The increasing production of iron ore has led to the accumulation of iron ore tailings (IOTs), which pose significant environmental and safety risks when stored in tailings dams. This study investigates the potential of IOTs as a precursor in alkali-activated binder systems, aiming to provide a sustainable solution for mining waste management. Industrial calcium carbide lime and sodium silicate (Na2SiO3) were used as activators in varying concentrations (Na2SiO3: 10%, 15%, 20%, 25%, and 30%; carbide lime: 5%, 7.5%, and 10%), with curing conditions of 23 °C for 7 days. Techniques including unconfined compressive strength tests, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and metal leaching tests were employed to evaluate the mechanical performance and environmental safety of the alkali-activated binders. The results reveal that a mixture containing 20% Na2SiO3 and 10% carbide lime achieved the highest compressive strength of 0.33 MPa at 7 days. The binder also showed negligible metal leaching, meeting environmental safety standards. These findings confirm the viability of using IOTs in the development of durable, eco-friendly construction materials, offering a scalable and sustainable solution for the management of mining waste and promoting circular economy principles in the construction sector.

Alkali-activated materials derived from industrial waste are promising alternatives to Portland cement for geotechnical applications. However, their environmental safety under realistic exposure conditions remains poorly understood, particularly due to the limitations of conventional chemical assessments, which may not capture early-stage curing effects, leaching behavior, and associated ecotoxicological risks. This study investigates whether conventional chemical assessment methods are sufficient to evaluate the environmental performance of such materials. An alkali-activated cement produced from photovoltaic module glass and hydrated oyster shell lime was evaluated through an integrated approach combining leaching tests and ecotoxicological assays. Leaching behavior was assessed at curing ages ranging from 7 to 91 days. Ecotoxicological effects were evaluated using extracts obtained from the alkaline cement after 7 days of curing, with zebrafish embryos under both acetic acid‑extracted and water-extracted conditions. Leaching tests showed a progressive reduction in several regulated metals; however, Ba, Cd, Cu, Ni, Pb, and Zn exceeded regulatory thresholds at specific curing ages. All mixtures produced highly alkaline leachates (pH > 13), and non-regulated elements (Ga, In, K, and Li) were also detected. Ecotoxicological assays revealed acute toxicity in acetic acid‑extracted leachates and sublethal effects in water- extracted leachates, including impaired hatching and reduced spontaneous movement. The results demonstrate that reductions in leached concentrations and compliance with conventional chemical criteria do not necessarily correspond to biological safety, highlighting the need to integrate ecotoxicological assays into environmental assessments of sustainable cementitious materials. Graphical Abstract

A novel alkali-activated binder was developed using processed glass from photovoltaic modules (PMG) and hydrated oyster shell lime (HOSL), and sodium hydroxide. The formation of cementitious gels was investigated over time, assessing the influence of alkali content on mechanical strength, chemical and molecular properties. Unconfined compressive strength test and Fourier-transform infrared spectroscopy were performed, supported by statistical analyses. PMG particles up to 850 μm showed evidence of surface dissolution, a behavior not previously reported. Hydration was dominated by C─S─H gel, with compositional changes observed after 28 days, including amorphous silica precipitation. After 63 days, redistribution of structural water and carbonate formation were identified. Compressive strength reached 2.88 MPa at a PMG/HOSL ratio of 4 and alkali concentration of 3 M. These findings underscore the potential of the novel binder for geotechnical applications, such as soil and tailings stabilization, and provide new insights into the hydration mechanisms in alternative binder.