Valorisation of mine tailings in blended cement: Material performance and life cycle assessment

Portland cement production is a major contributor to global CO₂ emissions, while large volumes of mine tailings remain stockpiled as long-term environmental liabilities. This study investigates valorisation of copper mine tailings (CMT) as a supplementary cementitious material within a resource recovery framework. Intrinsic reactivity was quantified using the R³ test and linked to hydration behaviour through isothermal calorimetry, X-ray diffraction, FTIR and scanning electron microscopy, alongside compressive strength evaluation. The CMT exhibited an R³ heat release of 156 J/g, confirming its intrinsic pozzolanic reactivity. Isothermal calorimetry showed that a 10% clinker replacement reduced cumulative heat release by only 2.67%, indicating partial compensation of clinker dilution through filler and pozzolanic effects. A cradle-to-gate life cycle assessment employing system expansion quantified environmental benefits from clinker displacement and avoided tailings storage burdens. Climate change impacts decreased from 0.935 to 0.583 kg CO₂-eq with increasing CMT replacement, despite an 1800 km transport distance. Impact reductions were predominantly driven by clinker substitution, with additional gains from mitigating waste accumulation. These findings demonstrate a technically viable pathway for integrating CMT into lower-carbon blended cement.