Gisleiva Cristina dos Santos Ferreira

The scarcity of natural resources worldwide has encouraged the reuse of industrial waste in cementitious materials. In this context, waste foundry sand (WFS) is a promising material for replacing common sand (CS) in non-structural mortars. This study reviews the literature on mortars containing WFS through a structured search and selection process. The review evaluates the mechanical properties of mortars considering WFS characteristics, mix proportions, specimen geometry, and workability conditions, while also discussing sustainability, circular economy benefits, and potential environmental risks. The reviewed literature revealed inconsistencies in the mechanical performance of mortars containing the same WFS replacement level. The reduction in compressive strength (CS) showed a low linear correlation with replacement level (R² = 0.63). WFS replacement levels between 10 and 25% resulted in CS reductions ranging from approximately 2 to 26%, while higher replacement levels (30%, 50%, and 100%) led to reductions of up to 75%. Furthermore, many studies employed unusual mortar mix designs and failed to evaluate important properties for rendering mortars, such as modulus of elasticity and adhesion strength. Incomplete reporting of experimental parameters also hinders comparisons among studies and contributes to the inconsistencies observed in the literature. Although WFS pretreatment and calcination may enable higher replacement levels, further research is required to assess their compatibility with circular economy principles and their overall environmental benefits. Graphical Abstract

A indústria de fundição desempenha um papel fundamental na manufatura global, sendo indispensável para diversos setores produtivos. Entretanto, essa atividade é responsável pela grande geração de resíduos sólidos, destacando-se a Areia Descartada de Fundição (ADF) como o passivo ambiental mais volumoso do setor. Atualmente, o descarte convencional, que é centralizado em aterros industriais e sanitários, não apenas representa um desafio logístico e econômico, mas também gera riscos ecológicos significativos. Diante desse cenário, este trabalho objetiva investigar estratégias de valorização da ADF, fundamentando-se nos princípios da Economia Circular (EC) para promover a transição do material de "resíduo" para "subproduto" de valor agregado. A metodologia adotada consistiu em uma Revisão Integrativa da Literatura (RIL), que permitiu sintetizar o conhecimento atual e identificar lacunas sobre a viabilidade técnica do reaproveitamento. Os resultados indicaram que a ADF possui elevado potencial de associação industrial, com destaque para sua aplicação na construção civil. Evidenciou-se que a substituição de agregados miúdos naturais por ADF em proporções de até 30% garante a manutenção das propriedades mecânicas e de durabilidade, atendendo aos requisitos normativos para diversos fins. Conclui-se que a reintegração desse material na cadeia produtiva ultrapassa a simples mitigação de impactos ambientais; ela consolida a sustentabilidade corporativa e reduz custos com extração de matérias-primas virgens, fechando o ciclo técnico do material e alinhando o setor às metas globais de desenvolvimento sustentável.

Mortars are among the most used materials in civil construction, and their mechanical properties are directly related to several parameters, namely structural behavior, durability, and failure mechanisms. As a result, predicting these parameters is essential for preventive and corrective diagnosis of structures composed of this material. Recently, machine learning models have been applied to improve these predictions. Until recently, such predictions were based on traditional empirical procedures, which are unable to capture the variability of material parameters. Nevertheless, as this is still an emerging research topic, many limitations and gaps remain to be investigated, such as the dependence on data structure and the appropriate selection of hyperparameters. Furthermore, most studies applying machine learning to mortars focus on additions, admixtures, or durability- and performance-related aspects, rather than on assessing the efficiency and robustness of the models themselves. In this context, this systematic and critical review aims to identify how machine learning models have been applied to predict the mechanical properties of different mortars. The main input parameters used for this prediction are discussed, and the hyperparameters of several machine learning models are critically analyzed and discussed. The results indicate that tree-based ensemble models perform better than other approaches, with XGBoost showing superior predictive performance.

A geração anual de areia descartada de fundição (ADF) resulta em impactos ambientais, sociais e econômicos. Alternativas para utilização desse resíduo são estudadas, sobretudo na construção civil (agregado miúdo em materiais cimentícios). O objetivo desse trabalho é determinar as propriedades mecânicas de argamassas com ADF. Realizou-se ensaios de tração na flexão, compressão e módulo de elasticidade dinâmico, em amostras com 30% de substituição da areia por ADF. Os resultados indicaram que a ADF reduziu a rigidez da argamassa, melhorando o seu desempenho quando aplicada como revestimento de paredes externas, geralmente submetidas às condições críticas de variações de temperatura e umidade.

A incorporação da escória de forno panela (EFP) como material cimentício suplementar tem se mostrado como uma opção interessante para reduzir o passivo ambiental gerado pelo setor siderúrgico e os impactos ambientais da indústria da construção civil. Neste sentido, identifica-se uma oportunidade em substituir a cal hidratada por EFP em argamassas mistas, considerando o alto teor de CaO desse tipo de escória. Portanto, o objetivo deste trabalho foi determinar a influência da substituição de 100% de Cal Hidratada (CH) por EFP, nas propriedades do estado fresco de argamassas mistas. Ao analisar os resultados, foi possível concluir que a presença da EFP não alterou a trabalhabilidade, além de aumentar a retenção de água em relação ao traço referência. Este comportamento pode ser justificado pela menor área superficial específica da EFP em comparação com a CH, o que manteve a trabalhabilidade mesmo com sua composição química distinta.

The use of lightweight concrete with expanded clay has increased as an alternative for reducing the self-weight of structures. Consequently, techniques that facilitate the analysis of the mechanical and elastic properties, such as ultrasonic pulse velocity (UPV), have gained relevance. Despite this, there is still a lack of studies focusing on the elastic properties of this type of concrete through UPV methods, particularly the dynamic modulus of elasticity (Ed) and Poisson's coefficient. This study aimed to determine the Ed and Poisson's coefficient of concrete containing expanded clay, based on the ASTM C597-16 standard and the stiffness matrix method. Strong correlations between static modulus of elasticity (E) and Ed were observed, with exceptions related to the stiffness matrix method. Nevertheless, this method provided the most suitable Poisson's coefficient for the material studied. The Ed values fell within the expected range, confirming the effectiveness of ultrasonic testing for lightweight concrete.

Amongst the byproducts of steel industry is ladle furnace slag (LFS), with a chemical composition similar to limes, especially in the high content of calcium oxide and hydroxides. Its binding potential is improved with finer texture, making it viable for use as a supplementary cementitious material (SCM). Therefore, this study investigated the effects of a total replacement of hydrated lime (HL) for LFS in masonry mortars, also exploring whether pozzolanic addition of metakaolin (MK) could enhance it, tested both at 28 and 180 days. The experimental results, obtained at 28 and 180 days, showed that the replacing HL for LFS improved the mechanical properties of the mortars, due to the greater amount of compounds of LFS also present in the OPC, but not in the HL, such as Fe₂O₃, Al₂O₃ and SiO₂. These findings suggest the potential of LFS for application in masonry mortar promoting strategies of circular economy.

Ladle furnace slag (LFS) is a byproduct from steel refining with high calcium oxides and hydroxides contents, making it viable as a supplementary cementitious material (SCM), enhancing microstructure and mechanical properties, particularly in mortars. Therefore, this work evaluated the replacement of 30% of ordinary Portland cement (OPC) with LFS in coating mortars, combined with a water-retaining admixture as well as the pozzolanic addition of Metakaolin (MK). The mortars followed a 1:6 (binder:aggregate) ratio, and the tests evaluated their properties in the fresh and hardened state, such as the water retention and mechanical properties, along with microstructure characterization to investigate the effects of the binder blends. At 28 days, LFS incorporation ensured water retention, less compacted matrix and greater capacity of deformation absorption, which are properties particularly beneficial for masonry mortars. MK’s pozzolanic reactions resulted in pore refinement; however, the improvements in nominal strength were not statistically significant.