Reinforcement Effects of Alkaline Red Mud on Tailings Activation and Performance of Their Resultant One-Part Geopolymers

Abstract

Utilizing aluminosilicate-rich mine tailings via geopolymerization provides a desirable solution for decreasing the tailings inventory when the limitation of the low activity is addressed with the cost-effective technology. Alkali-hydrothermal pretreatment can effectively enhance the activity of tailings at a temperature of ~200 °C, much lower than traditional activation methods such as high-temperature calcination and alkali fusion. However, only geopolymers prepared from activated tailings with high NaOH concentrations during the activation process can show satisfactory performance. The resulting cost remains to be further reduced. Here in this study, the alkaline red mud was utilized as a supplementary alkali source to enhance the activation effect of tailings with a view to reducing the reliance of subsequent geopolymers on the NaOH amounts. The results suggested that red mud prompted the depolymerization of tailings structures, leading to the lower relative crystallinity, higher initial pH, and higher solubility of active ions of activated tailings. As a result, the strength of their resultant geopolymers was significantly enhanced. The strength of geopolymers prepared from the activated tailings with 15 wt.% NaOH could reach 17.73 and 28.05 MPa at 3 and 28 days, respectively, much higher than that of the control sample (the 3-day and 28-day strength were only 0.73 and 1.27 MPa, respectively). This can primarily be attributed to the generation of larger amounts of geopolymer gels and the formation of denser microstructure.

Keywords: Tailings, Red mud, Solubility of active ions, Strength, Geopolymer gels