Research progress on resource utilization of waste cooking oil in asphalt materials: A state-of-the-art review

Waste cooking oil is a renewable resource. Its reuse can effectively solve the problem of waste oil pollution. Due to its similar elemental composition and oil-based component to petroleum asphalt, waste cooking oil has received considerable attention for its potential utilization in asphalt materials. To facilitate the efficient utilization of waste cooking oil in asphalt materials, the present review collects state-of-the-art information on three resource utilization pathways of waste cooking oil as the modifier, rejuvenator and ground tire rubber pretreatment solvent. The production, physicochemical properties and refining processes of waste cooking oil are summarized. Process parameters for the application of waste cooking oil and the effects of waste cooking oil on the multi-scale properties of asphalt materials are provided for different resource utilization pathways, while the potential concerns and improvement measurements are also discussed. This review highlights that waste cooking oil as a rejuvenator to activate aged asphalt materials is the most promising resource utilization pathway. Meanwhile, waste cooking oil as a modifier to prepare bio-asphalt needs to focus on insufficient hightemperature performance. Waste cooking oil as the solvent for ground tire rubber pretreatment is still in the initial stage of exploration. Regarding the deficiencies of existing research on the resource utilization of waste cooking oil in asphalt materials, future work could be carried out in the following aspects: establishing the complete and standardized waste cooking oil recovery and refining process; focusing on the application of waste cooking oil in combination with additives in a flexible manner to maintain the acceptable high-temperature performance of asphalt materials; exploring the secondary aging of asphalt materials with waste cooking oil; further investigating the process, mechanism, and products application of ground tire rubber pyrolysis with waste cooking oil.