Balancing performance and environmental impacts of crumb rubber-modified asphalt binders using a multi-objective lifecycle optimization process

The major objective of this study was to assess the correlations of environmental impact indicators along with fundamental consistency and rheological performance of asphalt-rubber binders through multi-objective optimization of crumb rubber (CR) dosages by adopting the lifecycle assessment (LCA) approach. The scope of the effort included: (i) preparation of modified asphalt binder with three CR dosages: 10, 15, and 20% by weight of the base virgin asphalt binder, (ii) fundamental consistency tests to assess the performance of virgin and CR-modified asphalt binder blends, (iii) lifecycle inventory analysis from raw material extraction to the production of CR-modified asphalt binders, (iv) LCA of virgin and CR-modified asphalt binder blends, (v) correlation analysis of CR contents and the corresponding environmental and performance parameters, and (vi) multi-objective optimization of CR dosage to balance the performance enhancement with environmental sustainability. A reinforcement learning approach was implemented in optimizing the CR content in asphalt binder blends by balancing the environmental sustainability and performance objective, which revealed that the asphalt binder blend incorporated with 20% CR demonstrated a favorable balance between the mechanical performance and environmental impacts. It is envisioned that the framework developed in this study will support the strategic reuse of end-of-life tires in high-performance low-carbon pavement systems while also advancing the long-term goals of resource circularity in the context of sustainable infrastructure.