Guia Guarini
National Research Council
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Ceramics International | 2002
F. Matteucci; Michele Dondi; Guia Guarini
The feasibility of waste glass recycling in ceramic tile production was assessed with special reference to fully vitrified products (porcelain stoneware). Soda-lime float or container glass was introduced, in replacement of sodic feldspar, in typical porcelain stoneware bodies (up to 10 wt.%) that underwent a laboratory simulation of tilemaking process, with a technological and compositional characterization of both fired and unfired tiles. Soda-lime glass had no significant effect on semi-finished products, but it influenced remarkably the firing behaviour, increasing shrinkage and closed porosity, decreasing open porosity and bulk density, and lowering mechanical and tribological performances. Waste glass promotes a more effective melting of quartz and a partial dissolution of mullite, leading to a more abundant and less viscous liquid phase, which accelerates the sintering kinetics. In conclusion, soda-lime glass can be used in small amounts (5% or less) with tolerable modifications of technological behaviour and performances of porcelain stoneware tiles.
Waste Management | 2009
Michele Dondi; Guia Guarini; M. Raimondo; Chiara Zanelli
Disposal of PC monitors and TV sets is a growing problem, with over 40% of the weight of these systems comprised of waste glasses with high Pb (funnel) or Ba-Sr concentrations (panel), making them unsuitable for recycling and manufacturing new glass. A possible way to re-use these glasses is in the manufacturing of clay bricks and roof tiles. This possibility was appraised by laboratory simulation of the brickmaking process and technological characterization of unfired and fired products. The recycling of both funnel and panel glasses into clay bodies is technologically feasible, resulting in a substantially reduced plasticity behaviour during shaping-drying (implying a reduction of mechanical strength), and a promotion of sintering during firing. No significant release of Pb, Ba, and Sr was observed during the firing and leaching test for the carbonate-poor body; in contrast, some Pb volatilization during firing and Sr leaching were observed for the carbonate-rich body. Additions of 2 wt.% appear to be practicable, while 5 wt.% glass induces unacceptable modifications of technological properties. The recommended amount is within 2 and 4 wt.%, depending on the characteristics of the clay bodies. The main constraint is that the glass must have a particle size below the limit of the pan mills used in brickmaking (<1mm).
Journal of The European Ceramic Society | 2003
Roberto de Gennaro; Piergiulio Cappelletti; Guido Cerri; Maurizio de Gennaro; Michele Dondi; Guia Guarini; Alessio Langella; Debora Naimo
Low-cost zeolitic rocks are promising substitutes for feldspathic fluxes in ceramic bodies, since their fusibility, modest hardness and high cation exchange capacity (CEC) should improve grinding and sintering. Five large-scale Italian deposits of natural zeolites with different mineralogy were characterised and tested in porcelain stoneware bodies. Their behaviour during processing was appraised and compared with that of zeolite-free bodies. Zeolites increased the slip viscosity during wet grinding, causing a coarser grain size distribution and consequently some drawbacks in both unfired and fired tiles. After overcoming this hindrance by dry grinding of zeolite rocks, the technological behaviour of zeolite-bearing tiles appear to be similar to that of current porcelain stoneware, though with larger firing shrinkage and residual closed porosity.
Journal of Environmental Management | 2011
R. Alonso-Santurde; A. Andrés; Javier R. Viguri; M. Raimondo; Guia Guarini; Chiara Zanelli; Michele Dondi
The feasibility of recycling spent foundry sand in clay bricks was assessed in laboratory, pilot line and industrial trials, using naturally occurring sand as a reference. Raw materials were analyzed by X-ray fluorescence, X-ray diffraction, particle size distribution, and leaching and combined to produce bodies containing up to 35% wt. sand. The extrusion, drying and firing behaviour (plasticity, drying sensitivity, mechanical strength, bulk density, water absorption, and shrinkage) were determined. The microstructure, phase composition, durability and leaching (EN 12457, granular materials, end-life step, European Waste Landfill Directive; NEN 7345, monolithic materials, use-life step, Dutch Building Material Decree) were evaluated for bricks manufactured at optimal firing temperature. These results demonstrate that spent foundry sand can be recycled in clay bricks. There are no relevant technological drawbacks, but the feasibility strongly depends on the properties of the raw materials. Spent foundry sand may be introduced into bricks up to 30% wt. Most of the hazardous elements from the spent foundry sand are inertized during firing and the concentrations of hazardous components in the leachates are below the standard threshold for inert waste category landfill excepting for chromium and lead; however, their environmental risk during their use-life step can be considered negligible.
Journal of The European Ceramic Society | 2002
Michele Dondi; Guia Guarini; M. Raimondo; I. Venturi
Abstract In order to appraise the technological feasibility of the Orimulsion ash recycling in clay bricks, a laboratory simulation of the brickmaking process was carried out with various clay/ash mixtures up to 6% waste. Two different clays were selected and mixes were characterized by XRF, XRPD, TGA–DTA, TDA and PSD analyses. Plasticity, extrusion and drying behaviour, and mechanical strength, were determined on unfired mixtures, while shrinkage, water absorption, bulk density, modulus of rupture, pore size distribution, microstructure and phase composition were measured on fired bricks. Orimulsion ash caused some detrimental changes of technological properties of both unfired and fired products, concerning particularly plasticity, drying rate and drying sensitivity, porosity and colour. These effects were slightly different on the two raw materials, the carbonate-rich clay being less sensitive to the presence of ash with respect to the carbonate-free clay. In all events, drawbacks appeared to be tolerable, in technological terms, for low waste additions, approximately 1–2% ash.
Journal of The European Ceramic Society | 2002
Michele Dondi; G. Ercolani; Guia Guarini; M. Raimondo
Abstract A bitumen-in-water emulsion (Orimulsion) is currently used as a fuel in several thermal power plants worldwide. Orimulsion combustion produces a fly ash rich in S, Mg, V and Ni, which is processed to recover metals. In order to assess the feasibility of a recycling in clay brick production, a characterization of the physico-chemical and thermal properties of ash was performed by ICP–OES, XRPD, SEM, BET and TGA–DTA techniques. Orimulsion ash resulted in fine-grained (aggregates of submicronic particles), highly hygroscopic, constituted mainly of magnesium sulphate, vanadyl sulphates and magnesium and nickel oxides, and thermally unstable in the usual brick firing conditions. These features can affect the brickmaking process, particularly the plasticity of the clay body and its drying and firing behaviour; furthermore, a mobilization of sulphates could occur, promoting the formation of efflorescence and/or the SOx release during firing.
Applied Clay Science | 2001
Michele Dondi; Guia Guarini; Paola Ligas; M. Palomba; M. Raimondo
Abstract Kaolinitic materials crop out in the Tresnuraghes mining district (Western Sardinia, Italy). Three main kaolinitic deposits, located in the Patalza, Salamura and Su Fongarazzu areas, respectively, were investigated in order to assess their potential in the ceramic industry. The parent rock-types of this raw material are the Oligocene–Miocene rhyolitic–rhyodacitic ignimbrites. Chemical and mineralogical analyses were performed on representative samples of each deposit, by XRD and XRF methodologies. The chemical analyses generally show high silica and low alumina contents in all samples, typical of weakly kaolinized materials. The main mineralogical association consists of kaolinite and cristobalite with quartz and smectite as the minor components. Alunite may be present as a main mineral in the Salamura and Su Fongarazzu deposits, making these clay materials unsuitable for ceramic applications. The Patalza deposit exhibits low iron and sulphur contents, but low plasticity and excessive refractoriness. The Patalza materials can be used as unconventional raw materials to replace both kaolin and silica in white-firing bodies. Results show that the introduction of the Patalza “kaolins” was well tolerated in bodies for tableware, wall and floor tiles, without significant changes in porosity, bulk density, pore size distribution and coefficient of thermal expansion. The main drawback of using the Patalza material is the slight increase of firing shrinkage, while the main advantage is a systematic increase in mechanical resistance.
Key Engineering Materials | 2004
Chiara Zanelli; Michele Dondi; Guia Guarini; M. Raimondo; I. Roncarati
A typical industrial formulation for porcelain stoneware tiles was modified by adding synthetic mullite, and mullite-precursors, such as kaolin and gibbsite in order to enhance the mechanical properties by increasing the mullite content. The change in the physical properties as well as the technological and mechanical behaviour were evaluated on the basis of the phase composition modifications. Introduction Porcelain stoneware tiles are primarily composed of clays, feldspars and quartz, heat-treated to form a mixture of glass and crystalline phases (new formed and residual ones), which are characterized by high mechanical, chemical and tribological properties, besides excellent aesthetic appearance. The current trend of producing ceramic tiles having larger and larger formats, for ever more severe applications, require to further enhance their mechanical behaviour, in terms of both flexural strength and fracture toughness. Many theories were proposed to explain the strength of porcelain ware, mainly based on the body mullite content [1,2], the existence of compressive or tensile stresses, caused by the thermal expansion coefficient differences [3], or the presence of dispersed strengthening particles [4,5]. However, only few papers in the literature deal with the effectiveness of these hyphotesis for porcelain stoneware bodies, leaving many opportunities to better understand the role of the microstructure and phase composition on the mechanical strength, fracture mechanisms and crack propagation [6, 7]. The microstructure of porcelain stoneware bodies, in terms of nature and amount of crystalline phases, can be achieved as a result of in-situ chemical transformations or by adding unreactive components as substitutes of the basic raw materials. This paper is focused on the possibility of improving the mechanical performances of porcelain stoneware tiles, through the addition to the starting powders of synthetic mullite and mullite-precursors (kaolin and gibbsite), in order to evaluate their strengthening and toughening role. For this purpose, the microstructural evolution, in terms of physical properties, as well as the mechanical strength and the fracture behaviour of the products were evaluated. Materials and Methods A typical industrial porcelain stoneware body (B) was modified adding mullite (M), kaolin (K) and gibbsite (G) in partial replacement of quartz. The addition amounts were 3-6-12 % for mullite and gibbsite, 5-10-20% for kaolin (Table 1). The production process was simulated at a laboratory scale by wet grinding, pelletization and humidification with 5-6 % water. Tiles (110 x 55 x 5 mm 3 ) were pressed at 40 MPa, dried at 105±5°C and fired in a roller kiln, with an industrial thermal-like cycle of 51 minutes, from cold to cold, at a maximum temperature of 1220°C. Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 1491-1494 doi:10.4028/www.scientific.net/KEM.264-268.1491
Key Engineering Materials | 2004
Michele Dondi; Guia Guarini; M. Raimondo; E.R. Almendra; P.M.T. Cavalcante
This work deals with the appraisal of the most important microstructural parameters influencing the stain resistance of polished porcelain stoneware tiles. The correlations between the stain resistance on one side and bulk or surface characteristics on the other side were evaluated through a statistical approach, which provided a previsional model of the staining behaviour of tiles, based on the surface roughness as well as the pore amount, size and morphology.
WIT Transactions on Ecology and the Environment | 2002
Francesca Mazzanti; L Cunico; G Dircetti; Michele Dondi; Guia Guarini
The feasibility of steel slag recycling in bricks was assessed through laboratory trials on three different topologies of wastes and clay bodies. The use of slag, previously ground below 3 mm, is substantially possible for additions of 2-3% without particular hindrances of technological nature. Additions of up to 5-670 seem to be practicable, even though with a porosity increase and a deterioration of the mechanical properties of both unfired and fired products. Larger amounts of slag are decidedly inadvisable for the changes in the chemical and physical characteristics of products.