Fracture properties of the gold mine tailings-based geopolymer under mode I loading condition through semi-circular bend tests with digital image correlation

Abstract

Sustainably reusing mine tailings and reducing the economic costs of storing them is an ongoing concern in the geomechanics field. This paper discusses the process of utilizing MTs in the manufacture of geopolymer through alkaline activation. Since geopolymer is subjected to various external and internal loading conditions that could result in failures and fractures, understanding the fracture behaviors of MTs-based geopolymer is critically important for its use and application. The fracture behaviors of geopolymer remain largely unexplored. The study presented in this paper addressed this knowledge gap by evaluating the mode I fracture tests that are commonly used in the rock mechanics field for adoption to test geopolymer by using three-point bending instrument and considering various influential parameters, such as notch depths. The geopolymer specimens in this study were cast into cylindrical molds by mixing different mine tailings with a 10 M NaOH solution at a water/tailings ratio of 22% and then cured with a slightly elevated temperature of 72 ± 2℃, for seven days. Thereafter, the cylindrical specimens were cut into semi-circular specimens and a series of semi-circular bending tests were performed. The mode I fracture toughness, KIC, of the geopolymer were estimated and the sensitivity of the notch depth was evaluated based on linear elastic fracture mechanics for the specimens with current sizes. Also, the strain behaviors of the semi-circular specimens were investigated through digital image correlation mapping. The mode I fracture behaviors were studied and the force-displacement behaviors of the semi-circular bending specimens with regard to the notch depths were compared and interpreted. Further, the strain properties of the semi-circular bending specimen were evaluated with respect to different load levels and the fracture process zone and crack tip opening displacement of the geopolymer then were measured by digital image correlation analyses.