This study evaluates the alkali activation of a binary system composed of sugar cane bagasse ash and carbide lime as a green stabilization technique for bauxite tailings (BTs). To analyze the feasibility of this alternative binder as a stabilizer, mechanical tests were performed to measure the strength, stiffness, and durability of BT binder mixtures. As a control group, tailings were stabilized with high-initial-strength portland cement (Type III). The results show that the alternative binder is a suitable option to improve the mechanical behavior of bauxite tailings. The porosity/binder index ($\eta /B_{iv}$ ) was an appropriate parameter for evaluating BT stabilization. Reduced porosity and increased binder content (decreased $\eta /B_{iv}$ ) led to an improvement in the mechanical behavior of the studied mixtures.

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.

Effective binders with low environmental impacts are of great importance for sustainable engineering practices. Parameters controlling loss of mass and stiffness degradation of ‘green’ stabilised bauxite tailings (BT) were evaluated. The porosity/binder index (η/Biv) was investigated. This index allows unification of all experiments in a single relation for a specimen's porosity and binder content, resulting in a rational dosage methodology for any soil–binder blend, replacing conventional (trial and error) strategies that are laborious and time consuming. Wetting–drying cycles (durability tests) and pulse velocity tests were performed. The alkali-activated binder was composed of sugarcane bagasse ash and carbide lime (precursors) and sodium hydroxide (alkaline activator). For comparison, BT were also stabilised with Portland cement. For both cementing agents, stiffer specimens were less susceptible to the abrasive action of durability cycles. Diverse stiffness behaviours were observed due to the different curing periods needed for the development of chemical reactions for each binder. η/Biv was found to be an appropriate parameter for evaluation of loss of mass and stiffness degradation: lower porosity and higher cement content resulted in better mechanical performance. Through η/Biv, engineers can choose the best option for a project by decreasing porosity (increasing soil compaction) and reducing the binder content or, inversely, increasing porosity while raising binder content.