EM - Escola de Minas

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Evaluation of the microstructure and micromechanics properties of structural mortars with addition of iron ore tailings.
(2023) Almada, Bruna Silva; Silva Neto, Gilberto Alves da; Prado, Dyala Fraga do; Aguilar, Maria Teresa Paulino de; Garcia, Dayana Cristina Silva; Silva, Guilherme Jorge Brigolini; Santos, White José dos
The Interfacial Transition Zone (ITZ) between the cement paste and aggregates is a region of great interest for concretes because it is the composites’ weakest region. ITZ presents a great amount of large calcium hydroxide and ettringite crystals, with the porosity being able to be up to 2.5 greater than that the rest of the paste. The microstructure, and consequently the ITZ, can be improved by mineral addition. These materials fill the pores in the composite, influence the hydration process and densify the matrix. Therefore, mineral additions, such as iron ore tailings (IOT), can modify microstructure of composites. There are few studies on the assessment of IOT heterogeneity on the microstructure and hardness of structural mortar. Thus, the present study analyzes the properties influences of four IOT types on the microstructure, porosity, and thickness of the structural mortars’ Interfacial Transition Zone (ITZ) with IOT addition, by different evaluation methods. The composites were characterized through the Scanning Electron Microscope by backscattered electrons (SEM-BSE), line scan by Energy Dispersive Spectroscopy and nanoindentation. Results presented that IOT improved particle packing and tended to reduce the ITZ. The IOT improved nucleation since it reduces the amount of anhydrous cement particles and increases the amount of calcium hydroxide particles in the cement matrix. The nanoindentation showed that IOT-added matrix presented greater hardness and indentation module. It can be concluded that the IOT heterogeneity may affect microstructural properties and that the methods presented can be good ways to evaluate the parameters.
Study of mechanical, durability and microstructural properties of cementitious composite with addition of different iron ore tailings from Brazil.
(2022) Almada, Bruna Silva; Melo, Henrique da Silva Silveira; Duarte, Marlo Souza; Aguilar, Maria Teresa Paulino de; Garcia, Dayana Cristina Silva; Silva, Guilherme Jorge Brigolini; Santos, White José dos
Brazil is the second-largest global iron ore producer in the world. Consequently, a large volume of iron ore tailings (IOTs) is generated, which is associated with environmental impacts. IOTs present potential to be used as an addition in cementitious compounds, however, few studies assess how the heterogeneity of this waste can limit its utilization as a building material. Thus, the present study aims to assess whether the heterogeneity of IOTs influences mechanical, durability, and microstructural properties when added to the cementitious composite. Four IOTs samples from different origins were collected and added to cementitious composite at 40% addition content. Composites’ mechanical (compressive strength and modulus of elasticity) and durability properties (water absorption, porosity, electrical resistivity, carbonation, and pH pore solution) were correlated to the microstructure of the IOTs. Results showed that the IOTs from different mines exhibited different physical properties and chemical/mineralogical compositions. Moreover, the higher the degree of ore processing, the lower the heterogeneity, iron content, and specific gravity. Although the IOT samples are heterogeneous, this type of tailing can be used as a filler addition in structural mortars. IOT addition tends to improve the mechanical and durability properties. Heterogeneity most significantly influenced the properties in the fresh state, durability, and microstructural properties. The microstructure of the cement matrix tends to be denser in the IOT-added with higher SSA and silica content. Was observed higher-porosity in regions close to the interfacial transition zone in the samples with coarser IOT.
Hydraulic tiles produced with fine aggregates and pigments reclaimed from iron ore tailings.
(2021) Fontes, Wanna Carvalho; Carvalho, José Maria Franco de; Silva, Keoma Defáveri do Carmo e; Silva, Guilherme Jorge Brigolini; Segadães, Ana Maria Bastos Costa; Peixoto, Ricardo André Fiorotti
Confronted with the growing ecological awareness of the consumer market, the construction industry has been seeking strategies to promote a higher insertion of waste in the production chain while contributing to the technological improvement of processes and products, as well as mitigation of social and environmental impacts and, at the same time, conferring intangible value to the product. In this sense, the present work describes how iron ore tailings (IOT) can be used in the production of cement-based (hydraulic) tiles. The physical, chemical, and mineralogical characterizations carried out demonstrated that the IOT benefciation (segregation) process resulted in a high-quality siliceous aggregate and a Fe-rich clay. The latter can be used as a pigment, whose pigmentation and cementing potentials improve with calcination and grinding. Compared to hydraulic tiles prepared with conventional materials, those obtained with the IOT-based materials displayed a pleasing appearance and the expected physical–mechanical performance.

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