Development of supersulfated cement ternary binders with silicomanganese slag and lead-zinc smelting slag: Compressive strength, heavy metal leaching, and hydration behaviour

This study develops a novel ternary supersulfated cement (SSC) binder incorporating silicomanganese slag (SMS) and lead-zinc smelting slag (LZSS), and comprehensively evaluates its fresh, mechanical, microstructural, durability, and leaching performance. Ten concrete mixtures were designed with a constant binder content of 500 kg/m³ and a water-to-binder ratio of 0.40, with SSC replaced by up to 35 wt% SMS and LZSS. The optimised T-15–15 blend (15% SMS + 15% LZSS) achieved a 28-day compressive strength of 23.6 MPa, exceeding the 20 MPa threshold for semi-structural applications, while delivering high sulfate resistance (<0.09% expansion at 26 weeks) and a refined pore structure (0.150 mL/g total porosity). The ternary system immobilised 85.3% of Mn in the residual fraction, reducing TCLP leachate to 0.001 mg/L. Across the ternary mixtures, GWP reductions reached up to 83.1% (71.9 kg CO₂ eq/m³ for T-20–15) compared to ordinary Portland cement. The binder exhibits high carbonation susceptibility (47.4 mm at 90 days), which can be effectively managed through surface protection or by incorporating supplementary alkaline buffers in future developments. Overall, the T-15–15 binder emerges as a promising, industrially scalable, and environmentally favourable material suitable for underground infrastructure, pavement bases, and masonry blocks, offering a practical pathway for transforming hazardous waste streams into durable, low-carbon construction products.