were also tested. The results show that in comparison to BDMA and MA, BF₃-400 is more efficient in promoting the molecule repair effect of bis-ANER. SBS cross-linked structure requires ample light components for repair, and the reconstructed structure can simultaneously recover the low-temperature deformation capacity as well as the high-temperature stability of the aged SBSMB. Moreover, the physical and rheological characteristics and fatigue damage resistance of aged SBSMB were significantly improved by the “COB + bis-ANER + BF₃-400” regeneration system. Taking into account the low- and high-temperature performance of the rejuvenated SBSMB and the repair situation of SBS molecular structure, the optimal dosages of COB and bis-ANER were determined to be 8% and 1.5%, wherein excessive bis-ANER will cause a negative influence on low-temperature performance. Finally, fluorescence pictures further verified the connection effect of the composite rejuvenators on SBS short chains.