Preparation of Environmentally Friendly Low Autogenous Shrinkage Whole-tailings Cemented Paste Backfill Material from Steel Slag
Using steel slag (SS), iron ore tailings (IOT), granulated blast furnace slag (GBFS), carbide slag (CS), flue gas desulphurization gypsum (FGDG) and cement clinker (CC) with a mass fraction of 9.6% as cementing agents (CA) of SIGCFC in a cascade grinding process and IOT as aggregate, a filling material for mine cemented paste backfill (CPB) material was prepared. The effect on the physical and mechanical properties, autogenous shrinkage and hydration products of CPB material mixed with SS powder were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Field emission scanning electron microscope (FE-SEM), and the mechanism of SS restrained autogenous shrinkage on the backfill body was also discussed. When the SS powder was 20% in the CA, the autogenous shrinkage of backfill block reduced 30.9% than backfill block without SS after 14 d. The results showed that the main reasons of restrained autogenous shrinkage were hydration expansion of the dead burned free lime (f-CaO) and magnesia (f-MgO) in the SS. The SS was activated by ultrafine grinding, and then added into backfill body. The f-CaO and f-MgO was highly dispersed in backfill body, which hydration expansion was not reducing the strength backfill body. In the middle and later age of the hardening process of backfill body, the coordinated growth of the ettringite (AFt) and C-S-H gel restrained the autogenous shrinkage and improved the mechanical properties.