Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Development and demonstration of tiles process

Development and demonstration of tiles process consists in:
- Nucleation and crystallisation of original glass;
- Processing of tiles;
- Coloration of tiles.

Nucleation and crystallisation of original glass:
As is nowadays useful for the production of glass-ceramics, the determination of nucleation rate of crystals at different temperatures (700- 750ºC) and several heating rates from the vitreous slag coming from the arc- plasma processing of wastes has been carried out by DTA analysis. This has given convex curves from where determination of maximum nucleation is possible. To ascertain the predominant crystallization mechanism for such type of “original glass” from plasma, the DTA experiments were made in bulk monolite and fine powdered samples (< 35µm), calculating the activation energy for crystallization. Static (quenched) TTT curves have been also determined from the pressed powder of original glass due to the dominant surface crystallization mechanism here discovered for this type of glass. After thermal treatments in the 800-1000ºC range, the crystalline phases have been identified in the final products, viz: Gehlenite, akermanite and wollastonite, being at higher temperatures only the wollastonite (CaSiO3) the dominant phase.

Microstructure analysis carried out by SEM/ EDX show compacted crystallization of wollastonite fibres embedded in the residual glassy matrix. The information given by this result is of high relevance for the definition of the processing of glasses coming from plasma and possible recycling into the production of “wastiles”.

Processing of tiles:
After crushing and sieving of the vitreous slag coming from the arc-plasma processing, axial pressing operations have been carried out followed by thermal cycling. Several small prototypes of “wastiles” (50x 0x5mm) have been obtained in the laboratory scale from different wastes. Optimisation of compositional design is a very critical step for overcoming the composition heterogeneities of original glasses. Optimum tiles depict a full sintered and vitrified texture with brown colour and glassy brilliant surface. A wide range of aspects was obtained between 800- 1000ºC and very short times of heating. Physical, mechanical and leaching analysis gives values in the range (or improved) of conventional commercial tiles. After testing of processing of tiles in the laboratory scale heating in electric furnaces at normal atmosphere, the processing was repeated on industrial scale roller furnace (reducing atmosphere) with the obtaining of 120x150x7mm tiles brown colour. The mechanical properties were in the range of: Microhardnes: 5.0-5. 6GPa; Modulus of Elasticity = 90 -138GPa and toughness = 1.0 -2.0 Mpam1/2. The flexural strength for this type of tiles are in the range of s F: 70- 80MPa.

Coloration of tiles:
In order to wide the commercial capabilities of wastiles as construction materials for coverings or pavements of buildings and/or even civil engineering applications, have been obtained several shapes and colours of wastiles from the plasma processing by using commercial ceramic pigments applied to the same processing.

That is:
a) Bulk coloured wastiles;
b) Surface coloured glazed tiles and
c) Mosaic coloured glass-ceramics.

In the case of a) tiles, colours with graduated tonalities were obtained: green, brown and dark-yellow. Large size coloured tiles of 120x150x7mm were obtained at industrial scale roller furnace. From the b) tiles glazed: blue, green, brown, pearl, grey and purple, even developing a specific glass- ceramic glaze for this application. From c) tiles (shaped in small triangles of 30x30x30mm and thickness of 3mm) colours: granate, orange, dark-yellow, green, dark-blue and violet. A proposal of design has been presented as several combinations of these tiles for external/internal wall coverings producing a wide range of decoration possibilities which should be developed more specific applications in construction via a demonstration project running after this project. Leaching properties have been determined accomplishing these products the EPA standards.

Informazioni correlate

Reported by

Instituto de Ciencias de la Construcción Eduardo Torroja, CSIC
C/ Serrano Galvache s/n
28033 Madrid
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