The project aimed at developing a method
for utilizing waste glass by sintering and pressing fine ground glass.
The main part of the project (19941995) was financed by the Technology
Development Center of Finland TEKES and it was carried out in cooperation
with YTV, Helsinki Metropolitan Area Council, Tampere University of Technology
and Suomen Erikoismurskaus Oy, Siilinjärvi. Two researchers, Päivi
Kekäläinen (UIAH) and Markku Rajala (UIAH), were working on this
project from March 1994 until the end of 1997 in several periods.
The results indicate that sintered glass is a noteworthy
material for facing tiles or other clinker applications. However, the results
the project produced are preliminary and are not yet sufficient for building
up actual production.
In the sintering and pressing process, first the
glass is ground to a fine powder (particle size under 0,5 mm) and mixed
with a binder. The mixture is portioned out into a metal die and pressed
(300500 kg/cm2). The pressed article is removed from the die and fired
in a kiln to the sintering temperature, 700900°C. The result is
hard, somewhat porous glass. It is not transparent or does not otherwise
look similar to molten glass.
The conventional policy to utilize waste glass
is to melt the glass and manufacture packages, glass fibre, etc. Using
the sintering process it is possible to achieve several advantages over
melting glass. Sintering takes place at 700900°C, whereas melting
the glass requires about 1400°C. This means considerable savings on
energy costs. Due to the lower temperature, the expenses of the kiln materials
are also lower. Recycled glass often contains some impurities, metal etc.
This is a problem when processing molten glass. A sintered glass structure
will bear impurities both technically and aesthetically.