Effect of different structured epoxy-type reactive rejuvenators on recycling performance and repair mechanism of the aged styrene-butadiene-styrene (SBS) modified bitumen

The styrene-butadiene-styrene (SBS) modified bitumen (SMB) has gained worldwide popularity due to its exceptional performance. However, the waste SMB generated by its maintenance and resurfacing urgently needs to be rejuvenated with good performance for the prolonged service life of asphalt roads. In this study, the epoxy- type reactive rejuvenators, trimethylmethylpropane triglycidyl ether (TMPTE) and polyethylene glycol diglycidyl ether (PEGDGE), combined with vegetable oil (VO) were employed to reconstruct the aged SBS modified bitumen. Mild-moderate thermo-oxidative aging and pressure aging methods were applied, and regeneration experiments were conducted subsequently. FTIR indicates the occurrence of the SBS repair reaction or/and epoxy homo-polymerization. GPC demonstrates the restoration of characteristic peaks for both SBS and bitumen in aged SMB after the regeneration, while FM images show a reconstructed network structure of SBS. From a macroscopic perspective, the regeneration of aged SMB was assessed from four aspects, i.e. high/low temperature performance, elasticity and stiffness. It is found that the PEGDGE regenerated SMB exhibits the best high- temperature performance in the thermo-oxidative aging system, while the TMPTE regenerated SMB demonstrates the best high-temperature performance in the pressure aging system. And TMPTE regenerated SMB exhibits the best low temperature performance and elasticity in the thermo-oxidative aging system, and PEGDGE regenerated SMB exhibits the excellent low temperature performance and recovery performance in the pressure aging system. Meanwhile, in the thermo-oxidative aging system, PEGDGE regenerated SMB demonstrates superior deformation resistance. In the pressure-aging system, TMPTE regenerated SMB exhibits exceptional deformation resistance. The mechanism for the varying regeneration effects of different aging methods and regeneration systems were analyzed, suggesting a possible correlation with the molecular structures (e.g. functionality, chain flexibility) of the epoxy-type reactive rejuvenators. This study offers a theoretical guidance for regenerating aged SMB pavements with varying degrees of aging and a reference for selection or synthesis of reactive rejuvenators.