ABSTRACT
A preliminary experimental phase was conducted to test lime-fly ash binders in stabilizing-solidifying sulfide-rich tailings from mines in Canada. Treated and cemented tailings samples were subjected to mechanical tests alongside mineralogical characterizations. Metal and contaminant leachability from the samples was also checked using TCLP solutions. Results show that secondary minerals are responsible for solidifying samples and decreasing their permeability values. On the other hand, the geochemical stability of cemented tailings is enhanced with increasing curing periods, resulting from the precipitation of insoluble (in acid rain, in groundwater, and in acetic acid solutions) secondary minerals. It is deduced that these are hydroxy-minerals since an alkaline environment is required for their formation. They have not been identified yet but the phases are composed of Fe, Cu, Zn, Mg, and sometimes Al, with a certain part probably consisting of oxy-hydroxides. However, since the chemistry of pore water from the cemented samples is specific and evolves over time, these could be sulfate, carbonate and alumino-silicate complex phases as well. Although minerals that immobilize metals are not well defined yet, results indicate the capability of lime-fly ash binders in immobilizing heavy metals and in enhancing mechanical resistance to compressive forces and freeze-thaw cycles over a period of at least 660 days.
