Abstract This study aims to develop a pressed concrete roofing tile from powder technology containing basalt powder in substitution of fine sand (aggregate) for application in building covers. Specimens were submitted to technological and toxicological characterization. Hence, pressed specimens based on cement and basalt powder were analyzed. In the bending strength test, the pressed samples containing a cement:basalt mass ratio of 1:6, water content of 5% and specific pressure of 25 MPa revealed a value of 3.82 ±0.46 MPa at 28 days of curing, while the molded samples (reference) with cement:sand mass ratio of 1:5 and 15% water content revealed 1.72 ±0.86 MPa. This composition, containing cement and basalt powder, is not toxic, confirming the possibility for total replacement of sand by basalt powder. Thus, it was demonstrated that the technical viability for the proposed process and the use of basalt powder to obtain pressed flat concrete roof tile meets technical requirements and standards, compared to conventional concrete roofing tiles.

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.

In this work, discarded soda-lime-silica glass bottles and tobacco residue (after oil extraction to produce biodiesel) were prepared in different formulations to obtain glass foams. The formulated compositions were homogenized and uniaxially compacted at 40 MPa then fired at 850 ºC and 900 ºC for 60 min to investigate the effects of tobacco residue and temperature in thermal and mechanical properties of the glass foams. The results show that glass foams obtained are promising materials for applications where thermal insulation and mechanical strength are desired, with values of 0.087 W.m-1K-1 and 2.1 MPa, respectively for 45% of the tobacco residue that was added to the glass foam and fired at 850 ºC. These characteristics occur through a suitable combination of thermal conductivity and compressive strength, showing advantageous properties for applications in sustainable constructions and industrial energy efficiency.

RESUMO O presente trabalho avalia os efeitos da adição de glicerol sobre a porosidade e resistência mecânica de um material cerâmico. As amostras foram compactadas por prensagem uniaxial e submetidas a temperaturas de queima de 950 °C e 1100 °C, com taxa de aquecimento de 7 °C min-1. Foram realizados ensaios físicos e mecânicos para analisar porosidade aparente, absorção de água, retração linear e resistência mecânica a flexão. Os resultados mostram que a adição de 10% de glicerol à argila melhora principalmente suas propriedades mecânicas, podendo ser um aditivo promissor para gerar materiais cerâmicos estruturais com microestrutura mais resistente.

ABSTRACT The present work evaluates the effects of the glycerol addition on the porosity and mechanical resistance of a ceramic material. Samples were compacted by uniaxial pressing and were submitted to different sintering temperatures, 950 °C and 1100° C, with a heating rate of 7 °C min-1. Physical and mechanical analysis were performed to evaluate porosity, water absorption and linear retraction. The results show that the addition of 10% of glycerol into the clay mainly improves its mechanical properties, being able to be a promising additive to generate structural materials with more resistant microstructure.

RESUMO Neste trabalho, foram produzidas espumas vitrocristalinas a partir de vidros de garrafas descartadas e casca de arroz (3 a 25% em massa), como agente porogênico. Diferentes composições foram preparadas de maneira a se obter materiais com porosidade controlada para aplicações, nas quais o isolamento térmico e a não-inflamabilidade são os principais requisitos técnicos. Os pós de cada matéria-prima (resíduos) foram homogeneizados e as misturas foram então prensadas uniaxialmente (20 MPa). Os compactos obtidos foram queimados em diferentes temperaturas (700 – 950 °C) e tempos de patamares (30 – 120 min). As matérias-primas e as espumas vitrocristalinas produzidas foram caracterizadas de acordo com suas propriedades químicas, físicas e estruturais. Os resultados mostraram que é possível produzir espumas vitrocristalinas a partir de composições otimizadas com 85% de vidros de garrafas e 15% de casca de arroz, queimadas a 900 °C por diferentes tempos. Tais espumas vitrocristalinas apresentaram porosidade variando entre 80 e 84% enquanto a condutividade térmica e a resistência mecânica à compressão variaram entre 0,068 e 0,082 W/m.K e entre 1,1 e 1,8 MPa, respectivamente.

ABSTRACT Vitrocrystalline foams from discarded glass bottles and rice husk (3 to 25 wt%) as pore forming agent were produced in this work. Different compositions were prepared in order to obtain materials with controlled porosity in applications where thermal insulation and non-flammability are major requirements. Well-homogenized powders of the formulated compositions were uniaxially pressed (20 MPa) and the obtained compacts fired at different temperatures (700 - 950°C) and holding times (30 - 120 min). Raw materials and the obtained vitrocrystalline foams were characterized according to their chemical, physical and structural properties. The results showed that it is possible to produce vitrocrystalline foams from optimized compositions containing 85% glass bottle and 15% rice husk, fired at 900°C for different holding times. These vitrocrystalline foams presented porosity varied from 80 to 84% while the thermal conductivity and compressive strength varied between 0.068 and 0.082 W/m.K and from 1.1 to 1.8 MPa, respectively.

In this work, nanometric Al2O3 (1-5 vol.%) particles (13 nm, 100 m2/g) were added to a 19.58Li2O•11.10ZrO2•69.32SiO2 (mol%) (3.5 µm, 2.5 m2/g) parent glass-ceramic matrix to prepare composites with the purpose of studying the influence of Al2O3 on their structure, microstructure, mechanical, thermal and electrical properties when sintered by fast firing. The parent glass-ceramic was prepared by melting and fast cooling (in water) to obtain a glass frit. The resulting glass frit was milled according to a two-step procedure consisting on a dry milling stage followed by a long wet milling step down. Each composition was wet homogenized and then dried at 110 ºC for 48 h for disaggregation. The obtained powders were uniaxially pressed (100 MPa) and compacts sintered by fast firing (175 ºC/min) between 800 and 900 ºC for 30 min. The composites, with relative densities ranging from 89% to 93%, showed zircon and β-spodumene as main crystalline phases. The hardness and Young's modulus varied from 4.5 to 6.5 GPa, and from 65 to 102 GPa, respectively. The formation of β-spodumene in the obtained composites leads to reduce the CTEs, whose values ranged from 13 to 7 x 10-6 ºC-1.

Abstract In this work, compositions containing transparent glass bottles and banana leaves (desiccated and crushed), with different mass fractions (30-50%), were prepared for obtaining cellular materials for thermal insulation purposes. The formulated and prepared compositions were uniaxially pressed (10 MPa) and the compact powders fired between 700 and 850°C for 30 min in order to investigate the effect of the banana leaves on the formation of pores and on the thermal and mechanical properties of the processed glass foams. The results indicated that the obtained glass foams with porosities between 58.5 and 87.5%, compressive strength ranging between 1.17 and 3.50 MPa and thermal conductivity ranging between 0.06 and 0.15 W/mK, are potential candidates to work as thermal insulators with appropriate properties for a specific application.

RESUMO Resíduos de vidro podem ser reutilizados para o desenvolvimento de materiais alternativos. Uma opção viável são os materiais celulares para isolamentos térmicos já que, apresentando poros isolados, possuem baixa condutividade térmica, baixa densidade aparente e temperaturas de serviço mais altas que a dos materiais isolantes poliméricos. Neste trabalho, foi preparada uma suspensão aquosa com resíduos de vidro previamente moídos, Ágar-ágar (gelificante) e Emustab(r) (emulsificante), a qual foi adicionada diferentes frações de óleo de soja (50, 70 e 90% em massa). Subsequentemente, foi realizada a emulsificação do óleo vegetal no líquido da suspensão por meio de agitação em misturador mecânico de alto cisalhamento. Corpos de prova cilíndricos foram produzidos via colagem por gelificação e queimados a 700 °C/30 min. Os resultados mostraram que os vidros celulares obtidos apresentaram porosidade entre 74 e 93% com poros bem definidos e distribuídos e baixas condutividades térmicas (0,05 a 0,09 W/m.K). Tais resultados indicam que os materiais obtidos são potenciais candidatos para atuarem como isolantes térmicos, como por exemplo, painéis para revestimentos utilizados na construção civil.

ABSTRACT Glass wastes can be reused for the development of alternative materials. A viable option are the cellular materials for thermal insulation since with isolated pores they show low thermal conductivity, low density and service temperatures higher than those of the polymeric insulating materials. In this work an aqueous suspension was prepared with previously milled glass wastes, agar (gelling) and Emustab(r) (emulsifier), in which different soy oil fractions (50, 70 and 90 wt% ) were added. Subsequently, the emulsification of the vegetable oil was carried out in the liquid suspension by stirring in a mechanical mixer at high shear. Cylindrical samples were produced by gelation slip casting and fired at 700 °C/30 min. The results showed that the obtained cellular glasses had porosity between 74 and 93% with well-defined and distributed pores and low thermal conductivity (0.05 to 0.09 W/mK). These results indicate that the obtained materials are potential candidates to act as thermal insulators, such as panels for coatings used in construction.