Use of rest products as additive in tailings paste for the mitigation of ARD : Effect of green liquor dregs and fly ash addition on geotechnical stabilization of tailings

This study focuses on the effect of green liquor dregs (GLD) and fly ash (FA) on geotechnical stabilization of tailings, using shear strength test.The objectives were to evaluate thickening of tailings using GLD to paste to improve its water retention and to reduce waste percolation, to identify optimal proportion of additives regarding geotechnical stabilization of tailings, and to study the role of FA in the decrease of porosity and thus to reduce oxygen diffusion via hardening process.The results showed that GLD is a potential material for tailings stabilization by decreasing water percolation and improving water retention property. However, the paste of GLD amended tailings withstands low shear strength. The addition of FA to the paste greatly improves shear strength which is up to 2-3 times higher. Moreover, the fly ash hardening process effectively reinforces the strength of GLD amended tailings paste. Longer curing period (3 months) for specimens leads to up to 2-3 folds higher strength compared to that of 1 month. Hydraulic conductivity is reduced as a result of GLD and FA addition, since the porosity of the tailings decreased. If reduced porosity, improved water retention capacity and no cracks are ensured in the tailings, oxygen diffusion can be limited.Godkänd; 2012; 20120608 (yuojia)