Influência da gipsita no surgimento de eflorescência em telhas cerâmicas

The red ceramic industry is recognized as of major importance in Piauí State. The State capital, Teresina, is the greatest producer of this material ( production about 18 million peaces), which is used mainly for masonry sealing blocks. One of the most frequent problems in this kind of products is the efflorescence. This work has the main objective of studying the influence of gypsum addition on non-glazed tiles, by using the local industry production standards. The raw materials were characterized by FRX, DRX, TGA, DTA and AD. Extruded test specimens were made with the addition of 1, 3 and 5% of gypsum in the ceramic paste, burned at 850oC, 950oC and 1050oC and submitted to further technological tests and microestrutural analysis by the scanning electron microscope. In order to accelerate the aging of bodies of evidence, they were immersed in successive water baths and posterior drying. The reference ceramic paste showed tendency to efflorescence formation after drying and consolidated efflorescence after burning, but no affecting the technological results

Análise comparativa entre as propriedades do gesso obtido de rejeito da produção de sal e gesso comerciais

The environmental impacts, caused by the solid residues generation, are an often quoted concern nowadays. Some of these residues, which are originated from different human activities, can be fully reused, reducing the effects of the poor waste management on the environment. During the salt production process, the first formed crystals are discarded as industrial waste. This is mainly made of gypsum that is a calcium sulfate dihydrate (CaSO4.2H2O). The gypsum in question may go through a calcination process due to the plaster (CaSO4.0,5H2O) production and then the application on the cement industry. Considering the necessity of development and application for these industrial wastes, this paper aims to analyze the plaster, called Salgesso, from the gypsum that was generated during the salt production, and its use viability on the civil construction industry in order to create environmental and economical benefits. For characterization, the following experiments were performed: X-ray Fluorescence (XRF), X-ray Diffraction (XRD), thermal analysis (TG/DTG) and Scanning Electron Microscopy (SEM) with EDS. The following tests were also performed to obtain the mechanical characteristics: Thinness Modulus, Unit Mass, Setting Time and Compressive Resistance. Three commercial plasters used on civil construction were taken as references. All of these tests were performed according to the current standards. It was noticed that although there were some conflicting findings between the salt and commercial plasters in all of the studied properties, the Salgesso has its values within the standard limits. However, there is the possibility to improve them by doing a more effective calcination process. Three commercial plasters, used in construction, were used as reference material. All tests were performed according to standards in force. It was observed that although some tests present conflicting findings between the salt and gypsum plasters commercial properties in all of the studied Salgesso have values within the limits imposed by the standard, but can be improved simply by calcination process more effective

Estudo do resíduo fosfogesso na formulação de uma pasta para revestimento interno de edifícios

Universidade Federal do Rio Grande do Norte

Otimização do tempo e temperatura no processamento da gipsita oriunda dos cristalizadores da produção de sal para obter gesso de uso na construção civil

During the process of the salt production, the first the salt crystals formed are disposed of as industrial waste. This waste is formed basically by gypsum, composed of calcium sulfate dihydrate (CaSO4.2H2O), known as carago cru or malacacheta . After be submitted the process of calcination to produce gypsum (CaSO4.0,5H2O), can be made possible its application in cement industry. This work aims to optimize the time and temperature for the process of calcination of the gypsum (carago) for get beta plaster according to the specifications of the norms of civil construction. The experiments involved the chemical and mineralogical characterization of the gypsum (carago) from the crystallizers, and of the plaster that is produced in the salt industry located in Mossoró, through the following techniques: x-ray diffraction (XRD), x-ray fluorescence (FRX), thermogravimetric analysis (TG/DTG) and scanning electron microscopy (SEM) with EDS. For optimization of time and temperature of the process of calcination was used the planning three factorial with levels with response surfaces of compressive mechanical tests and setting time, according norms NBR-13207: Plasters for civil construction and x-ray diffraction of plasters (carago) beta obtained in calcination. The STATISTICA software 7.0 was used for the calculations to relate the experimental data for a statistical model. The process for optimization of calcination of gypsum (carago) occurred in the temperature range from 120° C to 160° C and the time in the range of 90 to 210 minutes in the oven at atmospheric pressure, it was found that with the increase of values of temperature of 160° C and time calcination of 210 minutes to get the results of tests of resistance to compression with values above 10 MPa which conform to the standard required (> 8.40) and that the X-ray diffractograms the predominance of the phase of hemidrato beta, getting a beta plaster of good quality and which is in accordance with the norms in force, giving a by-product of the salt industry employability in civil construction

Influência da utilização de aditivos químicos no perfil da fermentação, no valor nutritivo e nas perdas de silagens de cana-de-açúcar

Avaliou-se o efeito do uso de aditivos químicos nas perdas de matéria seca, no perfil fermentativo e no valor nutritivo de silagens de cana-de-açúcar. O experimento foi realizado em delineamento inteiramente casualizado com quatro repetições por tratamento (sete tratamentos). Os seguintes aditivos foram utilizados na confecção das silagens: controle (sem aditivo), L. buchneri, óxido e carbonato de cálcio em doses de 1,0 e 1,5% da massa verde e sulfato de cálcio a 1,0% da massa verde, diluídos em 40 litros de água por tonelada de forragem. As variáveis analisadas foram: perdas totais e gasosas, produção de efluente, recuperação de matéria seca, composição química e valor nutritivo. As menores perdas fermentativas e gasosas foram observadas nas silagens com óxido ou carbonato de cálcio, que resultaram em maior taxa de recuperação de matéria seca. da mesma forma, as silagens tratadas com estes aditivos apresentaram maior teor de carboidratos solúveis residuais e de ácido lático e reduzida fermentação alcoólica. As silagens tratadas com óxido e carbonato apresentaram, no momento da abertura, maior teor de cinzas, menor concentração de componentes fibrosos e maiores coeficientes digestibilidade da matéria seca e da matéria orgânica. O teor de proteína encontrado nessas silagens foi semelhante ao observado na forragem fresca. A ensilagem de cana-de-açúcar com L. buchneri e sulfato de cálcio possibilitou a obtenção de desempenho similar ao determinado com a silagem sem aditivos. Silagens tratadas com carbonato e óxido de cálcio apresentam maior desempenho durante o processo fermentativo.

Efeito da incorporação de soluções desinfetantes no tempo de presa, reprodução de detalhes e estabilidade dimensional de um gesso tipo IV

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise da variação da posição relativa dos dentes artificiais no arco dental em função do processamento de próteses totais mandibulares mensurada por computação gráfica

Pós-graduação em Odontologia - FOA

Avaliação da influência da incorporação de substâncias desinfetantes na resistência à compressão e à tração diametral de dois gessos tipo IV

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise de propriedades mecânicas e microscópicas de um gesso tipo IV após incorporação de derivados da clorexidina

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação das doses de cães submetidos a exames radiográficos de pulmão

This study aims to determine surface skin doses in dogs (with suspected pulmonary metastasis) submitted to chest X-rays using the technique of thermoluminescence dosimetry. Twenty seven exams from different dogs were performed at the Faculdade de Medicina Veterinária e Zootecnia da Universidade Estadual Paulista (FMVZ-UNESP/Botucatu). The doses were evaluated using thermoluminescent dosimeters of calcium sulphate doped with dysprosium (CaSO4:Dy) produced by the Instituto de Pesquisas Energéticas e Nucleares (IPEN-CNEN). The pulmonary metastasis exams are carried out in three projections, one dorsal-ventral and two lateral-lateral. During the procedures the projection thicknesses and source-skin surface distances were registered. To simulate the dog phantom the dosimeters were positioned in a cubic simulator (30x30x30 cm) of polymethylmethacrylate (PMMA) filled with water and irradiated according to the parameters of projections with the X-ray energies ranging from 45 to 70 kV. To estimate the surface skin dose the dose-response curves were obtained for X-ray energies of 50 and 70 kV using the diagnostic X-ray beam machine of the Instruments Calibration Laboratory of IPEN for doses of 1.5, 2.0, 2.5, 3.5 and 4.0 mGy. The main difficulty of this work was the dog immobilization that is reflected in poor-quality diagnostic imaging and, consequently, demands the repetition of the exams, which contributes to the increase of the doses received by the animals being studied and the clinical staff. The doses evaluated in this type of procedure are between 0.43 and 4.22 mGy. This research has shown to be extremely important for the assessment of doses involved in veterinary diagnostic radiology procedures, and as a parameter in the individual monitoring of pet’s owners who assist the animal positioning and occupationally exposed workers of the Department of Veterinary Radiology

Características químico-mineralógicas e cerâmicas da matéria-prima utilizada pelo polo cerâmico de Rio Verde de Mato Grosso, MG

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Compatibilidade entre alginato e gesso ortodônticos: capacidade de umedecimento sob influência da desinfecção do molde

The dental trade has offered dental impression and dental stone for orthodontic use ensuring accurate models. The compatibility between these materials is defined by the wetting of the model surfaces by the mixture water/stone poured over it and the influenced by the method of disinfection of model and disinfectant solution used. It was evaluated the influence of spray disinfection with sodium hypochlorite 1% on the wettability of two commercial alginate (Jeltrate ® - Dentsply and Orthoprint ® - Zhermack) at two commercial type III gypsum (Rio ® - ME and AOBussoli Orthogesso Orthogesso ®-SA). Twenty models were fabricated for each type of alginate, which were divided into two groups (water and sodium hypochlorite), receiving respectively water and sodium hypochlorite 1% spray. Each group of models was then further divided into two subgroups, and on their surface were poured 2 ml of type III gypsum (Gesso Rio® or Orthogesso®). Reached the final setting of the gypsum specimens were sectioned vertically and medially, settled water with sandpaper No. 400 and mounted on suitable device for reading (in the right and left) of the contact angle Carl Zeiss microscope (precision, 001). The results were submitted to ANOVA and founded statistical significance for solutions used. It was concluded that sodium hypochlorite spray improved wettability of alginates studied.

Cimentos bioativos injetáveis funcionalizados com peptídeo osteogênico para reparação óssea

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Biocompatibility and setting time of CPM-MTA and white Portland cement clinker with or without calcium sulfate

To evaluate the biocompatibility and the setting time of Portland cement clinker with or without 2% or 5% calcium sulfate and MTA-CPM. Twenty-four mice (Rattus norvegicus) received subcutaneously polyethylene tubes filled with Portland cement clinker with or without 2% or 5% calcium sulfate and MTA. After 15, 30 and 60 days of implantation, the animals were killed and specimens were prepared for microscopic analysis. For evaluation of the setting time, each material was analyzed using Gilmore needles weighing 113.5 g and 456.5 g, according to the ASTM specification Number C266-08 guideline. Data were analyzed by ANOVA and Tukey's test for setting time and Kruskal-Wallis and Dunn test for biocompatibility at 5% significance level. Histologic observation showed no statistically significant difference of biocompatibility (p>0.05) among the materials in the subcutaneous tissues. For the setting time, clinker without calcium sulfate showed the shortest initial and final setting times (6.18 s/21.48 s), followed by clinker with 2% calcium sulfate (9.22 s/25.33 s), clinker with 5% calcium sulfate (10.06 s/42.46 s) and MTA (15.01 s/42.46 s). All the tested materials showed biocompatibility and the calcium sulfate absence shortened the initial and final setting times of the white Portland cement clinker

Influência da temperatura de calcinação do fosfogesso no desempenho de cimentos supersulfatados

The supersulfated cement (CSS) basically consist of up to 90% blast furnace slag, 10-20% of a source of calcium sulfate and a small amount of alkali activator, covered by European standard EN 15743/2010. Because of this SSC are considered "green cement" low environmental impact. The source of calcium sulfate used in the preparation of CSS can be obtained from natural sources, such as gypsum or from alternative sources (industrial products), such as phosphogypsum. The phosphogypsum is a by-product of the fertilizer industry, used in the production of phosphoric acid. In this process the phosphate rock is treated with sulfuric acid to give as the major product phosphoric acid (H3PO4), gypsum and a small amount of hydrofluoric acid. The chemical composition of gypsum is basically calcium sulfate dihydrate (CaSO4.2H2O), similar to gypsum, because it can be used in this type of cement. To become anhydrous, the calcination of gypsum is necessary. The availability of the source of calcium sulfate to react with the slag is dependent on its solubility that is directly related to its calcination temperature. The solubility of the anhydrous gypsum decreases with increasing calcination temperature. This study investigated the influence of temperature of calcination of phosphogypsum on the performance of CSS. Samples were prepared with 10 and 20% of phosphogypsum calcinated at 350 to 650 ° C using KOH as an alkaline activator at three different concentrations (0.2, 0.5 and 0.8%). The results showed that all mortars presented the minimum values required by EN 15743/2010 for 7 and 28 days of hydration. In general CSS containing 10% phosphogypsum showed slightly better compressive strength results using a lower calcination temperature (350 °C) and curing all ages. The CSS containing 20% of calcined gypsum at 650 °C exhibit satisfactory compressive strenght at 28 days of hydration, but at later ages (56 to 90 days) it strongly reduced. This indicates that the calcination temperature of phosphogypsum has a strong influence on the performance of the CSS.