Durability and resilience of geopolymers incorporating iron mine tailings

The construction sector is one of the main contributors to global energy consumption and CO 2 emissions, largely due to the extensive use of Ordinary Portland Cement (OPC). In response, increasing attention has been given to alternative materials such as geopolymers, which are inorganic materials and offer a more sustainable approach while maintaining adequate mechanical and durability performance. This study investigates the possibility of incorporating Portuguese mine tailings into metakaolin-based geopolymers as a strategy for reducing environmental problems associated with abandoned mines and promoting a circular economy. Kaolin from São Vicente de Pereira was calcined to produce metakaolin, while tailings were collected from the abandoned Moncorvo, Tinoca, and Lousal mines. Raw materials and resulting geopolymers were characterized through X-ray diffraction, X-ray fluorescence, compressive strength, water absorption, and durability tests under sodium chloride, sulfate, acidic conditions, and an accelerated ageing chamber. The results showed that geopolymers with Moncorvo tailings achieved compressive strengths comparable to the reference geopolymer (100% metakaolin), reaching approximately 40 MPa after 90 days of curing. Geopolymers incorporating hematite and quartz demonstrated satisfactory mechanical performance, while formulations containing sulfate generally exhibited lower strength values. Durability tests revealed low mass variation, with some formulations showing mass losses below 0.5% and others presenting slight mass gains. Compressive strength losses after chemical exposure ranged between 3% and 25%, remaining significantly lower than values typically reported for OPC-based materials. The results demonstrate that selected tailings can be successfully valorized in geopolymer production.