Blast furnace slag-based binder as an eco-friendly and cost-effective material in cementitious mine backfill: Mechanisms, applications and future perspectives

In conventional cemented paste backfill (CPB), ordinary Portland cement (OPC) is the primary binder; however, it has drawbacks such as high costs and carbon emissions, and low durability. Granulated blast-furnace slag, a byproduct of ironmaking, has emerged as a promising sustainable additive. In this review, three slag-based binders—slag–cement blends (SCB), alkali-activated slag (AAS), and alkali-sulfate-activated slag (ASAS)—are discussed, focusing on their hydration mechanisms, rheological characteristics, mechanical properties, microstructure, sulfate resistance, and heavy metal solidification capabilities. SCB–CPB exhibits enhanced fluidity and late-stage strength compared to OPC–CPB, albeit with reduced early-stage strength. Although AAS exhibits superior comprehensive properties, its application is hindered by the high cost and corrosiveness of alkali activators. In contrast, ASAS emerges as a balanced solution, offering early- and late-age strength, second only to AAS, while being the most cost-effective and lowest-carbon option. Moreover, the future prospects of slag-based binders in CPB are discussed, providing valuable guidance for their formulation and application. These findings offer valuable insights for the further development and implementation of cost-effective and environmentally friendly slag-based binders in CPB applications.