Carolina del Roveri

Potencial geoparque de Uberaba (MG): geodiversidade e geoconservação

O Municipio de Uberaba apresenta grande potencialidade geoturistica em relacao aos seus patrimonios geologicos. As rochas igneas da Formacao Serra Geral sao encontradas em 12 atrativos geoturisticos, com destaque para as cachoeiras de Ponte Alta (40 metros de altura) e Peiropolis III (7 metros de altura). As rochas sedimentares da Formacao Uberaba foram descritas em 11 atrativos geoturisticos, destacando-se Cachoeira e Gruta do Giovane (12 metros de altura). Nas rochas sedimentares da Formacao Marilia destaca-se o afloramento da Caieira (gruta de tres metros com estalactites e estalagmites) e a Cachoeira do Vale Encantado (8 metros de altura), entre outros 8 atrativos. Apos o levantamento da geodiversidade foi realizado um diagnostico ambiental nos atrativos geoturisticos, sendo utilizado o Metodo Visitor Impact Management. Os resultados indicam que somente a Cachoeira do Vale Encantado apresenta impacto moderado, o menor quando comparado aos 22 atrativos com impacto alto ou preocupante, e 7 atrativos com impacto muito alto. Alem de definir as estrategias de manejo e monitoramento dos indicadores de impacto ambiental, o presente trabalho serve de base para que as atividades do potencial Geoparque de Uberaba (MG) sejam realizadas com responsabilidade ambiental e/ou geoconservacao.

Matéria-prima da formação Corumbataí na região do pólo cerâmico de Santa Gertrudes, SP, com características naturais para fabricação de argila expandida

This paper refers to the study of the material of the base of the Corumbatai formation (Parana Basin, Brazil) of a clay mine, which presents limits for its use in ceramic tiles in dry grinding process due to its hardness and, especially, the high content of organic matter in relation to the clay overlaid. The characterization of the raw material and the product was accomplished by organic carbon analysis, X-ray diffraction, optical microscopy and test-firing. Firing conditions were determined to get expanded clay, using fast firing static kiln and a continuous roller kiln, both from laboratory equipment, getting samples with variable density up to the limit of expansion, with density that can reach values lower than 0.5 g.cm-3 because of the formation of closed pores and an external vitreous foil which provide a high mechanical resistance to the particles.

Estudo de caracterização de argilas não plásticas da região de Poços de Caldas, MG

Pocos de Caldas e um importante centro hidrotermomineral do Brasil, o qual apresenta depositos de argilas nao plasticas para as quais nao ha registros significativos a respeito da caracterizacao direcionada destes materiais, o que prejudica estudos de aplicacao industrial. Estas argilas nao plasticas, nao aproveitadas, vem sendo armazenadas em galpoes ou a ceu aberto, o que gera um elevado custo para a industria, alem de transformar-se em um passivo ambiental. No presente trabalho realizou-se o estudo quimico-mineralogico de seis amostras de argilas de baixa plasticidade, alem da caracterizacao preliminar destas amostras quanto a granulometria, plasticidade e propriedades cerâmicas basicas, visando ampliar os horizontes das investigacoes destes materiais. Este estudo preliminar mostrou que, de maneira geral, as amostras sao compostas por minerais refratarios como caulinita e gibbsita, apresentando teores menos significativos de outras fases, como quartzo, vermiculita e illita. Juntamente as analises quimicas, estes dados permitiram o agrupamento das materias-primas em dois grupos em funcao de sua refratariedade, norteando assim, a caracterizacao posterior. Dentre as amostras, ha material com potencial uso na formulacao de massas de porcelanato, alem de uma amostra turfosa, cuja aplicacao esta relacionada a correcao de solos.

The use of nepheline as alternative source of alkalis in porcelain tiles: rheological and physical evaluation

The porcelain is a type of ceramic tile which has been contrasted for its good aesthetical, such as decorated surface, and mechanical properties, such as low water absorption and high mechanical and chemical attack resistance. The raw materials used for porcelain tiles production are mainly clay and feldspar. Feldspar is one of the raw materials responsible for the sintering during firing and it helps on the development of low porosity and high wear resistance of the ceramic piece. However, Brazil presents feldspar sources in regions distant from production centers, leading to higher cost for the porcelain tiles production. Thus, nepheline is thought as an alternative to substitute feldspar, totally or partially, since this mineral presents very similar characteristics. In order to verify the influence of this substitution to the properties of the porcelain tiles, it was necessary initially to study the influence of nepheline addition in both rheological and physical properties of the suspension. The results showed that the viscosity of the suspension increases with the addition of nepheline, as well as the apparent density of the fired piece.

UM DIAGNÓSTICO DOS CURSOS DE GRADUAÇÃO EM ENGENHARIA DE MINAS E REALIZAÇÃO DE UM COMPARATIVO COM CURSOS DE OUTROS PAÍSES COM GRANDE PRODUÇÃO MINERAL

Júlia Guimarães Sanches Maurício Guimarães Bergerman Carolina Del Roveri Resumo O curso de Engenharia de Minas sofreu uma expansão, juntamente com todo o ensino superior no país, por volta de 2005. O objetivo do presente estudo é avaliar as características dos cursos do país e realizar uma comparação com cursos de outros países com grande produção mineral. Foi feito um levantamento inicial a partir de informações disponíveis nos sites do MEC, INEP e das universidades. Como complemento, realizou-se um questionário com os coordenadores dos cursos de Engenharia de Minas do Brasil. Foram compilados ainda dados relativos à estrutura curricular e carga horária dos cursos de Engenharia de Minas dos EUA, Canadá, Austrália, Chile e África do Sul. Em relação à comparação das grades curriculares com os cursos de outros países, observou-se que no Brasil o curso possui uma maior cara horária de Tratamento de Minérios em detrimento da lavra. Nos demais países estudados, o foco das disciplinas é a lavra, já que nestes países a área de Tratamento de Minérios é assunto de outras Engenharias. Palavras-chave: Educação, Engenharia de Minas.

Study on the Influence of Water-Reducing Additives in Concretes for Civil Construction

Water-reducing additives for concretes are high efficiency dispersants that promote reduction of viscosity in suspensions, minimizing the amount of water used to hydrate the cement, thus enabling the fabrication of concrete with excellent properties. However, different forms of interaction between cement and additives are observed. In this work the properties of concrete formulated with three dosages of a polycarboxylate-based water-reducing additive and cement type CPII E-32 from two distinct manufacturers were investigated. In the experimental part, we verified the importance to use this technology justified by excellent results obtained for mechanical resistance and plasticity properties of the concretes. Through statistical analysis it was possible to point a discrete superiority in compositions using Holcim cement in function of its physical and chemical characteristics, in which the interaction process showed to be more efficient.

Use of Statistical Techniques in the Optimization of the Process "Starch Consolidation"

The Starch Consolidation method of molding technique is based on the ability of starch swell and gelatinize in water, so the green bodies are formed from suspensions, generating controlled porosity after firing; however, it is strongly influenced by gelatinization temperature, starch used, content and type of dispersant, pH and viscosity. This work involves the statistical analysis of possible relations between viscosity, content of dispersant and pH. Slurries containing alumina, water and starch were prepared, settling the solids in 40% and varying the starch content of 10, 20, 30, 40 and 50%, compared to the solids at the mixture. PH and viscosity measurements were made of the slurries as a function of added dispersant. Were obtained and analyzed measures of each parameter, using the Pearson correlation, verifying the existence of an almost perfect correlation between most of the parameters studied.

Obtaining and Characterization of Porous Bodies Obtained by Gelatinization

Porous ceramics have certain unique properties such as high toughness and resistance to heating at elevated temperatures. These properties make them products of great interest for applications on the field of filters and biomaterials. This paper proposes a new technique, called gelatinization, for processing this class of ceramics in order to obtain materials with more controlled pore size, plus a more homogeneous distribution. In order to check the efficiency of this technique, it was used as a raw material powders of calcined alumina and titania, previously characterized, mixed with unflavored gelatin, water and dispersant for holding the ceramic conformation. Three different formulations (with 40, 50 and 55% of solids content) were investigated using alumina and titania separately. The results indicated that the most suitable composition in terms of moldability was 55% of solids. It was also observed that the use of this technique to obtain bodies of high porosity is feasible; however, more detailed studies of sintering are necessary to obtain parts after firing in a close future. Due to the high porosity obtained the green, a detailed study of the sintering conditions is crucial to obtain parts with physical integrity.

Study of Processing Techniques for Nepheline Syenitic Raw Material Exploitation

Lavrinhas, a city located 234 km northeast of São Paulo, Brazil, presents syenitic rocks with high content of nepheline, whose preliminary field assessment indicated its potential to be used in the production of ceramic products. The paper aimed to study this raw material with fluxing properties and to determine the best processing methods based on mineralogy and texture, in order to achieve better removal efficiency of the nepheline. Petrographic characterization was carried out in two rock samples, as well as the particle size characterization of the untreated material, the split into fractions for magnetic separation tests and optical microscope observation of the products. In addition, chemical and particle size analysis and melting tests were performed. The latter concerned the material melting color evaluation before and after the magnetic separation, as well as its potential use in glazes and engobes, compared to a standard sample of Nepheline, and inferences for the use in porcelain masses. Preliminary tests showed that after the removal of residual iron oxide, the nepheline raw material bearer has potential to be used in the formulation of porcelain masses, replacing other fluxing materials with higher benefit.

Caracterização tecnológica para aproveitamento de matéria-prima sienítica com nefelina

Syenitic rocks with a high nepheline content near Lavrinhas (SP), 234 km northeast of the city of Sao Paulo, may be potentially useful for the production of ceramic products. Based on the mineralogy and texture of this raw material, the best methods of processing these syenitic rocks for fluxing properties are indicated here. In addition, chemical analyses and melting tests were carried out in order to evaluate the melting color before and after magnetic separation, as well as the potential use of this material in glazes and engobes, as compared to a Nepheline standard. Preliminary tests showed that after removal of superficial iron oxide, the raw material bearing nepheline has potential for use in the formulation of porcelain masses, replacing other fluxing materials which have higher added value.