Advances in Research

Iron tailings are a high-volume solid waste generated during iron ore processing, posing considerable environmental and storage challenges. Their silica–alumina–rich composition, however, provides potential for sustainable incorporation into concrete. This review aims to evaluate the effects of using iron tailings as aggregate substitutes in concrete and to summarize recent advances in activation and modification technologies. A systematic assessment of existing experimental studies was conducted, focusing on mechanical performance, durability behavior, microstructural characteristics under various replacement levels, and activation approaches including mechanical, chemical, and microbial techniques. Evidence shows that optimal replacement ratios—20–40% for fine aggregates and 30–60% for coarse aggregates—enhance concrete density, interfacial transition zone compactness, mechanical strength, and impermeability, while also improving resistance to freeze–thaw cycles and sulfate attack. These benefits arise from micro-filling effects, interface densification, and potential secondary hydration. Excessive substitution, however, leads to poor grading, irregular particle morphology, and high water absorption, consequently reducing strength and durability. Activation technologies markedly improve the pozzolanic activity of iron tailings. Iron tailings exhibit significant potential for sustainable concrete production, contributing to solid-waste utilization and carbon reduction. Nonetheless, challenges remain regarding raw material variability, long-term durability mechanisms, and the absence of standardized guidelines for engineering practice.