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.

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.

Dispersive clays are seen as problematic geomaterials due to their structural instability associated to the presence of high amounts of sodium adsorbed to the clay minerals. Thus, such soils are prone to deflocculate in the presence of water, having the potential to cause severe damage to man-made structures. Generally, the replacement of the weakly adhered sodium cations by calcium ions through the usage of lime is effective to cease the dispersivity potential. Yet, little is known concerning the resilient modulus response of lime stabilised dispersive soils for pavement applications. Present research intends to address this gap by conducting unconfined compressive strength tests and resilient modulus tests on a dispersive soil from the Paraguayan Chaco stabilised with hydrated lime. The results of both the strength and the stiffness tests could be successfully correlated to the adjusted porosity/lime index, resulting in power-type relationships, which is the major novelty of present research.