Utilization of steel slag for cemented tailings backfill: Hydration, strength, pore structure, and cost analysis

Abstract High-value utilization of steel slag in cement is limited due to its low reactivity, volume instability, and restrictions in the construction industry. In this study, a novel steel slag binder (SSB) was proposed for cemented tailings backfill (CTB). The hydration process and mechanism were summarized and examined through thermogravimetric and X-ray diffraction analysis. The SSB-CTB properties of long-term compression strength, shrinkage, pore distribution, and microstructure were investigated. Furthermore, the cost breakdown and prospects of high volume steel slag dosage were also explored. The results show that the SSB hydration mechanism combines alkali activation, sulfate activation, and pozzolanic effect, maximizing the reactivity and minimizing the expansion issues associated with steel slag. The long-term SSB-CTB strength gain follows a power model, owning to the positive refining effect. Although sulfate attack could coarsen pore structures, the strength property is interaction effects of positive and negative causes. The direct manufacturing cost of SSB is more than 100 CNY/t lower than OPC and GBFS blend binders. SSB with 50 wt.% steel slag dosage shows potential binding performance, while the long-term properties need to be addressed. The findings can extend the steel slag’s high-value utilization method and provide an alternative cost-saving binder for mine backfill.