Stabilization of iron ore tailing with low-carbon lime/carbide slag-activated ground granulated blast-furnace slag and coal fly ash

The massive accumulation of iron ore tailing (IOT) results in land resource wastage and increases the possibility of environmental pollution. In this study, the feasibility of using low-carbon alkali-activated ground granulated blast-furnace slag (lime/Carbide slag (CS)-GGBS) and coal fly ash (CFA) instead of portland cement (PC) for solidifying IOT was investigated. The effects of different binders on strength development and durability of cured IOT were analyzed through unconfined compressive strength (UCS), water stability, and dry-wet cycles tests. Furthermore, the microstructure characteristics of cured IOT were conducted by using scanning electron microscope (SEM) method, X-ray diffraction (XRD) analysis, and thermogravimetric analysis (TGA). The results showed that, using the low-carbon material lime/CS-GGBS to replace about 70% of PC (i.e., PC:lime/CS: GGBS=1:1:1) with 9% binder content, the strength and durability of cured IOT were significantly improved compared with using pure PC. The 28d-UCS of cured IOT was 4.86 MPa, which was twice higher than that with pure PC. The 7d-UCS of cured IOT was 8.22 MPa after 12 dry-wet cycles, which was 2.8 times higher than that with pure PC. Moreover, the water stability coefficient of 27 + 1d-cured IOT was 90%. The micro-analysis showed that, the amount of hydration products (i.e., CSH, CAH and ettringite) in IOT cured with low-carbon materials increased significantly, and the structure became denser, resulting in the increase of strength. This study develops a low-carbon binder instead of pure PC to solidify IOT, and the results can provide a theoretical basis and scientific guidance for the comprehensive utilization of IOT as a filler solid waste.