Comprehensive Review of Thermally Induced Self-Healing Behavior in Asphalt Mixtures and the Role of Steel Slag

Asphalt pavements face escalating challenges from traffic loading, climate change, and material degradation, necessitating innovative maintenance solutions. Thermally induced self-healing technologies, leveraging the viscoelastic properties of asphalt binders, can autonomously repair microcracks through targeted thermal activation. This review explored thermally induced self-healing in asphalt mixtures, with a focus on leveraging steel slag as a functional aggregate to enhance sustainability and durability. Two thermal-activation methods, electromagnetic induction and microwave heating, were critically analyzed, highlighting their distinct advantages in heating efficiency, depth, and uniformity. Steel slag offers dual benefits: improving mechanical interlock and skid resistance in mixtures while facilitating efficient heat generation via electromagnetic induction or microwave heating. However, challenges such as hydration-induced expansion, heterogeneous slag composition, and energy-intensive heating processes impede widespread adoption. Pretreatment methods, including natural aging, carbonation, and surface modifications, are essential to mitigate volumetric instability and optimize slag performance. Key factors influencing healing efficacy, including binder properties, operational parameters (e.g., microwave power, frequency), and environmental trade-offs, were systematically evaluated. Future research directions emphasized standardized pretreatment protocols, hybrid heating technologies for uniform temperature distribution, and smart-infrastructure integration for predictive maintenance.