Sustainable cold recycled pavements: performance, leaching behavior, and life cycle assessment

Sustainable transportation demands resilient infrastructure. While cold in-place recycling (CIR) lowers emissions, moisture susceptibility compromises long-term durability. Existing research rarely integrates micro-scale thermodynamics of alternative fillers with macro-scale lifecycle environmental assessments. To bridge this gap, this study evaluates the thermodynamic, mechanical, and environmental performance of CIR mixtures incorporating steel slag (SS) and rice husk ash (RHA) using surface free energy (SFE), dynamic modulus, contaminant leaching, and life cycle assessment (LCA). Results indicate optimal substitutions (75% SS and 50% RHA) provide favorable multi-scale improvements. For SS-75, SFE increased by 49%, yielding a suitable moisture resistance with a Tensile Strength Ratio (TSR) of 88.97%, while dynamic modulus improved. This structural enhancement permits thinner virgin asphalt overlays, ensuring safe contaminant encapsulation. Consequently, SS-75 reduced global warming potential by 15.2%, energy demand by 16.6%, acidification by 16.2%, and ozone depletion by 12.8%. These findings offer generalizable evidence for environmentally optimized pavement management.