Effects of Novel Rejuvenators on Chemical and Rheological Properties of Aged SBS Modified Bitumen

Abstract

SBS modified bitumen is popularly utilized in road construction owing to its outstanding performance and competitive pricing. However, like normal bitumen, SBS modified bitumen will also be aged and causing asphalt pavement distress and the need for maintenance, resulting in a significant amount of wasted modified asphalt. Recycling waste asphalt is critical for lowering road construction and maintenance costs, conserving original resources, and protecting the environment. Since recycled bitumen waste deteriorates over time, rejuvenators can be used to restore its properties. Many rejuvenators, on the other hand, only rejuvenate aged bitumen, and the excellent performance of SBS modified bitumen is largely attributable to the SBS polymer and polymer network structure in it. As a necessary consequence, it is critical to consider the simultaneous rejuvenation of both aged bitumen and degraded SBS polymer. 
In this research, SBS modified bitumen was aged with thin-film oven test (TFOT), followed by pressure aging vessel (PAV), and various contents and proportions of reference rejuvenators, physical rejuvenators, and chemical rejuvenators were applied to the aged bitumen. Dynamic shear rheometer (DSR) tests and Fourier transform infrared (FTIR) tests were conducted on aged and rejuvenated bitumen samples to study rejuvenation effects with different types of oil, SBS content, and chemical compounds by comparing rheological and chemical properties. The study showed that the rejuvenation effects of pure oil based rejuvenators are intimately connected to environmental temperature and oil molecular weight. High molecular weight oil provides better rutting resistance in high temperatures and low molecular weight oil provides better cracking and fatigue resistance at low temperatures. Rejuvenated bitumen with chemical rejuvenators performed admirably at high temperatures but with poor cracking and fatigue resistance in low temperatures. Increasing the SBS content in physical rejuvenators improves rutting resistance at high temperatures and reduces cracking resistance but partially improves fatigue resistance at low temperatures. The effects of different oil types and proportions for physical rejuvenators at high temperatures are a little complicated. In rejuvenators with low or medium SBS content, increasing proportion reduces performance, indicating oil is dominant now. In rejuvenators with high SBS content, increasing proportion improves performance, implying SBS is currently leading. For rejuvenators containing rapeseed oil and high SBS content, rising proportion barely affects performance, possibly because high viscosity oil has diminished the effect of high SBS content. For low temperature performance, physical rejuvenators with large molecular weight oil have the worst performance. Furthermore, increasing physical rejuvenator proportion improves the cracking and fatigue resistance of rejuvenated bitumen. In FTIR analysis, the polybutadiene group index IPB of rejuvenated bitumen with physical rejuvenators increases significantly and continues to rise as the proportion or SBS content increases. Moreover, the IPB index increases for rejuvenated bitumen with chemical rejuvenators, and a group of new absorption peaks in the spectrum demonstrated MDI had chemical reactions with degraded SBS polymer and had successfully connected the fracture SBS polymer segment.