Rejuvenation of recycled asphalt pavement using oily sludge: Advancing circular economy in pavement recycling

The incorporation of reclaimed asphalt pavement (RAP) into new pavements aids in conserving petroleum asphalt and mineral resources. However, higher RAP proportion can lead to performance issues, which makes the use of rejuvenators necessary. This study investigated the effectiveness of oily sludge (OS) as a rejuvenator for high RAP content through a series of binder characterizations and evaluation of asphalt mixture engineering properties. Rheological parameters of binders at different temperatures, OS dosage and aging conditions were measured using dynamic shear rheometer. Fourier-transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) were employed to study detailed insights into the chemical composition and surface morphology of the binders. The rheological results indicated that adding OS reduced the fatigue factor up to 72.9 % compared to recycled asphalt binder and maintained the rutting resistance (PG 64) similar to conventional binder. The morphological analysis showed that incorporating OS decreased the surface roughness of recycled asphalt binder. The addition of RAP up to 90 % increased the Marshall stability by 22 % and reduced the flow values around 1 % of oily sludge recycled (OSR) mixtures. The volumetric properties of OSR mixtures up to 90 % RAP complied with the required PWD specification.