Microstructure and Dissolution of Aluminosilicate Geopolymers Made from Mine Tailings Source Material

Geopolymers created from alkali activator and aluminosilicate source material offer a promising alternative to ordinary Portland cement concrete. This study explores geopolymers created from gold mine tailings and probes the connection between microstructure and dissolution. The geopolymers were cured for 7 days in the oven, in either covered or uncovered conditions. The specimens were then immersed in ultrapure water for 7 days and the resulting strength loss and increase in void space were recorded. The uncovered specimens fared better in the dissolution test, but still experienced strength losses of 75% as compared to the intact specimens. The internal surface area of the uncovered specimens increased tenfold, and the void space increased dramatically (especially for pores around 400 nm in diameter). The covered curing only increased these phenomena, with strength losses of up to 90% and an even greater increase in internal surface area and void space. These significant losses are due to the dissolution of the aluminosilicate gel, which leaches out of the specimen and is replaced by additional voids. The phenomenon of geopolymer dissolution in water must be considered in future durability studies and remedied for this class of materials before geopolymers may be used more widely in industry applications.