Early-age reactivity and strength development in high volume mine tailings-based alkali activated binders and their application potential

Mine tailings (MT) present environmental and health risks, necessitating suitable waste management strategies to safely dispose them. One of the most effective methods to immobilize detrimental ingredients present in tailings, yet at the same time synthesize value-added materials in large volumes, is through the development of cementitious binders containing tailings. In this work, copper mine tailings are used to develop alkali-activated binders for several construction-related applications. The binders are designed with ≥70 % by mass of MT, along with minor additions of reactive materials such as cement (C) or slag (S), to obtain 28-day compressive strengths of up to 40 MPa when cured under ambient conditions, contrary to low strength MT-based binders that are generally reported. Setting time is used as a simple criterion to screen the mixtures. The influence of varying Na₂O-to source material (MT + cement/slag) ratio (n) and SiO₂-to-Na₂O ratio (M_s) of the activator on the calorimetric response, flow, and compressive strength development are studied in detail. MT-S blends demonstrate higher strengths (up to 40 MPa) as compared to MT-C blends (up to 12 MPa). Lower M_s and higher n values lead to higher strengths for MT-S blends, while a higher M_s yields better strength for MT-C blends. Based on the binder strength, application avenues such as structural/non-structural masonry, pre-cast non-structural/structural panels, and grouts are identified.