EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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4 resultados
Resultados da Pesquisa
Item 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 dosThe 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.Item Investigation on mechanical and microstructural properties of alkali-activated materials made of wood biomass ash and glass powder.(2021) Silva, Guilherme Jorge Brigolini; Santana, Vanessa Pereira; Wójcik, MartaThe possibility of the application of biomass fly ash (BFA) as a precursor material for the synthesis of alkaliactivated materials (AAM) is presented in this paper. Glass powder (GP) was tested as an additional substrate in a synthesis process. Different mixtures of samples were produced: four mixtures using only BFA for different NaOH concentrations and nine mixtures where BFA was partially replaced by the GP. Three different NaOH concentrations were applied here. Compressive and flexural strength after 7 and 14 days were performed. The microstructure and the chemical composition of samples were obtained. The results show that the compressive and flexural strength of materials increased with the increase of NaOH concentration and the decrease of the GP content in a mixture. The samples were also characterized by the high porosity with some voids and microcracks. The poorly dissolved BFA particles were also noted in a matrix.Item Factors affecting the specific heat of conventional and residue-based mortars.(2020) Mendes, Júlia Castro; Barreto, Rodrigo Rony; Castro, Arthur Silva Santana; Silva, Guilherme Jorge Brigolini; Peixoto, Ricardo André FiorottiThe present work investigates the specific heat of cement-based composites and the factors influencing it. To this purpose, coating mortars with Portland cement and hydrated lime were investigated, along with four types of aggregates: river sand, friable quartzite (QTZ), steelmaking slag (SLG), and iron ore tailings (IOT). Initially, the aggregates were characterised chemically and physically. Subsequently, the mortars were evaluated according to their physical and thermal properties. Adiabatic calorimetry was used to measure the specific heat of the samples in two conditions: oven-dried and saturated. The advantages and limitations of the method were discussed. Results showed that the microstructure of the mortars was more significant to the resulting specific heat than their chemical composition or density. Mortars with high specific heat and density, such as those with IOT and SLG, have great potential as sensible heat storage. Therefore, for application purposes, the specific heat should preferably be obtained through techniques that maintain the structure of the composite mostly intact, such as adiabatic calorimetry.Item Iron ore tailing-based geopolymer containing glass wool residue : a study of mechanical and microstructural properties.(2019) Silva, Keoma Defáveri do Carmo e; Santos, Letícia Figueiredo dos; Carvalho, José Maria Franco de; Peixoto, Ricardo André Fiorotti; Silva, Guilherme Jorge BrigoliniThis work presents an evaluation of the application of iron ore tailing as primary precursor material to geopolymer production. Glass wool residue from the iron ore industry was also included as a blend material. Four mixtures of geopolymers were produced: one mixture using only iron ore tailing; three mixtures where the iron ore tailing was replaced by the glass wool residue, with a substitution ratio of 10%, 20% and 30% (in mass). Furthermore, three different grinding times and three NaOH solution concentration were applied. Compressive strength and flexural strength tests were performed in prismatic specimens at 7-days, and the microstructural analysis of the fragments was obtained by SEM analysis. QXRD analysis based on the Rietveld’s refinement method and TG/DTA analysis was applied for all specimens. The results showed the synthesis of a zeolite phase in all specimens, and the SEM micrographs showed a transformation process of the glass wool residue. Finally, high mechanical performances were found to the iron ore tailing-based geopolymer, reaching values higher than 100 MPa for compressive strength and 20 MPa for flexural strength. The obtained values are related to the grain packing improvements, geopolymerization products, and the glass wool residue working as a supplementary precursor material to the geopolymerization reaction. The result points to the potential of iron ore tailing and glass wool residue to geopolymers studies and application.