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  1. The largest hurdle for the reuse of mine tailings as a source material for geopolymerization and the production of construction materials is the tailings’ low reactivity. The highly crystalline tailings require a strongly basic alkali activator, which is user hazardous and unfavorable for industrial use. In order to increase the reactivity of the mine tailings, pre-treatment methods can be used to reduce the crystallinity and increase the solubility of aluminosili-cates. Thermal pretreatment was able to increase the solubility of silicon and aluminum, but this did not seem to be directly related to the increase in amorphous content. Thermochemical pre-treatment was even more effective than purely thermal pretreatment for increasing the quantity of amorphous phase and producing soluble aluminosilicates that can be available for geopolymerization reactions. The aluminum solubility of pretreated tailings is closely related to the quantity of muscovite present after the treatment. Further research is needed to assess the effectiveness of pretreatment for geopolymerization of mine tailings and to link the amorphous content to the solubility of aluminosilicates. Mechanical and durability evaluation of geopolymers made from pretreated mine tailings is ongoing. 
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  2. null (Ed.)
    Fracturing in brittle rocks exhibits a significant nonlinear region surrounding the crack tip called the fracture process zone (FPZ). In this study, the evolution of the FPZ under pure mode II loading using notched deep beam under three-point loading was investigated. The experimental setup included the simultaneous monitoring of surface deformation using the two-dimensional digital image correlation technique to characterize various crack characteristics such as its type and FPZ evolution in Barre granite specimens. Both displacement and strain approaches of the two-dimensional digital image correlation were used to identify the mode of fracture under pure mode II loading. Both approaches showed that the crack initiation occur under mode I despite the pure mode II loading at the notch tip. The displacement approach was used for characterizing the evolution of the FPZ which analyzed the crack tip opening displacement and crack tip sliding displacement to identify the transition between the three stages of FPZ evolution, namely, (a) elastic stage, (b) formation of the FPZ, and (c) the macro-crack initiation. The results showed that the evolution of the FPZ of mode I fracture under pure mode II loading is similar to cases of pure mode I loading of the same rock. 
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  3. null (Ed.)
    Fracturing in brittle rocks with an existing crack results in the development of a significant nonlinear region surrounding the crack tip called the fracture process zone. Various experimental and numerical studies have shown that the crack tip parameters such as the crack tip opening displacement (CTOD) and the fracture energy are critically important in characterizing the fracture process zone. In this study, numerical simulations of rock specimens with a center notch subjected to three-point bending were conducted using the extended finite element method (XFEM) along with the cohesive zone model (CZM) to account for fracture process zone. The input parameters of CZM such as the elastic and critical crack opening displacements were first estimated based on the results of three-point bending tests on the center notched Barre granite specimens. Displacements were measured using the two dimensional digital image correlation technique and used to characterize the evolution of the fracture process zone and estimate the parameters of the cohesive zone model. The results from the numerical simulations showed that CZM provided a good agreement with experimental data as it predicted all three stages of cracking from fracture process initiation to macro-crack growth. 
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