Investigating bitumen rejuvenation mechanisms using a coupled rheometry-morphology characterization approach

The reuse of oxidized bitumen offers a viable solution to enhancing pavements’ sustainability and reducing consumption of virgin bitumen. As such use of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) containing approximately 5 and 20% bitumen, respectively has been promoted by both road authorities and the pavement industry. However, due to highly oxidized nature of aforementioned bitumen, its incorporation into new asphalt pavements can negatively impact their performance and lead to premature cracking. Therefore, restoring properties of oxidized bitumen is critical to render it as a viable source. This in turn, poses an intriguing scientific inquiry pertaining the definition and means of restoration. This paper defines a chemo-mechanical metrics for measuring extent of restoration while demonstrating the use of a bio-oil produced from swine manure as a cost-effective additive for rejuvenating aged bitumen. Bitumen used in this study includes both laboratory-aged bitumen and those extracted directly from field recovered samples. Characterization of the aged bitumen before and after rejuvenation was conducted by Rheometry, and Atomic Force Microscopy (AFM). The results of experiments showed that addition of aforementioned bio-oil referred to as bio-rejuvenator (BR) in this study significantly restored bitumen properties. In addition, correlation between size of morphological features referred to as “bees” and rheological properties suggests that “bee” length has a moderating effect on the relationship between bitumen's stiffness and viscosity.