During 1994 I did research in the use of waste materials in ceramic production. The materials I used are sewage sludge from a water treatment plant, fly ash from a coal fired power plant, recycled glass and deinking waste from the paper industry. Of those materials my main interest was in sewage sludge and fly ash. 

Dn 1995 I am studying the manufacturing and designing of a ceramic tile of waste materials and clay, either an exterior or an interior tile. In using waste materials in the body I use the properties the waste has. For example, sewage sludge contains iron oxide, which causes a greyish colour in the white ceramic body at high temperature, and paper waste (deinking waste) has fibres which give the tile green strength. The analysis of the waste materials comes close to some ceramic raw material analysis and therefore they are suitable materials for ceramic use. 

Materials

Dhe tile is mainly made from sewage sludge, fly ash, deinking waste, recycled glass and clay (red- or whitefired clay). The waste part of the ceramic body has to be as high as possible (over 80%), which gives the tile an ecological aspect. The sewage sludge originates from the purification process of wastewater at water treatment plants. In tiles I use calcinated sludge, which is easier to use than pure sludge. Fly ash originates from cleaning the fuel gases in power plants. Fly ash is a valuable ceramic raw material because it has already been fired once, which makes it a good filler for a ceramic body. 

Recycled glass is mainly used in the production of glass wool. The crushed glass can be used as a melting or colouring agent in a ceramic body. Glass lowers the burning temperature in firing. The Deinking of recycled paper produces waste that needs to be disposed of. Deinking reject is mainly china clay and paper fibres. 

Deinking waste is a good binder, because it contains paper fibres which give green strength to the tile body and make the tile lighter. The kaolin gives white colour to the body. The clays used in these bodies were ball clay and red earthenware. 

Design

Design of the waste product is important. It gives quality and aesthetics to the waste product and it stimulates people to use waste products. 

 

Dn the planning of the tile I have taken into consideration the properties of the waste materials and the design of the tile. With the paperwaste in the claybody it is possible to make a large, thin and light tile. The big size of the tile means that it is easy to design large, impressive surfaces. Using simple elements, such as a relief like surface or coloured glaze, it is possible to create, large impressive surfaces. 

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Mirja Niemelä, @
Research Scientist

University of Art and Design Helsinki UIAH
Department of Ceramics and Glass
Hämeentie 135 C 
FIN-00560 Helsinki, Finland 
fax: +358 9 75630275