Review on interfacial strength damage and degradation of steel slag asphalt mixtures

As a bulk solid waste, studying the resourceful utilization of steel slag in asphalt mixtures is of great significance for addressing environmental pollution and the shortage of aggregates in highway engineering. This article mainly focuses on the characteristics of steel slag, the adhesion mechanism at the steel slag-asphalt interface, the key factors affecting damage, and subsequent improvement methods. The rough and porous surface of steel slag, along with its alkaline characteristics, allows it to form interfacial bonding with acidic asphalt through both physical and chemical adsorption. However, factors such as internal f-CaO hydration expansion, iron oxide corrosion, and asphalt aging can lead to interfacial degradation. In the external environment, high temperatures accelerate asphalt aging, low temperatures cause expansion leading to cracking, water erosion weakens adhesion through hydrolysis and freeze-thaw cycles, salt erosion exacerbates interface delamination and crystal expansion, and long-term repeated loading can cause fatigue damage and creep deformation in asphalt mixtures. Compared to traditional basalt asphalt mixtures, steel slag asphalt mixtures have a fatigue life that is 4.3%–25.8% higher. In terms of moisture stability, the residual stability increased overall by 1.7%–5.1%. The resistance to freeze-thaw damage increased by 8.8%–10.3%. When the temperature rose from 50 °C to 70 °C, the dynamic stability significantly decreased, but steel slag asphalt mixtures consistently showed an advantage in dynamic stability, being 13.9%–14.3% higher than basalt asphalt mixtures. In terms of low-temperature crack resistance, the maximum strain was slightly lower than that of basalt asphalt mixtures, with only a small difference. Existing pretreatment technologies (carbonization, surface modification, aging), asphalt modification (polymers, nanomaterials), and fiber reinforcement can improve performance, but they have limitations such as f-CaO residues, high process costs, and unclear multi-factor synergistic modification mechanisms. Future research should focus on efficient pretreatment technologies, exploring the degradation mechanisms through multifactor coupling, and the synergistic optimization of steel slag and asphalt to enhance the performance of asphalt mixtures, thereby promoting the engineering application and sustainable development of steel slag asphalt mixtures.