Materials Science Forum Vol. 820

Abstract: Mill scale contains high amounts of iron and it is classified as residue Class 2 – Not Inert (ABNT NBR 10.004:2004). Considering its availability, this study aimed to investigate glass-ceramics from this residue focused on its valorization. The influence of lithium oxide and zirconia was also evaluated. Six formulations were melted at 1350 °C and obtained frits were wet ground, dried and characterized: X-ray fluorescence, X-ray diffraction, thermal differential analysis and dilatometry. Pressed bodies were dried and heat treated at 950 °C. After, crystallized samples were characterized by different techniques: X-ray diffraction, apparent and theoretical density, coefficient of thermal expansion, hardness and bending strength. Results showed that lithium oxide and zirconia significantly influenced the thermal and structural behavior of obtained glass-ceramics.

Abstract: Clayey ceramics are being traditionally fabricated in the municipal area of Campos dos Goytacazes, Rio de Janeiro, Brazil, by a mixture of different clays to attend the technical specifications. In several cases, the simple mixture of clays is not able to grantee the required properties for a given fired ceramic product. In the present work, distinct formulation using two types of clays, with or without the addition of ornamental stone waste, were investigated for the effect on the technical properties of ceramics fired at 950°C. The results indicated that at this firing temperature the ornamental stone waste was not able to act as a fluxing agent and only the linear shrinkage was effectively improved.

Abstract: The high temperature firing to process clay ceramics requires some kind of fuel, which is associated with cost and embodied energy of the final product. Saving in fuel by introducing substances with heating power represents both economical and energetical advantages. The incorporation of a fuel containing waste into the precursor clay body constitutes also an environmentally correct solution for the destination of the waste. A typical fuel-containing waste, generated in large scale, is the residual coal, which falls to the harbor yard during transfer from the cargo ship. This coal can no longer be embarked and is usually discarded in the environment. Its addition into ceramic clay is the most viable solution. Therefore, the objective of the present work is to characterize a residual coal in terms of its chemical constituents, heat power and granulometric distribution. The results indicate that the residual coal presents toxic compounds in amounts below the limits established by the environmental legislation. Its fine granulometry favors the addition to clay ceramics.

Abstract: The kaolinitic clays from Campos dos Goytacazes, state of Rio de Janeiro, Brazil, are known by their high plasticity and refractory behavior that require sintering at elevated temperatures for consolidated ceramic structures. Processing temperatures below 1000°C may also be used if the clay body contains fluxing compounds that promote lower temperature molten phases and reduce porosity. Commercial fluxes are relatively expensive but some wastes, such as those generated in industrial activities related to glass fabrication, could provide inexpensive fluxing agents. In the present work, the incorporation of up to 40 wt% of a sludge waste from the polishing stage of glass production into a Campos dos Goytacazes clay body fired at 900°C was investigated. It was found that the sludge incorporation improved both the ceramic water absorption and the mechanical strength.

Abstract: The modern concepts of civil construction for building with a maximum of 5 stores rely on structural blocks to support part of the load. These are normally hollow parallelepiped pieces made of concrete or fired ceramic. In Brazil, the abundance and easy to mine natural clay deposits favor the use of structural blocks fabricated of fired clay ceramics. Moreover, the available wood from reforestation, as fuel for the ceramic furnaces has the advantages of a less expensive and environmentally correct source of energy. Since the main property of a structural block is its compressive strength, special care should be taken in its evaluation. The ceramic industries in Campos dos Goytacazes, traditionally involved in the fabrication of simple non-structural clay bricks, are currently interested in producing structural blocks to attend large scale governmental housing programs. In order to evaluate the mechanical performance of these structural blocks, the preset work carried out a statistical study of their compressive strength by means of the Weibull analysis together with a characterization of the precursor clay body. The results indicated that the structural blocks comply with the norm and confirmed a valid number of tested specimens.

Abstract: The production of conventional bricks for housing construction is worldwide carried out with either concrete or clay ceramics. In most municipalities in Brazil, bricks are produced from less expensive local clays and fired at temperatures as low as 600°C, normally using wood as fuel. Indeed, in many regions the direct use of natural clayey soils may be sufficient to fabricate bricks with properties complying with the norms. In the present work, three clayey soils from the municipal area of Visconde de Rio Branco, state of Minas Gerais, Brazil, were characterized for their physical and chemical aspects as well as the main technological properties of ceramics fired at 700, 850 and 950°C using the different soils as precursor bodies. The results indicated that these soils are acceptable for clay ceramic fabrication but only one has the strength complying with the Brazilian norm for masonry brick fired at the investigated temperatures.

Abstract: The incorporation of industrial wastes into clayey ceramics used in civil construction is becoming a worldwide procedure not only to provide an environmentally correct destination for the waste but, in some cases, to improve the ceramic properties. The objective of the present work was to evaluate the effect of incorporation of a glass powder waste from decontamination process of fluorescent lamps into clayey ceramics. This evaluation was performed based on the technological properties of water absorption, linear shrinkage ad flexural strength. The properties evaluation was complemented by optical microscopy structural observation. The glass waste was incorporated in up to 30 wt% and specimens were uniaxially pressed at 20 MPa and fired at a relatively higher temperature of 1000°C. The results confirmed a substantial improvement of both the water absorption and the strength with glass waste incorporation into clayey ceramics.

Abstract: From the point of view of mechanical strength, ceramic materials exhibit dispersion results after being subjected to various levels of stress. However, there are no statistical surveys addressing the results efficiently. The present study aims to conduct with statistically survey, through the Minimum Lot Size, Chauvenet criterion and the Tukey range test. Specifically, the mechanical strength of red ceramic incorporated with ornamental rock waste and fired up to 700°C was analyzed, before and after degradation. The pieces were subjected to degradation of up to 1,500 hours by continuous leaching and of up to 10 months by the natural process. The results of the Tukey Test, before and after the degradation, showed statistical differences, ensuring that the data analysis was effective.

Abstract: Construction industry is the one that increases the most in Brazil, nowadays. On the other hand, this high development speed brings a concern with the destination of its leftovers. As it happens in most industrial processes, feedstock’s particles size is very important in reuse processes of brick waste and it is directly related with formed materials’ behavior. In this context, the main purpose of this study is to evaluate the influence of particle size in physical properties of specimen made of bricks’ waste through a characterization using Scanning Electronic Microscopy and X-Ray Diffraction. The specimen were made from three different selections of comminuted bricks’ particle size and then submitted to Flexural Strength tests. The results show that the material’s physical properties improve as the feedstock’s particle size decreases.

Abstract: The recycling of industrial wastes has become a worldwide practice owing to environmental and economical advantages. In the case of waste addition to clayey ceramics for civil construction, this sustainable practice may also bring technical benefits. Fluorescent lamps, today replacing incandescent lamps, generate typical glass waste that can improve the properties of clayey ceramics. The fluxing behavior of the glass waste contributes to the ceramic sintering mechanisms by reducing the porosity. In the present work, the effect of incorporation of 30 wt% of Hg-cleaned fluorescent lamps glass waste was investigated by means of microstructural analysis. Waste incorporated clayey ceramics, fired at 850 and 1100°C were analyzed by optical and scanning electron microscopy as well as by X-ray diffraction. The results revealed the microstructural mechanism responsible for the improvement of the ceramic properties.