Waste cooking oil potential as a green rejuvenator to restore the aged binder properties in reclaimed asphalt pavement: A state-of-the-art review

Reclaimed asphalt pavement (RAP) is a byproduct of milling flexible pavements and is typically used in recycling initiatives worldwide. The excessive dosage of RAP can have negative effects on asphalt mixture properties unless it goes through a rejuvenation process. Waste cooking oil (WCO) is one of the green solutions for rejuvenating aged binder in asphaltic concrete, and, like virgin asphalt binder, it contains light oil components. This review article offers current information on WCO's rejuvenating performance and the effect of its variable dosage on binders of varying grades. Several physical and rheological characteristics were investigated, and an appropriate spectrum of reported data was defined for the virgin and rejuvenated binders to ascertain the distinctive characteristics. Additionally, the effect of WCO on binders' asphaltene content, molecular structure, microscopic morphology, mechanical properties, and aging indices was discussed. In the high point of this review, a data range is developed for rejuvenated aged binders based on different properties prior to making a better prediction under different circumstances. Moreover, an optimum value is discussed suggesting the best balance between fatigue performance and rutting resistance. The aged binders modified with WCO exhibit better microchemical properties and particle orientation, with enhanced surface area and coating with aggregates, imitating the micropattern of conventional asphalt binder. Moreover, this review further discusses the economic and ecological aspects of WCO usage as a green asphalt binder rejuvenator.