Solidification/stabilization of gold mine tailings using calcium sulfoaluminate-belite cement

Abstract

In this study, calcium sulfoaluminate-belite cement (CSAB) was used to stabilize gold mine tailings, which are challenging materials to effectively immobilize due to high heavy metal and sulfate content. The hydration of CSAB cement yields ettringite and monosulfate with good capability for immobilizing sulfates and oxyanions in their crystal structure, in addition to physical encapsulation/solidification in a cementitious matrix. Different mix designs of CSAB cement and mine tailings were prepared, and the samples were cured at room temperature. Mechanical strength and heavy metal leaching were analyzed after 7 days, 28 days, and 90 days of curing, and the phase composition (XRD), thermogravimetric analysis (TGA), and microstructure (FESEM) were also studied. All harmful elements (cationic and oxyanion elements) were effectively immobilized during 7 days of curing, and the heavy metal immobilization remained constant after longer curing, according to an environmental leaching test. High mechanical strength results and good sulfate immobilization were obtained with mine tailing content up to 50 w-% of total binder material. With higher mine tailing content (75 w-% and 90 w-%), the mechanical strength and immobilization ability substantially decreased.