Abstract

MgO activated ground granulated blast furnace slag (GGBFS) is a form of alkali-activated composite, which is successfully used as a binder in the stabilization of highly sulfidic mine tailings. The aim of this study was to compare alkali activated composite (AAC) and ordinary Portland cement (PC) as stabilization agents, as well as their efficiency to stabilize sulfidic tailings and the results of three different diffusion and leaching methods. The Life Cycle Assessment (LCA) method was used to compare the environmental impacts of the binders. The lab-scale program covered hydraulic conductivity, compression strength, and freeze-thaw resistance tests of the stabilized tailings. The results indicate that the hydraulic conductivity (6.08 · 10⁻⁹ m/s) and compressive strength (11.5 MPa at 28 days) of AAC were better in comparison, if the corresponding amount of PC (2.04 · 10⁻⁸ m/s and 10.3 MPa at 28 days) was used. LCA shows clear ecological benefits when using AAC instead of PC in terms of lower global warming potential. Diffusion and leaching tests indicated better immobilization efficiency of AAC than PC concerning As, Cr, Cu, Ni, Se, Zn, and especially Mo. In comparison with plain tailings, AAC stabilization reduced leaching of As, Cr, Cu, Mo, Ni, Pb, Se, Zn, Cl, and SO₄ better than PC.