Damage evaluation and deformation behavior of mine tailing-based Geopolymer under uniaxial cyclic compression

Geopolymerized mine tailings (MTs), as an alternative to reuse the mine wastes, can be used for construction materials (e.g., geopolymer concrete and bricks) depending on their mechanical properties. Their strength values, which can range from a couple of MPa to tens of MPa, are significant evidence for their application in the construction industry. In practice, geopolymers activated with different NaOH molarities can significantly affect the mechanical properties of MTs. The mechanical behavior of geopolymers under monotonic loading also has been widely investigated. However, the potential hazard of the exposure of geopolymer concrete/bricks to cyclic loading has received limited attention. This paper presents a study we conducted on geopolymers made by activation of MTs under cyclic loading to understand their crack and damage behaviors, including the influence of factors such as NaOH molarity and loading patterns. The influence of NaOH molarity on the elastic and plastic strains of the geopolymer specimen at different cycles was explored. A series of unconfined compression tests of cubic specimens with different NaOH molarities as well as microscopic investigations and observations via XRD, FTIR, and SEM were carried out in this study. The Young's modulus of the geopolymer was found to increase followed by a decrease with the cycles for all the selected NaOH molarities. The geopolymers activated with lowest NaOH molarity were first to start damage and activated with the highest NaOH molarity were the last to damage. The damage variable was shown to increase rapidly at the initial cycles and then gradually approached the maximum value.