Repurposing waste oils into cleaner aged asphalt pavement materials: A critical review

Abstract

The current practice of recycled waste oil mainly includes waste cooking oil (WCO) and waste engine oil (WEO), etc. This paper provides a comprehensive and in-depth review of the current state and the feasibility of turning these oils into cleaner asphalt pavement materials. The latest types and sources of WCO and WEO in recent years were summarized and analyzed. Furthermore, two kinds of rejuvenated asphalt were sampled, after which they were used to analyze and evaluate the basic properties, rheological properties, microscopic morphology and the mechanism of aged asphalt rejuvenation. Subsequent results revealed that both WCO and WEO could restore the basic performance of aged asphalt, returning it to its original state. In addition, rejuvenated asphalt containing WCO or WEO showed excellent low temperature performance. Though the high-temperature performance of the aged asphalt could be restored with optimum oil content, the recovery was unsatisfactory. Moreover, it was observed that the high quantity of light components presents in the WCO and WEO was the key factor responsible for aged asphalt rejuvenation. Additional research is needed to fully understand the effects of the various waste oils on the performance of aged asphalt. Based on the current situation of single rejuvenator with either WCO or WEO, a compound rejuvenator with WCO and WEO is proposed to better recover waste oils, produce cleaner asphalt rejuvenators, and more effectively reduce environmental pressure. Further study is also needed to improve the compatibility between the compound rejuvenator and aged asphalt. Ultimately, the capability of recycling waste oils into aged asphalt would help minimize water and land pollution, reduce dependence on nonrenewable resources, and diversify asphalt pavement recycling options.