Fast-firing Cycle Research Articles

Utilization of marble waste as a sustainable replacement for calcareous in the manufacture of red-firing wall tiles

Marble waste generated in large amounts in the ornamental rock industry needs to be disposed of in a sustainable way and valorized. In this respect, this work analyzed the use of marble waste as a sustainable raw material in manufacturing red-firing wall tiles, replacing the natural calcareous material by up to 15 wt%. For this purpose, four red-firing wall tile pastes containing marble waste were pressed into rectangular pieces and fired between 1100 °C and 1180 °C using a fast-firing cycle. The red-firing wall tile specimens produced were tested to determine their technical properties (linear shrinkage, water absorption, apparent density, and three-point flexural strength), phase analysis by XRD, and microstructural analysis by SEM. The densification behavior and technical properties of these specimens were influenced by the incorporation of marble waste and firing temperature. The results showed that this waste is highly compatible for the manufacture of high-quality red-firing wall tiles, meeting the normative requirements (water absorption and flexural strength) of group-BIII of ISO 13006. The marble waste may fully replace the natural calcareous used in the manufacture of this type of tile material, contributing to its recycling and valorization with positive repercussions for both the ornamental rock and ceramic industries.

Potentiality for using paper sludge waste in the manufacture of red wall tiles

Paper sludge waste is produced on a large scale by the paper industry and causes significant environmental impacts. This work investigates the potential of paper sludge waste incorporation as an alternative raw material into a red wall tile formulation, replacing traditional limestone material by up to 5 wt%. Red wall tile pieces containing paper sludge waste were produced by uniaxial dry pressing and fired at 1170°C using a fast-firing cycle. Technical properties of the fired wall tile pieces have been determined. The development of the fired microstructure was determined by scanning electron microscopy. It was found that water absorption was 17.15–18.31%, flexural strength was 15.77–16.17 MPa, linear shrinkage was 2.88–3.22% and apparent density was 1.76–1.81 g/cm3. Therefore, the results indicated that the paper sludge waste, in the range of up to 5 wt%, can produce red wall tiles (group BIII in the ISO 13006 standard). At the same time, this application helps minimise the environmental impacts caused by the paper industry.

Effect of fluxing raw materials on moisture expansion of monoporosa wall tile bodies

In the production of wall tiles, trends are moving toward larger-format wall tiles. Moisture expansion of larger-format wall tiles is one of the most important technological parameter that determine the quality of their service life. Clay, kaolin, quartz, carbonate and less fluxing materials are generally used in monoporosa tile recipes. In this study, alkali containing raw materials such as perlite, rhyolitic tuff, granite and nepheline syenite, were used instead of quartz and kaolin in the recipes. The investigated bodies are fired under industrial fast firing cycle at 1150 °C—50 min. Firing shrinkage, water absorption and color values (L*, a*, b*) of alkaline raw materials and bodies were measured. Thermal expansion coefficient and moisture expansion values of the bodies were determined by dilatometer and the sintering behavior of the representative formulations was evaluated using a double-beam non-contact optical dilatometer (ODHT). Phase and microstructural analyses were performed by XRD and SEM, respectively. As a result, the analytical data obtained from this study revealed that the alkaline/flux materials which have more or less similar chemical compositions, represent distinctly different physico-mechanical behavior. According to the petrographical examinations, whereas the holocrystalline textured alkaline materials such as nepheline syenite and granite decrease moisture expansion, the use of amorphous-glassy textured raw materials such as perlite and rhyolitic tuff increase moisture expansion in monoporosa tile body manufacturing. Using of the alkali raw materials as a partial replacement of quartz also enables the development of lower thermal expansion bodies.

The crystallization and structure features of glass within the K2O–MgO–CaO–Al2O3–SiO2-(BaO) system

The effect of the BaO addition on the microstructure and structure of the glasses from the K2O–MgO–CaO–Al2O3–SiO2-(BaO) system was investigated in this study. The results were obtained by testing the crystallization capability of the glasses during the fast-firing cycle. Thermal analysis proved a high tendency to crystallize the tested glasses/frits. X-ray analysis showed the presence of diopside and anorthite as the main crystalline phases in all glazes obtained from the tested glasses. Microscopic observations showed that barium oxide introduced in the range of 0.4–2.1 mol% into the examined system strongly influences the number and size of crystalline phases. The introduction of 2.1 mol% BaO into the composition also resulted in crystallization of celsian. The thermal characteristic of the glasses was carried out using differential scanning calorimetry (DSC) and the crystalline phases were determined by X-ray diffractometry. The glaze microstructure was investigated by scanning (SEM) and transmission electron (TEM)microscopy. Additional information on the structure of frits was derived from mid-infrared (MIR) and Raman spectroscopy.

Novel light-weight glass-ceramic proppants based on frits for hydraulic fracturing process

High strength proppants were always in demand for hydraulic fracturing techniques used in unconventional reservoirs for oil and gas extraction processes. To support this concept, relatively low-alumina content glass-ceramic proppants based on the system Fe2O3–TiO2–MgO–CaO–SiO2–Al2O3 have been prepared by using frit, kaolin, and bentonite in a glaze formulation. By deposition of glaze drops on porous ceramic tile, a semi-dry proppant beads were obtained. Different frit compositions of aluminum oxide replacing calcium oxide were used to obtain highly sintered proppants with a robust glassy matrix at 1100 °C in a fast firing cycle. The microstructure by scanning electron microscopy (SEM) and the phase structure by X-ray diffraction (XRD) were investigated. The results revealed the formation of two main phases; cristobalite and calcium aluminum silicate in addition to the other two phases of mullite and Diopside ferrian in some samples. By evaluating the employed fabricated ceramic compositions as high conductivity and high strength proppants for hydraulic fracturing process it was found that all samples exhibited competitive properties according to American Petroleum Institute standards (API RP 19C Standard) for proppants criteria. Crushing loss under 7500 psi closed pressure was (from 1.5% to 6.7%), the weight loss by acids attack was (from 0.001% to 0.07%), sphericity and roundness were (0.9) in addition, the apparent and bulk densities were (from 2.51 to 2.58 g/cm³) and (from 1.46 to 1.50 g/cm³), respectively.

Influence of SrO content on microstructure and crystallization of glazes in the SiO2\u2013Al2O3\u2013CaO\u2013MgO\u2013K2O system

The effect of the SrO addition on the microstructure and structure of the glazes from the SiO2–Al2O3–CaO–MgO–K2O system was investigated in this study. The results were obtained by testing the ability of the frits crystallization, the stability of the crystallizing phases during the single-step fast-firing cycle depending on their chemical composition and the effect of addition of strontium oxide. Differential scanning calorimetry (DSC) curves showed that all glazes crystallized, and diopside and anorthite were mainly identified as dominant phases in the obtained glazes, while the size and amount of each depended on the amount of SrO introduced. The thermal characteristic of the frits was carried out using DSC, and crystalline phases were determined by X-ray diffractometry. The glaze microstructure was investigated by scanning electron microscopy and transmission electron microscopy. Additional information on the microstructure of frits was derived from spectroscopic studies in the mid-infrared range.

Use of Firewood Ash Waste in Electrical Siliceous Porcelain

The use of firewood ash waste for the production of electric porcelain can represent an important technological and environmental alternative for the final disposal of this abundant solid waste material. This work aims to study the effect of replacing of sodium feldspar (albite) for firewood ash waste in electrical siliceous porcelain formulation. The firewood ash waste was obtained from a ceramic plant located in south-eastern Brazil (Campos dos Goytacazes-RJ). For this purpose, siliceous porcelain formulations containing up to 4.2 wt.% of firewood ash waste as a replacement for sodium feldspar were prepared. Disk specimens were pressed and fired at 1300 °C using a fast-firing cycle. The porcelain specimens were tested to determine their technical properties (linear shrinkage, water absorption, apparent porosity, apparent density, tensile strength, and electrical resistivity). The results indicated that test specimens containing up to 4.2 wt.% of firewood ash waste have high potential for use as electrical siliceous porcelain material. Thus, an alternative use of firewood ash waste is proposed, which can be converted into economic gain and also contribute for the environmental sustainability.

Application of grits waste as a renewable carbonate material in manufacturing wall tiles

This work focuses on the reuse of grits waste, from cellulose industry, as a raw material to replace traditional carbonate material in ceramic wall tiles. Wall tile formulations bearing up to 15 wt% of the grits waste were prepared for replacement of calcareous. The tile manufacturing route consisted of dry powder granulation, uniaxial pressing, and firing at temperatures ranging from 1100 °C to 1180 °C by using a fast-firing cycle. The wall tile specimens were tested to determine their physical and mechanical properties (linear shrinkage, water absorption, apparent porosity, apparent density, breaking strength, and flexural strength). The firing behavior, phase transformations, and microstructure were evaluated by dilatometry, XRD, and SEM. The results showed that the fired wall tile specimens are composed of anorthite and quartz, as major mineral phases, and mullite as a minor phase. It was found that the grits waste had a positive influence on the properties and microstructure of the wall tile specimens. The results also revealed that the grits waste from cellulose industry could be used as a total replacement of traditional calcareous material in wall tile formulations.

Effect of granitic rock wastes and basalt on microstructure and properties of porcelain stoneware

Porcelain stoneware tiles are materials with excellent technical properties processed by using high temperatures and fast firing cycles that requires high-quality fluxes. However, high cost and exhaustive reserves of traditional used feldspars limits their use. The study of the fluxing potential of granitic rock wastes and basalts and their effect on properties and microstructure of porcelain tiles was carried out. The addition of the basalt in the amount of 7.5 wt% leads to the best densification behavior and near-zero water absorption of the samples. The properties of porcelain tiles with addition of basalt and granitic rock wastes show the possibility of their limit use as fluxes in ceramic tiles industry.

Valorization of Municipal Waterworks Sludge to Produce Ceramic Floor Tiles

In municipal waterworks large amounts of waste in the form of sludge have to be discarded. This investigation focuses on the processing of ceramic floor tiles incorporated with a municipal waterworks sludge. Four floor tile formulations containing up to 10 wt. % of the municipal waterworks sludge were prepared in order to replace the kaolin. The floor tile processing route consisted of dry powder granulation, uniaxial pressing, and firing between 1190 and 1250 °C using a fast-firing cycle (<60 min). The densification behavior and technological properties of the floor tile pieces as function of the sludge addition and firing temperature were determined. The development of the microstructure was followed by XRD and SEM/EDS. The results show that the replacement of kaolin with municipal waterworks sludge, in the range up to 10 wt. %, allows the production of ceramic floor tiles (group BIb and group BIIa, ISO 13006 Standard) at lower firing temperatures. These results suggest a new possibility of valorization of municipal waterworks sludge in order to bring economic and environmental benefits.

Incorporation of Lead Containing TV Tube Glass Waste in Aluminous Porcelain

The aim of this work was to study the incorporation of lead containing TV tube glass waste as a method to provide alternative raw material for aluminous electrical porcelain. For this purpose, aluminous porcelain formulations containing up to 30 wt.% of TV tube glass waste as a replacement for traditional flux material (sodium feldspar) were pressed and fired in air at 1300 oC using a fast-firing cycle (< 60 min). X-ray diffraction (XRD), scanning electron microscopy (SEM), linear shrinkage, apparent density, water absorption, and electrical resistivity have been carried out. The results indicated that the aluminous porcelain pieces containing up to 30 wt.% of TV tube glass waste rich in PbO with water absorption between 0.42 and 0.45% and volume electrical resistivity between 1.91 and 2.93 x 1011 Ω.cm have high potential to work as electrical insulator material. This use of lead containing TV tube glass waste can contribute greatly to reducing the environmental impacts related to it, and also save the sources of non-renewable raw materials used in the electrical porcelain sector.

Crystallisation of nepheline-based glass frits through fast-firing process

The aim of this research was to study the feasibility of producing sintered nepheline glass-ceramic through a fast firing route. The thermal behaviour of the original glass was analyzed by mean of differential scanning calorimetry (DSC) and X-ray diffractometry (XRD). The microstructural analysis of glass-ceramic materials was carried out by field-emission scanning electron microscopy (FE-SEM). The results showed that the studied wastes are able to produce a glass and glass-ceramic materials through a sinter-crystallisation process, 100μm being the critical glass particle size. Glass-ceramics are composed of residual glassy phase and crystalline phases such as nepheline (NaAlSiO4), augite (Ca, Na)(Mg, Fe, Al)(Si, Al)2O4 and a solid solution belonging to the melilite group (Ca, Na)(Al, Mg, Fe,)(Si, Al)2O7. In a first evaluation, water absorption (0.02%) and bending strength (71MPa) of glass-ceramic achieved after thermal treatment at 1100°C/5min suggest that sintered glass-ceramics can be easily produced from coal fly ash and metallurgical slag wastes by a fast-firing cycle and they are extremely serviceable for outdoor flooring and wall cladding.

Elastic properties of porous porcelain stoneware tiles

Porcelain stoneware tiles are industrially processed by using high sintering temperatures and fast firing cycles that result in products characterized by an almost impervious surface layer surrounding a rather porous bulk material. Since mechanical properties are affected by porosity, the knowledge of the material stiffness is an important parameter to define the service behavior of tiles. In the present investigation, porcelain stoneware samples having different closed porosity were investigated in order to understand the influence of the porosity on the elastic constants of the materials.Based on the quantitative XRD phase composition, elastic constants have been calculated via Voigt-Reuss-Hill averaging, and the influence of porosity has been taken into account via power-law and exponential relations. It is shown that the effective elastic constants predicted by exponential and power-law relations are in agreement with experimental values. It may be concluded that for this class of materials, in the porosity range below 14–16%, both exponential and power-law relations are helpful tools to design tiles with controlled microstructure and tailored mechanical properties.

Densification behavior of floor tiles added with sugarcane bagasse ash waste

In this work, the effect of sugarcane bagasse ash waste on the densification behavior of vitrified floor tiles was investigated. Four tile formulations containing up to 5wt. % of sugarcane bagasse ash waste as a replacement of quartz were prepared. The floor tile manufacturing route consisted of the following steps: powder preparation by the dry process, uniaxial pressing, and firing at temperatures between 1190°C and 1250°C using a fast-firing cycle. The densification was measured by three parameters: linear shrinkage, water absorption, and flexural strength. The microstructure was evaluated by XRD and SEM. The experimental results indicated that the densification behavior of floor tile formulations was influenced by both the amount of sugarcane bagasse ash waste and the maximum firing temperature. Microstructural variation occurred during firing. However, the use of sugarcane bagasse ash waste had little effect on phase evolution during the fast-firing cycle. An optimum amount of sugarcane bagasse ash waste (up to 2.5wt. %) for the replacement of quartz allowed for the highest quality production of floor tile materials.

Wood waste incorporation for lightweight porcelain stoneware tiles with tailored thermal conductivity

The increasing demand for building materials exerts tremendous pressure on the Earth's natural resources, as many raw materials are reaching critical and distressing levels. As a result new materials that can, totally or partially, substitute conventional raw materials have been the focus of intense research and are eagerly pursued. Waste materials emerge as ideal candidates for partial substitution of ceramic raw materials, due to their large scale production. Despite their high annual production rate wood wastes have seldom be used in building materials, so their valorisation in the construction sector would be highly advantageous from an environmental and economic point of view. This work reports the incorporation of wood wastes (sawdust) as a pore forming agent into ceramic tiles for the production of lightweight bi-layered ceramic tiles with tailored thermal conductivity. To the best of our knowledge this is the first investigation concerning the incorporation of wood wastes in this type of material. Optical micrographs of the sintered discs did not reveal the presence of a black core, indicating that sawdust was totally burn out even when industrial fast-firing cycles were applied. Moreover its decomposition does not induce defects in the ceramic bodies. The results demonstrate that sawdust incorporation promotes a threefold decrease in the thermal conductivity of the ceramic tile, and reduces product weight (up to 7.5%), while maintaining suitable mechanical resistance in comparison to commercial stoneware tiles. Sawdust can be successfully incorporated into stoneware ceramic tiles ensuring environmental, technical and economic advantages: waste valorisation by sawdust reuse (environmental advantage); density reduction of the product which decreases the tiles transportation and distribution costs (economic advantage); restrain energy loss (technical advantage). The new and exciting features provided by sawdust incorporation may widen the range of applications of this common product while simultaneously contributing towards sustainable construction.

Process and material parameters towards the design of fast firing cycles for high permeability MnZn ferrites

In this article the design of a fast sintering cycle of high permeability (ui>5000) MnZn ferrites is described. This has been accomplished through the optimization of selected parameters in the manufacturing process. The ferrites were prepared following the solid state reaction method and the sintered specimens were electromagnetically evaluated. As found, the combination of the morphology of the raw materials, the incorporation of In2O3 as a dopant, the atmosphere profile, as well as the cooling rates play a major role in the determination of the magnetic performance of the sintered core. The combined optimization of these parameters led to the design of a sintering profile that is 34% faster, while at the same time the initial permeability of the MnZn ferrite is increased by 35% and the magnetic losses are decreased by 14–34%, depending on the frequency level.

Reuse of solid petroleum waste in the manufacture of porcelain stoneware tile

This study investigates the incorporation of solid petroleum waste as raw material into a porcelain stoneware tile body, in replacement to natural kaolin material by up to 5 wt.%. Tile formulations containing solid petroleum waste were pressed and fired at 1240 °C by using a fast-firing cycle. The tile pieces were tested to determine their properties (linear shrinkage, water absorption, apparent density, and flexural strength), sintered microstructure, and leaching toxicity. The results therefore indicated that the growing addition of solid petroleum waste into tile formulations leads to a decrease of linear shrinkage, apparent density, and flexural strength, and to an increase of water absorption of the produced tile materials. It was also found that the replacement of kaolin with solid petroleum waste, in the range up to 2.5 wt.%, allows the production of porcelain stoneware tile (group BIa, ISO 13006 standard). All concentrations of Ag, As, Ba, Cd, Cr (total), Hg, and Pb of the fired porcelain stoneware tile pieces in the leachate comply with the current regulatory limits. These results indicate that the solid petroleum waste could be used for high-quality porcelain stoneware tile production, thus giving rise to a new possibility for an environmentally friendly management of this abundant waste.

Influência da incorporação de resíduo de rocha ornamental sobre as propriedades e microestrutura sinterizada de piso cerâmico

O Brasil é um dos maiores produtores e consumidores de rochas ornamentais no mundo. No entanto, a indústria de rochas ornamentais gera enormes quantidades de resíduos sólidos na forma de pó fino não biodegradável. No século XXI o grande desafio do setor de rochas ornamentais é o descarte final deste abundante resíduo de forma ambientalmente correta. Os resíduos de rochas ornamentais são ricos em materiais fundentes, que promovem a formação de fase líquida e auxiliam na densificação de materiais cerâmicos tradicionais. Neste trabalho foi avaliada a possibilidade de utilização de resíduo de rocha ornamental como um material de fluxo em composição para fabricação de piso cerâmico vitrificado de alta qualidade. As massas cerâmicas contendo até 45 % em peso de resíduo de rocha ornamental foram preparadas pelo processo via seca. Peças cerâmicas prismáticas foram preparadas por prensagem uniaxial a 50 MPa e sinterizadas a 1230 ºC usando um ciclo de queima rápida. As seguintes propriedades física e mecânica foram determinadas: retração linear, absorção de água, massa específica aparente, porosidade aparente e tensão de ruptura a flexão. A microestrutura sinterizada foi acompanhada por microscopia eletrônica de varredura e as fases cristalinas foram identificadas por difração de raios-X. Os resultados mostram que o efeito da adição do resíduo de rocha ornamental foi o de promover maior densificação e propriedades melhoradas dos pisos cerâmicos vitrificados.

Processing of red ceramic using a fast-firing cycle

This work reports on the processing of red ceramic for civil construction using fast-firing cycles. The firing cycle is an important variable in the processing of red ceramic materials, which contributes to a high consumption of energy. The red ceramic pieces were prepared by industrial extrusion and fired at firing temperatures varying from 700 ºC to 1100 ºC using different firing cycles (slow-firing cycle - 1º C/min and fast-firing cycle - 10 ºC/min and 20 °C/min). The technological properties (linear shrinkage, water absorption, apparent porosity, apparent density, and flexural strength) as function of the firing temperature and firing cycle are investigated. The development of the microstructure was followed by SEM/SEI. The results showed that fast-firing red ceramics exhibits technological properties and microstructure comparable to conventionally fired red ceramics, resulting in great advantages in energy saving.

Obtainment of porcelain floor tiles added with petroleum oily sludge

This study focuses on the processing of vitrified floor tiles incorporated with a petroleum oily sludge. Floor tile formulations containing up to 5wt% of the petroleum oily sludge in replacement of kaolin were prepared. The tile formulations were granulated by the dry process, pressed, and fired at temperatures between 1200 and 1250°C using a fast-firing cycle. The specimens were characterized before and after firing. XRD was used to identify the crystalline phases present during sintering and SEM was used to show how the structure changes during densification. Three parameters were used to describe densification: linear shrinkage, water absorption, and flexural strength. The results showed that the petroleum oily sludge could be used as an alternative raw material in the floor tile formulations. The densification behavior of the floor tile pieces is influenced by the petroleum oily sludge addition and firing temperature. The vitrified floor tiles produced reached the technical characteristics of porcelain floor tiles, depending on petroleum oily sludge content and firing temperature.