Potential Reuse of Andean Highlands Tin Tailings in Geotechnical Works Through Geopolymer Binder Stabilization

This paper presents a study on the stabilization of hazardous tin mine tailings (TMT) using a metakaolin-based geopolymer binder for their potential reuse as geomaterials in geotechnical works. The extensive laboratory testing evaluated the mechanical properties, such as unconfined compressive strength, and the durability properties, including mass loss during freezing–thawing and wetting–drying cycles. Environmental assessment included the analysis of leached heavy metal concentration using Toxicity Characteristic Leaching Procedure (TCLP). Additionally, Scanning Electron Microscopy (SEM) was conducted to investigate the microstructure of the stabilized TMT. Satisfactory results show that improvements in mechanical and durability properties depend on variations in metakaolin content, NaOH molarity, and compaction density. The novel porosity/binder index (η/B_iv) has proven to be effective in predicting the behavior of mixtures. Additionally, it demonstrated that freezing–thawing cycles have a more adverse impact on the durability of the examined mixtures. Laboratory results for mechanical strength, durability, and immobilization of hazardous heavy metals demonstrate the potential performance of TMTs for safe reuse in geotechnical works, specifically as a geomaterial for subbase and base layers of pavement exposure to severe environment and climate of the Andean highlands.