Use of scrap soda-lime-silica glass in traditional ceramics

摘要

Alternatives ways of recycling soda-lime-silica scrap glass (SLS) glass, apart from remelting can offer certain advantages and may be implemented when glass production is not suitable. For the ceramics industry, the incorporation of glass into the ceramic body may improve the quality of fired products and save energy. Mixtures of SLS glass and ceramic raw materials used for the production of porcelain stoneware tiles and heavy-clay products were developed and examined. In the case of porcelain stoneware tiles, several modified mixes were prepared by replacing different amounts of the fluxing component, sodium feldspathic sand. For roofing tiles, SLS glass was added at a fixed percentage in the body mixes. The fired samples were characterised in terms of linear shrinkage, water absorption, flexural strength and reliability. Micro-structure and the main phase transformations in the fired samples were examined by x-ray diffraction and by scanning electron microscopy along with EDS microanalysis. The results, for the porcelain stoneware body mix, show that a substitution of the fluxing component in the range of 5-10 wt percent is feasible. The new formulations had lower water absorptions, adequate flexural strengths and a consistent increase in reliability due to improved homogeneity. For substitutions exceeding 10 wt percent, plagioclase was crystallised, which inhibited the formation of mullite and did not favour densification. The results regarding the modified body mix for heavy clay products have shown that a glass additions up to 30 wt percent are feasible. New crystalline phases were developed within and at the interface of the glass grains. The particle size distribution of the glass and the firing temperature both influenced the physical and mechanical characteristics whereas they had a minor effect on the mineralogy. The fired products demonstrated improved characteristics in terms of water absorption and bending strength.