Performance-informed life cycle assessment of waste-derived asphalt mixtures for full aggregate replacement

Increasing the circularity of asphalt pavements through industrial by-products and reclaimed asphalt pavement (RAP) offers a practical route to reduce reliance on virgin aggregates and the associated upstream burdens. This study presents an integrated sustainability evaluation of steel slag-RAP asphalt mixtures designed for full aggregate replacement, combining laboratory performance characterisation with a performance-informed life cycle assessment (LCA). Laboratory testing covered key road-performance attributes, complemented by immersion conditioning and trace-element leaching to examine long-term feasibility and environmental safety. A high-functionality epoxy slag-RAP mixture was identified through performance screening and adopted as the representative full-replacement option for scenario parameterisation. The LCA quantified seven impact categories and a monetised ecological cost indicator, with results interpreted under a functionally consistent 30-year comparison. Under this comparison, the full-replacement option reduced global warming potential from 146.01 to 89.42 t CO₂-eq (-38.8%) and acidification from 0.58 to 0.36 t SO₂-eq (-37.9%) relative to a conventional natural-aggregate reference, with the benefits arising from both waste-based aggregate substitution and reduced intervention frequency enabled by improved durability; trade-offs were observed in eutrophication and toxicity-related indicators. Total ecological cost decreased from 182.30 × 10³ CNY for the conventional reference to 113.59 × 10³ CNY for the full-replacement option. By integrating performance-based service-life parameterisation with multi-category life cycle impact and ecological-cost monetisation, the proposed framework supports a more accurate and comprehensive evaluation of recycling-based pavement strategies and can be transferred to other infrastructure applications, while confirming that full replacement of natural aggregates by waste-derived materials can deliver substantial net life-cycle benefits.