Properties and Microstructure of Low-Carbon Whole-Tailings Cemented Paste Backfill Material Containing Steel Slag, Granulated Blast Furnace Slag and Flue Gas Desulphurization Gypsum
Using steel slag (SS), granulated blast furnace slag (GBFS) and flue gas desulphurization gypsum (FGDG) as cementing agents (CA) and iron ore tailings (IOT) as aggregate, a filling material for mine cemented paste backfill (CPB) material was prepared. The mixing ratio and properties of CPB were investigated. The hydration products and microstructure of CA were analyzed by X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), and Scanning electron microscopy (SEM). The optimal proportion of CA is as follows: GBFS 58%, SS 29% and FGDG 13%. When binder sand ratio (CA/IOT) of CPB material is 1:4, and the slurry concentration is 80%, the slurry of meets the fluidity requirement of paste pumping. The compressive strength of the backfill at 28 d is 8.41 MPa, which meets the requirements of mine filling strength. After the hydration of the mineral phases in the raw materials, a large number of ettringite (AFt) and complex C-S-H gel with low crystallization degree are generated. They interweave together to make the system compact and have good mechanical properties.