Medium and highly sulfidic tailings are high-volume wastes that can lead to severe environmental damage if not properly managed. Due to the high content of sulfide minerals, these tailings can undergo weathering if put in contact with oxygen and water, generating acid mine drainage (AMD). The moderate-to-high sulfide content is also an important technical limitation for their implementation in the production of construction materials. This paper reviews the use of sulfidic tailings as raw material in construction products, with a focus on cement, concrete, and ceramics. When used as aggregates in concrete, this can lead to concrete degradation by internal sulfate attack. In building ceramics, their implementation without prior treatment is undesirable due to the formation of black reduction core, efflorescence, SOx emissions, and their associated costs. Moreover, their intrinsic low reactivity represents a barrier for their use as supplementary cementitious materials (SCMs) and as precursors for alkali-activated materials (AAMs). Nevertheless, the production of calcium sulfoaluminate (CSA) cement can be a suitable path for the valorization of medium and highly sulfidic tailings. Otherwise difficult to upcycle, sulfidic tailings could be used in the clinker raw meal as an alternative raw material. Not only the SO3 and SiO2-rich bulk material is incorporated into reactive clinker phases, but also some minor constituents in the tailings may contribute to the production of such low-CO2 cements at lower temperatures. Nevertheless, this valorization route remains poorly explored and demands further research.

ResumoPlanejar a aplicação das correções das manifestações patológicas em concreto armado é um ponto relevante na redução dos custos associados ao problema. Desse modo, vem à tona a possibilidade de emprego de métodos com o objetivo de relacionar as anomalias à sua prioridade de resolução. Este trabalho demonstrou o emprego da matriz de priorização GUT com esse objetivo particular. Foram apresentados registros fotográficos dos principais problemas encontrados em uma área de estudo, nos quais aplicou-se o método. Os resultados indicaram que as correções devem priorizar elementos estruturais que apresentam corrosão de armaduras. Concluiu-se que o método GUT representou uma ferramenta útil neste ramo da construção civil. Além disso, seus resultados servirão para beneficiar a empresa ou instituição através da retroalimentação do sistema, com informações acerca das principais causas e origens dos problemas, possibilitando a realização de melhoramentos para prevenção da ocorrência de manifestações.Palavras-Chave: Matriz de Priorização; Método GUT; Patologia das construções; Concreto Armado. AbstractPlanning the resolution of pathological manifestations in reinforced concrete structures is a relevant point in the reduction of costs. This brings to the fore the possibility of employing methods with the objective of relating the problems to their resolution priority. This work demonstrated the use of the GUT prioritization matrix with this particular purpose. Photographic records of the main problems found in a study area, in which the method was employed, were presented. Results show that corrosion should be corrected first. It was concluded that the GUT method was a useful tool to prioritize pathological manifestations in an area where corrections are required. In addition, its results

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The major drawbacks of earth such as low water stability and moderate strength have led mankind to stabilize the earth. It has been developed as a vernacular technique in different civilizations. Since then, the focus was mainly on gypsum, lime, or pozzolan stabilization. Recently, cement has become one of the commonly used additives in earth stabilization, which consequently reduce the environmental advantage of earth. This paper deals with a reverse engineering approach for low environmental impact earth stabilization technique, aiming the replacement of cement in earth stabilization. Various earth-mixtures were done to investigate the performance of this technique. Water contact behaviour and compressive strength of the stabilized earth specimens was determined. Moreover, the characterization of the stabilization effect has been performed through X-ray powder diffraction patterns (XRD) and clearly identify the production of ettringite using very low CO2 intensive raw materials. Furthermore, the carbon footprint of the stabilized earth-mix has been determined with the help of LCA (life cycle assessment) calculation. The laboratory analyses on this mix-design have proven a high water-resistance and the results show a remarkable increase in compressive strength. Finally, these results open a new avenue for earth stabilization and secure the implementation of this material in the conventional construction industry.

The fast precipitation of ettringite in conventional Calcium Sulfo Aluminate (CSA) cement causes rapid stiffening of the cement paste and is directly associated with short setting times and self-desiccation. To extend the time during which those types of cement remain workable, retarding admixtures can be used. However, retarders may affect the amounts and types of hydration products formed and as a consequence the ability of hydrated cement to chemically bind water. This work investigates the influence of two natural-based admixtures on the self-desiccation ability of a vernacular CSA ternary binder used as earth stabilization. Vicat measurements were used to study the efficiency of citric acid and sucrose as retarding admixtures on the setting time of stabilized earth. A quantitative study of the self-desiccation ability of the binder was performed on dried binder pastes using thermogravimetric analysis (TGA). Results show that both admixtures have a significant impact on the setting time of the binder. Furthermore, TGA showed that the self-desiccation ability of this vernacular CSA binder is significantly reduced when citric acid at high dosages is used, both at early hydration and after 14 days. On the contrary, the use of sucrose does not affect the water chemically bound at an early age but can maximize bound water after 14 days of hydration.