Comparative life cycle assessment of three types of crumb rubber modified asphalt under different system boundaries

Abstract

This study employs a life cycle assessment (LCA) to quantify the environmental impacts of three crumb rubber recycling technologies in asphalt rubber (AR) mixtures: wet, dry, and terminal blend. The analysis identifies key factors affecting their environmental performance across the life cycle. Results were characterized into climate change, stratospheric ozone depletion, fine particulate matter, terrestrial acidification, marine eutrophication, freshwater ecotoxicity, human toxicity, and Land use. Dynamic rankings of the three AR technologies along their life cycle stages in each impact category would enable identification of the influencing factors and provide reference for the further improvement. This study reveals that dry technology is likely to have the most significant environmental impacts across all categories (51.85 %-100 %), whereas terminal blended technology generally presents the lowest impact (51.85 %-88.89 %), with the exception of freshwater ecotoxicity (33.33 %) and human toxicity (22.22 %), where wet technology shows the least impact. The analysis underscores the importance of asphalt mixture designs, with appropriate binder content, potential reduction in surface course thickness, and reduced maintenance frequency, as strategies to enhance the environmental performance of AR technologies. The study concludes that the environmental performance of AR pavement is highly dependent on their in-service durability, with scenario-based analysis indicating that adequate durability ensures environmental effectiveness.