- Material sciences and production
TILES FROM WASTE MATERIALS
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.
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 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.
Mirja Niemelä, @
University of Art and Design Helsinki UIAH
Department of Ceramics and Glass
Hämeentie 135 C
FIN-00560 Helsinki, Finland
fax: +358 9 75630275