Silicomanganese slag wool waste as a reinforcement in clinker-free mortar and concrete: mechanical performance, microstructural analysis, and environmental-economic benefits

Silicomanganese slag wool waste (SWW) represents a particularly intractable industrial waste characterized by its loose fibrous structure and high concentration of heavy metals, which poses severe challenges for safe disposal and resource utilization. To valorize this difficult-to-treat by-product while mitigating the carbon footprint of construction materials, this study engineered a novel clinker-free composite through the synergistic co-utilization of multiple industrial by-products (steel slag, desulfurized gypsum, and granulated blast furnace slag). The influence of SWW volume fraction (0–0.5% in mortar; 0–1.0% in concrete) was evaluated for workability, mechanical properties, and microstructure. At optimal dosages (0.3 vol% mortar, 0.5 vol% concrete), the 11.3% flexural and 8.0% tensile splitting strength gains were driven by dual mechanisms: fiber-bridging arresting cracks and pozzolanic activity densifying the C-(A)-S–H gel matrix. Conversely, excessive SWW caused fiber agglomeration and defective interfacial zones, compromising integrity. After 64 days, the solidified concrete effectively immobilizes heavy metals (Cd, Cr, Mn, Ni, Pb), significantly reducing their leaching concentrations. A cradle-to-gate life-cycle assessment demonstrates an 85.0% reduction in global warming potential and a 27.6% cost reduction versus conventional concrete, with benefits sustained under ± 20% supply chain stress (80.9% GWP reduction, 24.0% cost reduction). This research presents a technically viable, environmentally sound, and economically advantageous pathway for repurposing multiple solid wastes in sustainable building materials.