Advanced thermochemical characterization and environmental assessment of modified asphalt-rubber incorporated with industrial wastes: A novel strategy to promote circular economy in sustainable road construction

The major objective of this study was to comprehensively assess the compatibility of industrial waste materials such as fly ash, pond ash, silica fume, blast furnace slags, silica fume, and mill scale slags with crumb rubber (CR) through advanced thermochemical characterization techniques and estimate the lifecycle assessment (LCA) indicators of the industrial wastes-modified modified asphalt-rubber (MAR) products. Physiochemical characterization results indicated that industrial wastes indeed contained siliceous and aliphatic organohalogen compounds, indicative of significant likelihood to react with electrophile compounds present in CR, rendering them compatible for use in the MAR-composite matrix. Thermochemical characterization confirmed the existence of specific chemical bonds and functional groups in the industrial raw materials to comfortably synthesize MAR products, further verifying the activation of CR inclusions to serve as best materials for replacement of fine natural aggregates in sustainable roadway construction. Interestingly, the rate of weight loss for CR was higher (40-80 %) than MAR products in the range of 260 to 500 degrees C, which underlined that industrial-wastes-based MAR would be more thermally stable until 500 degrees C, thereby broadening the chances of storing them even at higher temperatures. A cradle-to-gate LCA covering industrial-wastes-based MAR products and eighteen environmental impact factors recognized that efforts to optimize the key contributors will certainly help enhance the overall sustainability of the MAR product development process in the future. Overall, this first-of-its-kind study advanced the scientific understanding of compatibility and material performance of several industrial waste materials during MAR production along with helping the pavement material industry to move towards more sustainable and environmentally friendly practices through promoting circular economy and waste-to-wealth concepts.