Stabilization of iron ore tailings with fly ash as binder material for sustainable backfill applications: mechanical, environmental, and microstructural assessment

Iron ore tailings (IOT), a by-product of mining, present significant environmental challenges due to their disposal. Previous studies have explored the use of IOT in construction and geotechnical applications, but limitations such as inadequate strength development and environmental concerns have restricted its widespread adoption. The motivation for this study stems from the need for a sustainable and effective solution to repurpose IOT while addressing these challenges. This study investigated a sustainable approach to utilizing IOT as a backfill material by incorporating fly ash (FA) to enhance its mechanical properties. The mix proportions of FA to IOT were 3%, 6%, 9%, and 12%, and the maximum dry density, optimum moisture content, and strength parameters were analyzed. The morphological and mineralogical characterizations were also conducted for both materials. The optimum mix, containing 9% fly ash, achieved a maximum unconfined compressive strength (UCS) of 901.25 kPa at 28 days, exceeding the required strength for void filling (150–300 kPa) and approaching the threshold for free-standing wall support (1 MPa). The toxicity characteristics leaching procedure (TCLP) confirmed that the heavy metal concentrations in IOT are within permissible limits, ensuring environmental safety. These findings demonstrate the potential of IOT-FA composites as a cost-effective and eco-friendly solution for backfill applications in the mining and construction industries. By converting industrial by-products into functional materials, this study contributes to sustainable waste management and promotes resource efficiency in geotechnical engineering applications.