Utilization of Mine Tailings As Partial Cement Replacement

Technical University of Denmark, Kgs. Lyngby, Denmark

Abstract: Depositing of mine tailings entail major economic costs and potential negative environmental impacts. Thus finding an alternative to depositing is of interest. This study focused on the use of mine tailings as a partial cement replacement, thereby preventing depositing the mine tailings. Mine tailings from two different mines Zinkgruvan (Sweden) and Nalunaq (Greenland) were both tested as 5 and 10% cement replacement. Addition of mine tailings in the fresh concrete mix affected the consistency negatively increasing the water demand, but an acceleration of hydration reactions were seen for both tailings. A lower compressive strength was obtained for mortar specimens with tailings compared to reference specimens at 7, 14 and 28 days of curing. However, both mine tailings showed indications of pozzolanic activity. This tendency was most pronounced for Zinkgruvan, indicating a higher reactivity of the oxides contributing to the pozzolanic reactions. The mine tailings has a relatively high content of toxic chemical elements, but no significant leaching of chemical elements was seen from neither the pure mine tailings nor the mortar specimens containing mine tailings. Overall, the results show that these mine tailings have potential as a partial cement replacement in cementitious mixtures.