Synthesis and hydration mechanism of a steel‐making by‐product based quaternary binder suitable for superfine tailings

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The high cost and carbon emissions associated with traditional ordinary Portland cement (OPC) coupled with the poor consolidation of superfine tailings (ST) have become serious problems in the cemented superfine tailings backfill (CSTB). To avert this, using industrial by‐products as a low‐carbon, low‐cost alternative binder to OPC is regarded as a promising solution. In this study, a novel steel‐making by‐product based quaternary binder (SQB) was developed using ladle slag (LS), calcium hydroxide (CH), dihydrate gypsum (DG), and ground granulated blast furnace slag (GGBFS) based on orthogonal protocols. The fresh and hardened properties of the CSTBs were evaluated at different SQB proportions, and the optimal ratio of SQB was determined using the TOPSIS method. The hydration mechanism and microstructural evolution of SQB were further systematically investigated using isothermal calorimetry analysis (ICA), x‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry and differential thermogravimetry (TG−DTG), and scanning electron microscope (SEM). The results indicated that the proportion of each component in the SQB significantly affected the rheological properties of fresh CSTB slurries. Afterward, the optimal proportion of SQB was determined to be LS:CH:DG:GGBFS = 20:5:15:60, and its uniaxial compressive strengths (UCS) at 1, 3, 7, and 28 days were 1.11, 2.82, 6.23, and 9.45 MPa, respectively, which met the requirements of mine backfill. Moreover, the quaternary SQB system demonstrates more pronounced advantages, with significantly superior performance across all curing stages compared to the corresponding ternary system (without CH). The hydration mechanism and microstructural development of SQB revealed a synergistic reaction between sulfate‐activated LS and alkali–sulfate‐activated GGBFS, resulting in the formation of a large amount of ettringite (AFt) and calcium silicate hydrate (C–S–H) gels and a denser microstructure. Overall, the synthesized SQB offers an eco‐friendly and economical alternative for CSTB, which has notable engineering application prospects.