A Comprehensive Investigation of the Characteristics of Alkali Activated Mine Tailing-Slag Binders and Mine Tailing-Cement Binders

Alkali activated mine tailing-slag blends and mine tailing-cement blends containing mine tailings as the major binder constituent are evaluated for their setting time behavior, reactivity properties, flow characteristics, and compressive strengths. Liquid sodium silicate and sodium hydroxide are used as the activator solution. The effects of varying alkali oxide-to-powder ratio (n value) and silicon oxide-to-alkali oxide ratio (Ms value) is explored. The reactivity of all blends prepared in this study is studied using an isothermal calorimeter. Mine tailing-cement blends show a higher initial heat release peak than mine tailing-slag blends, whereas their cumulative heat release is comparable for higher n values of 0.050 to 0.100. Compressive strength tests and rheological studies were done for the refined blends selected based on setting time criterion. Setting times and compressive strengths are found to depend significantly on the activator parameters and binder compositions, allowing fine-tuning of the mix proportion parameters based on the intended end applications. The compressive strength of the selected mine tailing-slag blends and mine tailing-cement blends are in the range of 7-40 MPa and 4-11 MPa, respectively. Higher compressive strength is generally achieved at lower Ms and higher n values for mine tailing-slag blends, while a higher Ms yields better compressive strength in the case of mine tailing-cement blends. Rheological studies indicate a decrease in yield stress and viscosity with increase in the replacement ratio, while a higher activator concentration increase both. Oscillatory shear studies were used to evaluate the storage modulus and loss modulus of the mine tailing binders. The paste is seen to exhibit a more elastic behavior at n values of 0.05 and 0.075, however the viscous behavior is seen to dominate at higher n value of 0.1 at similar replacement ratios and Ms value. A higher Ms value is also seen to increase the onset point of the drop in both the storage and loss modulus of the pastes. The studied also investigated the potential use of mine tailing blends for coating applications. The pastes with higher alkalinity showed a lesser crack percentage, with a 10% slag replacement ratio having a better performance compared to 20% and 30% slag replacement ratios. Overall, the study showed that the activation parameters and mine tailings replacement level have a significant influence on the properties of both mine tailing-slag binders and mine tailing-cement binders, thereby allowing selection of suitable mix design for the desired end application, allowing a sustainable approach to dispose the mine tailings waste