Steel Slag for Roadway Construction: A Review of Material Characteristics and Application Mechanisms

Steel slag (SS) is regarded as a potentially promising alternative material for road construction, which could ameliorate the shortage of high-quality aggregate and environmental pollution of SS accumulation simultaneously. However, except for some developed countries, the comprehensive utilization rate of SS in developing countries is particularly limited, especially in road construction. This is attributed to the concerns and uncertainties of environmental and mechanical properties caused by the incorporation of SS into pavement. Therefore, a systematic literature review is conducted to explore the status quo and challenges of SS application in road domain to help develop appropriate utilization strategies. Thanks to the excellent antiabrasion, rich angularity, rough texture, and high hardness, SS aggregate possesses favorable interlocking capability that can be utilized in subgrade, base, and surface course. Additionally, when used in surface, it can be considered as a functional material, for instance for antiskidding, noise reduction, and conductive concrete for crack healing and ice melting. The current investigations are still widely interested in performance verification and expansion treatment, but lack relevant mechanism-based analysis. Further rational studies are required in terms of gelation activation technology, adhesion injury, mesoscale skeleton optimization, evaluation of healing efficiency, and long-term performance. Moreover, the environmental assessments including heavy metal and leachate contaminations are necessary for the adoption of SS in pavement.