Abstract One of the solutions in civil construction to increase the life cycle of buildings is the ventilated facade due to its technical characteristics. Large porcelain tiles are used as a coating in this system, raising questions about its performance. This study used real size porcelain tiles (590 mm × 1190 mm) for pressure tests to evaluate the deformation suffered by the material at different pressure points, according to NBR 10821. In addition, the strength of the glass fiber-reinforced ceramic tiles has been tested against the impacts of rigid and soft bodies in a hidden clamp ventilated system, according to NBR 15575. Due to the wind, the system presented maximum deformation of 1.7 ±0.4 mm. When subjected to impacts, the system functioned within the norm for hard body strikes (20 J), meeting the requirements against minor proportions and wind pressures of up to 1480 Pa. Unsatisfactory performance when impacted by a soft body was observed. Such results show that the system needs to improve regarding resistance to major impacts.

Abstract In Brazil, the production of each ton of steel generates approximately 621 kg of waste and direct co-products. One of the components that generates a high amount of waste is the refractory material used in the steel process. So, in this study, the possibility of using MgO-C refractory waste from steel casting pots after their deterioration for the formation of chemically bonded phosphate ceramics was investigated. This work aims to study the recovery of industrial solid waste from MgO-C refractories by determining the processing conditions necessary to obtain magnesium phosphate ceramics. Three mean particle size of the waste and three potassium monophosphate:MgO ratio in the mixture were adopted. All mixtures showed the formation of the K-struvite phase and a strong relationship between the compressive strength and porosity properties. The highest compressive strength value obtained, 7.51 ± 0.24 MPa, is sufficient for use in several areas of engineering. It was also possible to statistically represent, using a quadratic model, the variation in porosity in relation to the phosphate content and particle size of the waste, obtaining porosities ranging from 14% to 25%. Taking into account this study used a waste, the evaluation of its environmental impact assumed an important role. The waste showed no appreciable toxicity, while some samples W3-20 showed toxicity to Allium cepa L. and Artemia salina. Considering the presented properties, the obtained material could be used as a structural block, filters, support for catalysts, and repair element for cement-based structures and roadways.

RESUMO Cenosfera é um sub-produto da combustão do carvão que apresenta interessantes propriedades para ser usado na produção de materiais cimentícios, tais como estrutura oca, baixa densidade, baixa térmica condutividade e notável estabilidade térmica. Além disso, ela mostra reatividade pozolânica na cura térmica. Entretanto, o potencial da cenosfera para o desenvolvimento de materiais de construção únicos não têm sido completamente investigados, permanecendo obscura para plantas de energia e no campo da construção. Este estudo investigou o emprego de cenosfera na substituição parcial à areia para a obtenção de materiais cimentícios de baixo peso. A cenosfera de uma planta de energia Brasileira foi química e fisicamente caracterizada e a viabilidade de seu uso em argamassas e concretos foi investigado. Foi descoberto que a cinza volante da planta de energia é composta de aproximadamente 0,2% de cenosfera. Além disso, a cenosfera exibe tamanho de partícula que varia de 30 a 300 µm e era adequada para uso como agregado fino em concreto. Concretos com 33, 67 e 100% de substituição de agregados finos pela cenosfera de resíduos foram produzidos. Concreto baseado na cenosfera de alto desempenho apresentou resistência de até 70 MPa e densidade tão baixa quanto 1500 kg • m-3. Em comparação com misturas de referência, a aplicação da cenosfera como agregado fino melhorou a resistência específica do concreto de alta resistência, mantendo propriedades mecânicas equivalentes.

ABSTRACT Cenosphere is a coal combustion by-product that presents interesting properties to be used in the production of cementitious materials, such as hollow structure, low density, low thermal conductivity and notably thermal stability. In addition, it displays pozzolanic reactivity under thermal curing. However, the cenosphere potential for the development of unique construction materials has not been fully investigated, remaining obscure for both power plants and the construction field. This study investigated the employment of waste cenosphere in partial substitution to sand for the obtainment of high-strength lightweight concrete materials. Cenosphere from a Brazilian power plant was chemically and physically characterized and the feasibility of its use in concretes was investigated. It was discovered that the power plant’s fly ash is composed of approximately 0.2% of cenosphere. In addition, the cenosphere displayed size ranging from 30 to 300 µm and were suitable for use as fine aggregate in concrete. Concrete with 33, 67, and 100% fine aggregate replacement by the waste cenosphere was produced. Cenosphere-based high strength concrete presented strength higher than 70 MPa and density as low as 1500 kg • m-3. Compared to mixes of reference, cenosphere application as fine aggregate improved the specific strength of high-strength concrete while maintaining equivalent mechanical properties.

RESUMO Este trabalho investigou o efeito da adição de resíduo de vidro para fabricação de cerâmica de alvenaria. Foram conformados corpos-de-prova cilíndricos de 27 mm de diâmetro por 45 mm de altura, a partir da massa padrão de uma indústria de cerâmica vermelha e outras 3 formulações (5, 10 e 20%) com incorporação de vidro, baseado em estudos apresentados na literatura. O tratamento térmico foi realizado em forno mufla em 3 temperaturas (800, 900 e 1000 °C). As propriedades tecnológicas avaliadas foram: retração de secagem e de queima, absorção de água, perda ao fogo e resistência mecânica à compressão. Foi possível observar que a retração de secagem baixou de 7,9 para 5,9% com o aumento do teor de vidro adicionado. A adição de resíduo de vidro à massa cerâmica não interferiu significativamente na retração de queima a 800 e 900 °C, mas aumentou significativamente a 1000 °C, assim como a absorção de água foi reduzida consideravelmente a 1000 °C. A adição de resíduo de vidro reduziu a resistência à compressão das peças cerâmicas em até 4,4 MPa, mas os valores encontrados ficaram dentro do estabelecido por norma. A composição com adição de 20% de resíduo de vidro sinterizada a 900 °C alcançou 6 MPa, valor superior ao 1,5 MPa estabelecido por norma a blocos de vedação. A 1000 °C foi observada a ocorrência de overfiring, que leva ao surgimento de bolhas e deformação. A adição de até 20% de resíduo de vidro à massa cerâmica para alvenaria sinterizada a 900 °C apresenta valores aceitáveis pela norma brasileira, das propriedades tecnológicas avaliadas, com a vantagem de reduzir a tendência ao surgimento de trincas de secagem e à variação dimensional, além de contribuir para a redução de uso de matérias-primas virgens e de se dar um destino racional a um resíduo.

ABSTRACT This work investigated the effect of the addition of glass waste to the manufacture of masonry ceramics. Was conformed cylindrical samples with 27 mm in diameter by 45 mm in height were made from the standard mass of a hard clay ceramic industry and other 3 formulations (5, 10 and 20 %) with glass incorporation, based on studies presented in the literature. The heat treatment was carried out in a muffle at three temperatures (800, 900 and 1000 °C). The technological properties evaluated were: linear drying shrinkage and linear firing shrinkage, water absorption, fire loss and mechanical resistance to compression. It was observed that the drying retraction decreased from 7.9 to 5.9 % with the increase of the glass content added. The addition of glass waste to the ceramic mass did not significantly interfere with the retraction of burning at 800 and 900 °C, but increased significantly at 1000 °C, as well as water absorption was reduced considerably at 1000 °C. The addition of glass waste reduces the resistance to compression of the ceramic pieces by up to 4.4 MPa, but the values found were within the established by norm. The composition with addition of 20 % of sintered glass waste at 900 °C reached a value of 6 MPa, value greater than 1,5 MPa for standard to hollow ceramic block for non-load-bearing. At 1000 °C was observed the occurrence of overfiring, which leads to the appearance of bubbles and deformation. The addition of up to 20 % of glass residue to the ceramic mass for sintered masonry at 900 °C presents values acceptable by the Brazilian standard, of the technological properties evaluated, with the advantage of reducing the tendency to cracks and dimensional variation, besides contributing to the reduction of the use of virgin raw materials and of giving a sustainable destination to a waste.

This work aims to evaluate the influence of a Li2O-ZrO2-SiO2-Al2O3 (LZSA) glass-ceramic on the mechanical behavior of alumina. Composites were prepared from alumina with three different particle sizes and 7 to 21 vol% of an LZSA glass-ceramic composition (11.6Li2O-16.8ZrO2-68.2SiO2-3.4Al2O3,). Specimens were obtained by uniaxial pressing. The optimum sintering temperature and holding time were found to be different for each composite. Structural characterization (bulk density and crystalline phases); mechanical characterization (flexure strength, elastic modulus, fracture toughness, and fracture energy); and microstructural analyses were carried out. Fine-grained alumina-based composite containing 21 vol% of glass-ceramic (1470 ºC and 3 h holding time, 2.0% porosity) showed a fracture toughness of 4.93 MPa·m0.5, an elastic modulus of 210 GPa, a fracture energy of 57 J·m-2, and a flexural strength of 170 MPa, in very good agreement with values reported by the literature. An increase of 37-177% in the fracture energy due to 21 vol% LZSA addition in the alumina was achieved for the range of grain size obtained in this work. Even though the final composition included a glassy component, the observed mechanical properties confirmed the effectiveness of the crystalline phases that were formed from LZSA glass-ceramic in reducing the propagation of cracks. The results showed that the addition of the LZSA glass-ceramic improved the mechanical properties of alumina.

In the southern of Brazil the coal is composed of a large amount of pyrite (FeS2), an environmental problem for this region because the pyrite turns a waste. This work investigated the behavior of pyrite in CO2 and N2 atmospheres, aiming to identify better thermal treatment conditions of the pyrite waste that favor obtaining a material with magnetic properties. The results show that the samples treated in both conditions presented hysteresis and some magnetic properties. The best results were obtained from N2 because it is an inert gas, avoiding the pyrite oxidation and, consequently, favoring a major amount of pyrrhotite. The X-ray diffraction analyses showed that partial thermal decomposition of the pyrite occurs at 600 ºC. The total decomposition was reached at 800 oC and the pyrrhotite phase was obtained. Such findings are relative new and can help enhance the utilization of pyrite, contributing to the environmental sustainability of the coal mining industry.

The aim of this study was to evaluate the effect of an 11.6Li2O-16.8ZrO2-68.2SiO2-3.4Al2O3 (LZSA) glass ceramic on the grain growth of alumina obtained by pressureless sintering. Three contents of the LZSA glass ceramic (7, 15, and 21 vol%; mean particle size of 1.52 µm) and three types of alumina (mean particle sizes of 0.5, 1.7, and 2.8 µm) were used. The powder compositions were formed by cold pressing. The samples (5 mm × 5 mm × 13 mm) were sintered in an optical dilatometer. The grain size and morphology were evaluated by scanning electron microscopy. The results show that elongated alumina particles were obtained for the investigated composites compared with pure alumina because of the LZSA addition. The grain growth of alumina was less pronounced at higher LZSA contents. High relative densities were obtained for higher LZSA contents at lower temperatures and holding times compared with pure alumina.

RESUMO A cinética de crescimento da camada superficial cristalizada em um vidro de composição do sistema LZSA, 11,7Li2O·12,6ZrO2·68,6SiO2·7,1Al2O3 (% massa), foi estudada. Para a produção do vidro, utilizou-se matérias-primas comerciais (Li2CO3, ZrSiO4, SiO2, Al2O3), as quais foram homogeneizadas e fundidas a 1550 °C por 120 min e então vazadas em molde metálico. Amostras do vidro obtido foram seccionadas e submetidas a tratamentos térmicos em diferentes temperaturas (825–925 °C) e tempos (30–150 min) para formação e crescimento da camada cristalina. Seções transversais das amostras tratadas termicamente foram lixadas e polidas, tal que imagens das camadas cristalizadas pudessem ser visualizadas e medidas por microscopia. Os resultados mostraram que é possível obter vidros do sistema LZSA com camadas cristalizadas contendo principalmente espodumênio-β e silicatos de zircônio e lítio, de espessuras entre 13 e 665 µm, as quais crescem com velocidades entre 0,4 e 4,8 µm/min no intervalo de temperatura estudado.

ABSTRACT Growth kinetics of crystallized surface layer in a LZSA glass composition, 11.7Li2O·12.6ZrO2·68.6SiO2·7.1Al2O3 (wt%), was studied. For the production of the LZSA glass, it was used commercial raw materials (Li2CO3, ZrSiO4, SiO2, Al2O3) which were mixed and melted at 1550 °C for 120 min and then poured into a metallic mold. Samples of the obtained glass were cut and subjected to heat-treatments at different temperatures (825 - 925 °C) and times (30 - 150 min) for formation and growth of crystalline layer. Cross-sections of the heat-treated samples were ground and polished such that images of the formed crystallized layers could be visualized and measured by microscopy. Results showed that it is possible to obtain LZSA glasses with crystallized layers formed by β-spodumene, zircon and lithium silicate, which present thicknesses between 13 and 665 µm and grow at rates varying from 0.4 to 4.8 µm/min in the studied temperature range.

This work evaluated the water absorption of glazed porcelain stoneware ceramic tiles using three different methods. Two methods were based on a procedure of boiling in water, specified by standards ISO 10545 and ASTM C373, and the third was the vacuum method proposed by the standard ISO 10545. The three products produced under the three different firing conditions were tested according to a 22 factorial design, with intervening factors of the boiling time and immersion time for the methods involving boiling, and of pressure and immersion time for the vacuum method. The maximum saturation of the plates was evaluated by helium gas pycnometry testing. The results showed that no sample saturation occurs in the boiling water absorption test performed according to the conditions established by standards ISO 10545 and ASTM C373. The values of open porosity, using the method of helium gas picnometry, showed absolute values of saturation higher than those presented by the water absorption measured according to the current standards. Thus, the results showed that the current methods for determining the water absorption of glazed porcelain stoneware ceramic tiles do not guarantee the complete saturation of the plates and, therefore, they are not able to correctly measure this property.

The aim of this work was to experimentally evaluate the use of calcium carbonate as a pore-generating agent in ceramic compositions. Compositions that contained 50% kaolin, 20% limestone, and different concentrations of quartz and feldspar were prepared by uniaxial pressing. Samples were heat-treated at a heating rate appropriate to induce calcium carbonate degassing, and they were then sintered at 800, 900, and 1050 ºC. Tests of X-ray fluorescence, thermogravimetric analysis, porosimetry, and air permeation were performed. The composition (wt%) that contained 50% kaolin, 20% limestone, 20% feldspar, and 10% quartz and heat treated at 1050 ºC (k1 = 1.73×10-13 m² and k2 = 1.00×10-8 m) showed the highest level of permeability among the investigated samples. Fluid dynamics simulations showed that the prepared samples would exhibit a pressure drop greater than the range desired for applications that involve the filtration of aerosols, but alternatively would be suitable as substrates for asymmetric membranes in microfiltration applications.

Fiber-reinforced concrete represents the current tendency to apply more efficient crack-resistant concrete. For instance, polyethylene terephthalate (PET) is a polyester polymer obtained from recyclable bottles; it has been widely used to produce fibers to obtain cement-based products with improved properties. Therefore, this paper reports on an experimental study of recycled-bottle-PET fiber-reinforced concrete. Fibers with lengths of 10, 15 and 20 mm and volume fractions of 0.05, 0.18 and 0.30% related to the volume of the concrete were used. Physical and mechanical characterization of the concrete was performed, including the determination of compressive strength, flexural strength, Young's modulus and fracture toughness as well as analysis using mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Flexure and impact tests were performed after 28 and 150 days. No significant effect of the fiber addition on the compressive strength and modulus of elasticity was observed. However, the Young's modulus was observed to decrease as the fiber volume increased. At 28 days, the concrete flexural toughness and impact resistance increased with the presence of PET fibers, except for the 0.05 vol.% sample. However, at 150 days, this improvement was no longer present due to recycled-bottle-PET fiber degradation in the alkaline concrete environment, as visualized by SEM observations. An increase in porosity also has occurred at 365 days for the fiber-reinforced concrete, as determined by MIP.

Ion exchange method was employed by means of surface modification of the glass powders of LZSA (Li2O-ZrO2-SiO2-Al2O3) system submitted to a 70wt% NaNO3/30wt% NaSO4 bath salt followed by a heat treatment. Chemical analysis by X-ray fluorescence was used to evaluate the efficiency of ion exchange, while optical dilatometry was employed to evaluate sintering of compacts. Evaluation of the structure of sintered bodies was made by scanning electron microscopy. Substitution of Li+ ions by Na+ ions on the surface of powders during heat treatments of 450 and 600 ºC for 2-10 h promoted an increase in densification of the sintered bodies.

The LZSA glass-ceramic system (Li2O-ZrO2-SiO2-Al2O 3) shows interesting properties, such as good chemical resistance, low thermal expansion, high abrasion resistance, and a low dielectric constant. However, in order to obtain a high performance material for specific applications, the sintering behavior must be better understood so that the porosity may be reduced and other properties improved. In this context, a sintering investigation for a specific LZSA glass-ceramic system composition was carried out. A 18.8Li2O-8.3ZrO2-64.2SiO2-8.7Al 2O3 glass was prepared by melting the solids, quenching the melt in water, and grinding the resulting solid in order to obtain a powder (3.68 μm average particle diameter). Subsequently, the glass powder was characterized (chemical analysis and determination of thermal properties) and the sintering behavior was investigated using optical non-contact dilatometry measurements. The results showed that the crystallization process strongly reduced the sintering in the temperature interval from 785 to 940 °C, and a maximum thermal shrinkage of 15.4% was obtained with operating conditions of 1020 °C and 180 minutes.