Rheological and Microstructural Investigation of the Effects of Rejuvenators on Reclaimed Asphalt Pavement Bitumen by DSR and AFM

Utilization of RAP in asphalt pavements may lead to severe quality problems, mostly due to asphalt aging phenomenon. Within the scope of this study, the use of rejuvenators to improve the properties of RAP is investigated. Two different types of waste oils together with a commercial rejuvenator are used. The rejuvenated bitumen samples are evaluated from both rheological and microstructural aspects. In addition, mixture testing also employed to investigate the effectiveness of used rejuvenators. Experimental studies on bitumen samples included conventional and Dynamic Shear Rheometer (DSR) testing and Atomic Force Microscopy (AFM) imagings. The results unveiled that, the utilization of rejuvenators can significantly improve the quality of recycled asphalt and threatened the aged bitumen quality. Missing bee-structures of aged bitumen samples evolve in a different type of surface topography while the mixtures performance evolves in terms of workability. The rejuvenation process provides viscous behavior to aged bitumen. The Rejuvenation Index (RI) which is a dimensionless value, simply evolves this fact. While the RI of the non-rejuvenated aged bitumen is taken as 1 (one) as per RI definition, the neat bitumen RI is calculated as 0.79, the RI of waste oils are calculated as 0.74 and 0.79 while the commercial sample RI is calculated as 0.60. Among the rejuvenators, waste oils showed similar results with almost same volume of peri- and para-phase since the commercial rejuvenator behaved more similar to neat bitumen. The rejuvenated samples workability performance improves using rejuvenating additives. Binder and mixture testing demonstrated high consistency and conformity with each other in terms of performance and aging characteristics. The results proved that, waste oils can be used as rejuvenating agents within RAP. Rejuvenators can significantly restore the properties of aged RAP bitumen and increase the amount of RAP in bituminous mixtures.