Waste Materials as Rejuvenator—A Review

Asphalt binder is used to build approximately 80% of roads worldwide in the form of flexible pavement. Many flexible pavements collapse due to surface distress such as potholes, rutting, alligator cracking, raveling, and so on, and a significant amount of maintenance work is required to address these pavement stresses. To reduce building costs, it is required to recycle asphalt pavement. The best method to preserve natural resources and minimize maintenance costs in the building industry is to use recycled asphalt pavement (RAP). However, from the literature review, it has been found that RAP is too stiff when compared to virgin binders, so different oils as a rejuvenator can be added to reduce the stiffness. Consequently, WCO (waste cooking oil) and WEO (waste engine oil) are used to improve the quality of old asphalt. This review paper included an overview of numerous studies on the WEO- and WCO-based rejuvenation of aged asphalt. It has been discovered that using WEO and WCO to rejuvenate asphalt has both positive and negative effects and the WCO produces superior results than the WEO.