Abstract The industrial waste peoduction causes environmental damage, so it is important to reintroduce them into the production cycle to promove a more sustainable development. The present study aims to investigate the use of residual marble powder as a filler and its effects on the production of concrete for interlocking pavements. For this purpose, natural sand was replaced by 15% and 25% marble powder, these percentages being scarce in the literature on the reuse of marble waste. The physical properties of the materials used were evaluated, and the mechanical and microstructural characteristics of the developed concrete were analyzed. It was observed that marble powder improves the workability of the mixture and reduces the quantity of empty spots in the concrete, resulting in a stronger, denser, and more homogeneous material. The axial compressive resistence achieved by the concrete was close to 40 MPa, meeting the Brazilian technical standard for interlocking pavement production. It was found that the integration of waste into the production cycle is beneficial for optimizing material properties, reducing the consumption of raw materials and the associated environmental impacts of their extraction.

Resumo A produção de resíduos industriais causa impactos ambientais, por isso é importante reintroduzi-los no ciclo produtivo para promover um desenvolvimento mais sustentável. O presente estudo teve o objetivo de investigar o uso do pó de mármore residual como fíler e seus efeitos na produção de concreto para pavimentos intertravados. Para isso, a areia natural foi substituída em 15% e 25% pelo pó de mármore, percentuais pouco usados na literatura de reaproveitamento de resíduos de mármore. Foram avaliadas as propriedades físicas dos materiais utilizados e as características mecânicas e microestruturais dos concretos desenvolvidos. Notou-se que o pó de mármore melhora a trabalhabilidade da mistura e reduz a quantidade de vazios no concreto, resultando em um material mais resistente, denso e homogêneo. As resistências à compressão obtidas pelos concretos foram próximas de 40 MPa, o que atende à norma técnica brasileira para produção de pavimentos intertravados. Verificou-se que a inserção de resíduos no ciclo produtivo é benéfica por otimizar propriedades dos materiais, reduzir o consumo de matérias-primas e os impactos ambientais associados à sua extração.

abstract: In this work, the authors explore the use of iron ore tailings (IOT) from a tailings dam as a recycled precursor material in producing a composite through alkali-activation technology. Two different composite types were evaluated: paste specimens made using only IOT and an alkaline activator, and mortar specimens using the same binder and quartz sand as fine aggregate. Three different grinding times were applied to activate the IOT; a NaOH solution was used as the alkaline activator with three molar concentrations (8, 10, and 12 mol/l); and, thermal curing of 100°C for 7 days was applied. These parameters were obtained by a hard-mini-test (HMT) experimental procedure. The physico-mechanical properties of the composites were obtained, and the results showed a compressive strength up to 110.0 MPa, which is like high-performance Portland cement concretes and alkali-activated cements derived from well-established precursors reported in the literature using thermal cure.

resumo: Neste trabalho, os autores exploram o uso do rejeito de barragem de minério de ferro (RBMF), de uma barragem de rejeitos, como material precursor reciclado na produção de um compósito através da tecnologia de ativação alcalina. Dois compósitos diferentes foram avaliados: espécimes de pastas feitas usando somente RBMF e ativador alcalino, e espécimes de argamassa usando o mesmo aglomerante e areia como agregado miúdo. Três tempos de moagem diferentes foram aplicados para ativar o RBMF; uma solução de NaOH foi empregada como ativador alcalino com três concentrações molares (8, 10 e 12 mol/l); e cura térmica de 100ºC por 7 dias. Esses parâmetros iniciais foram obtidos através do procedimento experimental Endurecimento-Mini-Teste (EMC). As propriedades físico-mecânicas dos compósitos foram determinadas e os resultados mostraram uma resistência a compressão de até 110,0 MPa, que é compatível com concreto de cimento Portland de alto desempenho e cimentos álcali-ativados feitos a partir de precursores bem estabelecidos reportados na literatura usando cura térmica.

The characterization studies of tailings from mining are crucial for the development of its reuse processes and the reduction of impacts caused by its conditioning on the earth’s surface. This study characterizes the magnetic tailings from phosphate-rock processing using X-ray diffraction, X-ray fluorescence spectrometry and quantitative electron microscopy techniques. Samples were obtained from the magnetic tailings deposit of a mining company in the Alto Paranaíba region, Minas Gerais. The tailings are mainly composed of hematite/magnetite (74.92%), ilmenite (8.91%), fluorapatite (8.8%), anatase (3.07%), calcite (1.67%), goethite (1.62%), and quartz (1.02%). The particle size of the tailings is smaller than that specified for the production of sinter feed. The hematite/magnetite phase is strongly associated with ilmenite and fluorapatite. New stages of comminution and separation are needed due to the low degree of liberation of these minerals for a possible reuse of the components.

Abstract This article seeks to characterize the seed husk fiber of Moringa oleifera and understand its influence when added to a cementitious composite, in terms of mechanical performance. Moringa fibers were chemically and physically tested and were added to a cementitious composite. Specimens were molded for Ultrasonic Speed Pulse test and Uniaxial Compression Strength test, and subsequent observation in SEM. The results show a fiber with high lignin content and high absorption of water. Adding fiber to the composite, the water in the mixture is absorbed, which reduces the formation of hydrated cement compounds over time. Consequently, it results in a composite with low mechanical strength. The fiber/matrix interface analyzed in the micrographs is porous, has microcracks and a high concentration of calcium hydroxide. Despite this, the same lignin content that impairs mechanical strength in this composite is what makes the fiber resistant to weathering. More studies regarding the effectiveness of this quality should be carried out.

Resumo O presente trabalho abrange o desenvolvimento de ladrilho hidráulico sustentável (LHS) produzido com rejeitos de barragem de minério de ferro (RBMF). Inicialmente, a avaliação técnica e a análise ambiental do RBMF foram realizadas através de testes de caracterização física, química e morfológica, lixiviação e dissolução. Sua viabilidade como pigmento também foi investigada. Posteriormente, a análise de valor foi realizada, partindo de um mapa de empatia até o estudo sobre valores ambientais, sociais e emocionais na relação entre pessoas e produtos. Como resultado, o RBMF se apresentou como partículas finas, cristalinas, sem toxicidade, sendo tecnicamente viável para ser empregado como fíler, agregado e pigmento na produção de LHS. A camada de cor do LHS apresentou cores mais homogêneas e menos poros do que as convencionais. Assim, o projeto do LHS foi desenvolvido, incorporando valores intangíveis como: ideologia ambiental, identidade local e expressão social. Nesse sentido, o presente trabalho busca ajudar nas tomadas de decisão envolvendo RBMF como material de construção.

Abstract The present work discloses the development of a sustainable cement tile (SCT) produced with Iron Ore Tailings from tailings dams (IOT). Initially, technical evaluation and environmental analysis of IOT were performed through physical, chemical and morphological characterisation, leaching and dissolution tests. Its feasibility as a pigment was also investigated. Subsequently, the value analysis was performed, starting from an empathy map to a study on environmental, social and emotional values in the relationship between people and product. As result, the IOT presented fine, crystalline particles, no toxicity, and is technically feasible to be employed as filler, aggregate and pigment in the production of SCT. The colour layer of the SCT presented more homogeneous colour and less pores than conventional ones. Therefore, the design of the SCT was developed, incorporating intangible values such as: environmental ideology, local identity and social expression. In this sense, the present work seeks to assist in the decision-making process involving IOT as construction material.