Cross-scale Structure-activity Relationship (SAR) Investigation of Interactive Behavior Between Warm-mix Polyurethane-modified Asphalt and Reclaimed Asphalt Pavement (RAP) towards a Durable and Low-carbon Paving Material

Description

The utilization of reclaimed aggregate pavement (RAP) in the asphalt mixture production process is proven as an effective approach to reducing the environmental contamination of pavement material disposal. However, various concerns have been raised about the durability of asphalt mixtures containing high RAP contents including fatigue damage, low-temperature cracking, and moisture susceptibility. Polyurethane (PU) has been extensively investigated as a sustainable reactive bitumen modifier to confer pavement materials with both superior engineering performance and environmentally beneficial qualities, which exhibits a great potential to compensate for the performance shortcomings of RAP. However, the interactive behaviour between PUmodified bitumen (PUB) and RAP has not been fundamentally understood. The main challenge to achieving this understanding is the peculiarity of PU when chemically reacting with aged bitumen and aggregates from RAP. The adhesion between PUB and RAP is sensitive to the chemistry of the components, the morphology of the interface, and the environmental and loading conditions. Hence, it is vital to investigate the adhesion between PUB and RAP to fully understand the modification mechanism and dynamic response of PU-modified aged asphalt mixture (PUAAM) containing RAP.To fill this gap in scientific understanding and to further the application of PUAAM as a durable and sustainable pavement material in Hong Kong, this project will identify the key factors affecting, and develop a cross-scale analysis framework to elucidate, the PUB–RAP interfacial adhesion.To achieve this objective, the reactive interface modification mechanism of PUMB will first be studied, and the adhesion of PUB with RAP of different mineralogy will be evaluated under various environmental and loading conditions. An upscaling combination of experimental characterizations, adhesion theories, and modelling will be applied to fundamentally understand the interactive behaviour between PUB and RAP at the binder-, mastic- and mixture-scales. Finally, all of the effects from different scales will be incorporated into a cross-scale SAR analysis system for evaluating and predicting the overall material response of interactive behaviour between the PUB and RAP, which will improve the material design and performance of PUAAM. It is expected that the outcomes of this study will enhance the sustainability of road networks both locally and worldwide in terms of maximizing the circularity of recycled wastes while minimizing GHG emissions and maintenance costs.