Comprehensive Characterisation of Alkali‐Activated Geopolymer Materials Incorporating Pb–Zn Mining Waste: Durability and Environmental Performance

This study aims to valorise mining waste from the Tunisian Guarn El Halfeya abandoned Pb-Zn mine and to assess its potential as a low-cost secondary raw material for the production of alkali-activated geopolymer materials (AAGMs), offering a dual environmental benefit: waste reuse and immobilisation of potentially toxic elements (PTEs). Unlike conventional studies relying exclusively on synthetic or industrial precursors, this work partially or fully substitutes metakaolin, the benchmark precursor, with unprocessed mine tailings, highlighting the direct applicability of raw geological by-products. Formulations were activated with NaOH at 8, 10 and 12 M and then cured at 60°C for 7–28 days. To characterise the raw materials and to optimise the AAGMs, several techniques were employed, including XRD, XRF, granulometry, TG/DTA, FTIR an dielectric spectroscopy, mechanical strength, SEM and leaching tests. Results of mine waste characterisation revealed a high content of calcite-rich matrix associated with quartz and a median particle size of 14.5 μm. AAGMs produced with ≤ 50 wt% waste and activated with 10 M NaOH exhibited strong physicochemical performance, effectively stabilising PTEs while achieving high compressive strength, making them promising candidates for contaminated site remediation and sustainable construction materials. Leaching tests clearly indicate that the composition of the AAGMs strongly affects the chemical stability and mobility of PTEs. Notably, dielectric spectroscopy, rarely applied in this field, reveals a microstructural transition: as waste content increases, isolated conductive particles progressively form interconnected ionic transport networks, providing new insights into the structure-property relationships of mine-waste-based geopolymers.