Towards Net-Zero Asphalt Concrete: The Utilization of a Multiscale Experiment and Simulation Approach to Develop Truly Rejuvenating and Anti-Oxidative Additives for the Further Improvement of Reclaimed Asphalt Pavement

• Applicant: Professor Dr.-Ing. Pengfei Liu, Ph.D.
• Subject Area: Construction Material Sciences, Chemistry, Building Physics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 528307766

One of the major consensuses reached during the 2021 United Nations Climate Change Conference is to reduce global carbon emissions by 45% until 2030. The overarching change needed to achieve this aim is the transition from a linear towards a circular economy. One of the most potent practices incorporating this concept in roadway engineering is the increased usage of reclaimed asphalt pavement (RAP). Its widespread use could, e.g., reduce the depletion of aggregate resources, lessen the dependency on non-renewable resources, and decrease the accumulation of RAP in landfills. However, the inferior performance of RAP due to bitumen oxidation has put limits to an extensive RAP utilization. During the reprocessing of RAP, the rejuvenating agent is supposed to restore the deteriorated properties of RAP on a chemical and physical level. Finding a truly rejuvenating agent for RAP is key to net-zero asphalt concrete. The TRUE rejuvenator developed during this research is expected to further enhance the anti-oxidative durability of recycled asphalt concrete (RAC). Currently, most commercial rejuvenators are produced by using non-renewable, petroleum-based materials. Additionally, most rejuvenators only focus on restoring the viscosity of the reclaimed asphalt binder (RAB), which is done by introducing a light molecular weight compound (softener). However, the problem of the nano-aggregation of the large molecular weight fraction (asphaltene) is neglected. Therefore, it seems urgent to develop a rejuvenating agent based on sustainable resources that can soften, deagglomerate, and enhance the anti-oxidative performance of the RAB. This study aims to develop a bio-rejuvenator derived from black liquor, waste of the pulp and paper industry, and waste cooking oil (WCO), that can truly restore the physico-chemical characteristics of RAB and further enhance its anti-oxidative properties. The construction process and rejuvenating mechanisms of a bio-rejuvenator based on lignin-waste cooking oil (LWC) will be investigated with the help of multiscale experimental characterization and numerical simulation. It is expected that the LWC bio-rejuvenator can truly restore the aged bitumen properties by deagglomerating the large molecular weight fraction, by restoring the low molecular weight fraction, and by disrupting the oxidation chain reaction. Additionally, the LWC bio-rejuvenator can sequester carbon from black liquor waste and WCO, which is a carbon negative process. Furthermore, the results of this study hint towards the possibility of a true restoration of the performance of RAC, which incorporates a high degree of RAP contents, through understanding the fundamental aging and rejuvenating mechanisms of bitumen. This could substantially decrease the carbon footprint of asphalt concrete and help to achieve the large-scale goal of a net-zero emission pavement infrastructure in the future.

• DFG Programme: Research Grants
• International Connection: Taiwan
• Partner Organisation: National Science and Technology Council (NSTC)
• Cooperation Partner: Professor Shih-Hsien Sam Yang, Ph.D.