[en] Glass-ceramics in the LAS (Li₂ O-Al₂ O₃ -SiO₂ ) system with high thermal shock resistance were successfully obtained using Brazilian spodumene concentrate as the main raw material (80-70 wt%). Two compositions (Li₂ O.Al₂ O₃ .nSiO₂ ) were produced with n= 2 and 4, near to the stoichiometric compositions of β-eucryptite and β-spodumene. The characteristic temperatures of parent glasses were determined by contact dilatometry, differential scanning calorimetry and heating microscopy. The crystallization mechanism and the effect of the nucleating agent (TiO₂ .2ZrO₂ ) required to promote volume crystallization in the parent glasses were investigated. Microstructural and structural changes with temperature were also evaluated by optical microscopy and X-ray diffraction. The obtained glass-ceramics presented coefficients of thermal expansion between -0.370x10^-6 and 4.501x10^-6 °C^-1 in the 22 to 700 °C range. (author)

[en] In This work compositions containing two different wastes, transparent glass bottles, TGB (50-70%), and sludge from sewage treatment plants, STP (30-50%), and pore forming, CaCO₃ (2-10%), were prepared for the production of thermal insulators. The mixed raw materials of the formulated compositions were uniaxially pressed (40 MPa) and the powder compacts were dried (110 deg C/2 h) and fired in the temperature range between 750 and 1000 deg C with holding times from 15 to 60 min. The raw materials and obtained materials were characterized in terms of their chemical, physical and microstructural properties. The results showed that is possible to produce thermal insulators from optimized compositions containing 70% TBG, 30% STP and 5% CaCO₃ and fired between 750 and 1000 deg C for 60 min. The fired materials showed porosities between 3 and 62% with thermal conductivities between 1.25 and 0.5 W/m.K and compressive strength ranging from 8.7 to 5.4 MPa. On the basis of the obtained results it can be said, in general terms, that obtained porous materials are strong candidates for structural applications such as panels for thermal insulation witch require an adequate combination of thermal conductivity, porosity and mechanical strength. (author)

[en] Thermal comfort of residential buildings has become an important factor for the performance and functional application of materials in constructive systems. In this scenario, it also takes some concepts related to sustainability, such as the recycling of industrial wastes. Many of these materials, such as rice husk ash (RHA), become interesting mineral alternatives for production of structural and/or sealing ceramics blocks with insulating properties. In this paper, ceramic samples of formulated compositions constituted of natural raw materials (clays) and rice husk ash (8 to 20 wt%) as an alternative mineral source, were appropriated prepared, extruded and then, after drying process at 110 °C, fired at 965 °C for 2 h. The results showed the feasibility of adding rice husk ash in the production of ceramic blocks with porosities in the 16 to 32% range, resulting in a considerable reduction of their thermal conductivities (up to 27%). (author)