Self-healing and performance evaluation of hot mix asphalt containing steel slag aggregates

Repetitive traffic and environmental exposure cause progressive asphalt decay, highlighting the urgent need for durable, eco-friendly pavement solutions. This study examines the role of steel slag in enhancing the self-healing capability of hot mix asphalt (HMA) under induction heating. Asphalt mixtures containing 20%, 30%, 40% and 50% steel slag were tested for fracture energy recovery, moisture susceptibility, resilient modulus, rutting resistance, and microstructural analysis. The mixture with 30% steel slag (MS30) showed the most effective healing response, achieving 81.4% fracture energy recovery and a 42.4% increase in rutting resistance. DMA results further confirmed the superior viscoelastic behaviour of MS30, with a broader relaxation window (tan δ > 1 between 35 and 65 °C) and a smoother stiffness decay, indicating improved molecular mobility and binder diffusion. The pre-healing performance indicated a higher cracking resistance index (CRI) and critical strain energy release rate (CSERR), while post-healing retention remained high at 82.1% (CRI) and 80.5% (CSERR), demonstrating strong fatigue and crack-healing potential. The MS40 mixture also showed enhanced moisture resistance (87.1%) and healing retention (85%). SEM and FTIR analyses confirmed better adhesion and reduced oxidative ageing. Overall, steel slag serves as a thermally conductive, eco-efficient functional aggregate that significantly bolsters the induction healing and mechanical properties of asphalt mixtures, thereby extending the pavement service life and long-term sustainability.