Short-term aging characteristics and mechanisms of SBS-modified bio-asphalt binder considering time-dependent effect

Bio-asphalt has emerged as a reliable material for replacing conventional asphalt in asphalt modification owing to its well social, environmental and economic benefits. However, the short-term aging mechanisms of modified bio-asphalt binders considering time-dependent effect have not been discussed widely in previous studies. In this study, considering the extensive use of SBS-modified bio-asphalt binders, the aging characteristics of an SBS-modified bio-asphalt binder (SBA) based on six different aging times (0 min, 40 min, 65 min, 130 min, 195 min, and 260 min) and four different bio-asphalt contents (0%, 3%, 6%, and 9%) are investigated using the rolling thin film oven test (RTFOT). Bio-asphalt can significantly improve the aging resistance of the SBA, although the improvement effect decreases as the bio-asphalt content increases. Moreover, the short-term aging mechanisms of the SBA considering time-dependent effect are determined based on fluorescence microscope (FM) and Fourier transform infrared spectroscopy (FTIR). The results indicate that the aging of the SBA at early stage is primarily attributed to the disintegration of the SBS cross-linked structure due to the volatilization of light components (e.g., saturates and aromatics) and the thermal-oxidative degradation of styrene-butadiene. With the increase of aging time, aging is primarily caused by the conversion of resins, saturates, and aro-matics to asphaltenes due to the oxidation of the polyunsaturated carbon chain and sulfur. Although bio-asphalt can delay the aging, it does not change the evolution process.