Improving soil properties by adding stabilizing materials, such as cement, has garnered significant attention from researchers, particularly for enhancing soils often deemed poor geotechnical quality. This approach becomes even more advantageous when applied to increase the stability of mining tailings deposits and ensure environmental safety. This study investigates the effects of cement addition and dry density on the strength and durability of compacted bauxite tailings-cement blends. The porosity/cement index, widely used in soil-cement mixture research, was adopted to analyze the parameters that control the strength and durability of these blends. Results demonstrate that increasing cement content and dry density significantly improves unconfined compressive strength (qu) and reduces accumulated mass loss (ALM) during wet/dry cycles. The porosity/cement index effectively describes the variations in qu and ALM, as expressed by an empirical equation, which can be highly beneficial for the practical application of treated mining tailings as construction materials.

The increasing global demand for metals, driven by technological progress and the energy transition, has led to an acceleration in the expansion of the mining and metallurgical industry, resulting in an increase in the generation of mine tailings. This waste, which is of heterogeneous composition and has high contaminant potential, represents significant environmental and social challenges, affecting soils, water, and the geotechnical stability of tailings. The accumulation of these mine tailings poses a problem not only in terms of quantity, but also in terms of physicochemical composition, which exacerbates their environmental impact due to the release of heavy metals, affecting ecosystems and nearby communities. This article reviews the potential of geopolymerization and 3D printing as a technological solution for the management of tailings, offering an effective alternative for their reuse as sustainable building materials. Alkaline activation of aluminosilicates facilitates the formation of N-A-S-H and C-A-S-H cementitious structures, thereby providing enhanced mechanical strength and chemical stability. Conversely, 3D printing optimizes structural design and minimizes material consumption, thereby aligning with the principles of a circular eco-economy and facilitating carbon footprint mitigation. The present study sets out to compare different types of tailings and their influence on geopolymer reactivity, workability, and mechanical performance. In order to achieve this, the study analyses factors such as the Si/Al ratio, rheology, and setting. In addition, the impact of alkaline activators, additives, and nanoparticles on the extrusion and interlaminar cohesion of 3D printed geopolymers is evaluated. These are key aspects of their industrial application. A bibliometric analysis was conducted, which revealed the growth of research in this field, highlighting advances in optimized formulations, encapsulation of hazardous waste, CO2 capture, and self-healing geopolymers. The analysis also identified technical and regulatory challenges to scalability, emphasizing the necessity to standardize methodologies and assess the life cycle of materials. The findings indicated that 3D printing with tailings-derived geopolymers is a viable alternative for sustainable construction, with applications in pavements, prefabricated elements, and materials resistant to extreme environments. This technology not only reduces mining waste but also promotes the circular economy and decarbonization in the construction industry.

The mining sector plays a significant role in the economic development of countries by contributing to their gross domestic product. Once the demand for commercialized ore grows, the mining industry looks for new technologies to boost exploration and manage residue disposal. One promising technique to dispose of these residues is dry stacking. This research investigates the behavior of cemented iron ore tailings (IOTs) that use unconfined compression strength (UCS) and triaxial testing. The UCS tests investigated different dosages of cement-tailings compacted blends. In addition, nine triaxial tests were carried out, where six were cured under atmospheric pressure, and three were cured under 300 kPa. Samples were sheared under mean effective stresses of 300 and 3,000 kPa. Both curing conditions were subjected to drained axial loading, constant mean effective stress (p '), and lateral unloading stress paths. The results indicate that the porosity/cement index (eta/Civ) could control the mixtures' UCS. The triaxial tests revealed the effective strength parameters stress dependence. Samples that were consolidated under high stress might experience bond breakage, which leads to a decrease in the friction angle and a tendency toward critical state conditions. No meaningful variation was observed between samples that were cured under stress and atmospheric pressure.

In the field of engineering, sustainable solutions that can generate lower environmental impacts, either through material replacement or reuse, are increasingly sought after. In Brazil, in the geotechnical area, there is a demand to find solutions to avoid the disposal of tailings sludge destined for structures, following the recent dam ruptures of Fundao in 2015 and Corrego do Feijao in 2019. One of the recent investments is in the treatment of tailings, generating by-products. To improve the mechanical properties of these by-products, geopolymer utilization has been employed. Geopolymers are products resulting from reactions between aluminosilicate precursors and alkaline activators. The objective of this study is to evaluate the unconfined compressive strength of an iron ore tailings by-product stabilized with a geopolymer that utilizes perlite waste as a precursor and sodium hydroxide as an activator through a two-part alkali-activation process. Two molar concentrations of activators, 2M and 5M, and two sample compositions were evaluated: one with 20% geopolymer and 80% iron ore tailings by-product, and another with 30% and 70%. An increase in unconfined compressive strength was observed with higher concentrations of the activator solution and a greater percentage of geopolymer in material stabilization. Thus, it can be stated that the use of geopolymers in by-product stabilization is promising, but finding the optimal dosage and evaluating other variables such as curing time and temperature is necessary.