Iron ore tailings stabilization with alternative alkali-activated cement for dry stacking: mechanical and microstructural insights

Upstream tailings dams are high-risk structures that have experienced several failures worldwide, particularly with iron ore tailings (IOT). In this study, new disposal methods/techniques, such as cement-stabilized dry stacking, are discussed that provide enhanced mechanical behavior while reducing failure risks. Alkali-activated materials are used as cementing agents due to their mechanical and environmental advantages compared to ordinary Portland cement. This study evaluates the mechanical and microstructural behavior of IOT stabilized with an alkali-activated cement (AAC) composed of two by-products from the IOT beneficiation process, metakaolin and sodium silicate, tested under plane strain conditions. Simple shear tests and microstructural analysis were performed. Mixtures of IOT were produced with 0%, 1%, 3%, and 5% AAC to examine the influence of such variables on strength and deformability parameters under undrained conditions. The mixtures with 3% and 5% AAC showed the greatest impact on the strength; however, the addition of 1% AAC was able to reduce positive pore-pressure generation. Cementitious bounds were evidenced by forming a sodium aluminosilicate hydrate gel. The studied AAC was effective in stabilizing IOT, even at small contents.