(May 2010) „We’re not out of the woods yet“ writes Dr. José Carlos da Rocha referring to a method to turn slurry from quarries into glass. The basic research was done by Michelle Pereira Babiski in her doctoral thesis in the Brazilian Instituto Nacianal de Technologia (INT). Her mentor was chemist Carlos da Rocha. Also participating in the process of research were Dr. Luís Henrique Leme Louro (Ph.D.) and Dr. Marcelo Prado (D.Sc.) of the Instituto Militar de Engenharia (IME).
Michelle Pereira Babisk could prove that silicate rock is a suitable raw material for production of coloured glass as used in the production of green bottles.
The seminal idea was to make a virtue out of necessity. The quarry saw dust contains a great amount of iron, which is added during the sawing process because of its desirable abrasive properties. However, this was precisely the reason why the use of quarry refuse for building purposes was limited.
„So it only seemed natural to reflect on coloured glass where iron could serve as pigmentation“, writes Carlos da Rocha.
One of the main challenges in the process is to achieve a homogenous grain but also the correct composition of the slurry and additives. As Carlos da Rocha stressed there are no significant differences to glass produced from traditional ingredients.
Analysing profitability requires further attention.
José Carlos da Rocha (Mail)
Research in the European Union
The European Union has recently embraced two new projects involving stone refuse. One is called Eco-Stone, claiming: „The project will implement a sustainable system for the production and use of natural stone… The project is focused on optimising the use of natural resources and raw materials; optimising energy consumption in the production chain; and encouraging architects to using multifunctional natural stone-based materials that are more energy-efficient and environmentally friendly.“
Participating institutes (Spanish)
The EcoBrick-project revolves around making bricks from sewage slurry. So far no reflections have been made on the use of quarry slurry according to Professor Dr. Karl-Ulrich Rudolph of the University of Witten-Herdecke, who sees its use as distinct possibility.
Congresses in India and Spain
The disposal and use of refuse from stone production was a central theme of the Global Stone Congress held from March 2nd to 5th in the Spanish city of Alicante. Among others Dr. Nicola Careddu (Ph.D.) presented the work of her research group at the Italian University in Cagliari. He determined that marble sawdust could be used as to upgrade raw material in the brick production. The material is made up of nearly 100% carbonate and has a very fine grain. Thus it is possible to reduce the addition of clay. First trials using slurry from the region of Orosei in Sardinia were encouraging. (pdf)
Other research in Careddu’s scope deals with mining and surface treatment using water jets.
Nicola Careddu (Mail)
Refuse disposal was also an important theme at the Global Stone Technology Forum held at the beginning of the year in the Indian City of Jaipur. The talks can be downloaded. A Web-page offers talks from the 2007 Forum.
Speaking of refuse: we perused the statistical yearbook „Stone 2009“ compiled by Carlo Montani. The 1,942,500 m² slabs (2 cm thick) produced 2008 world-wide left behind 796,400 m² of refuse or 41% of the original production. Interestingly, the average percentage of waste is the same in all countries. Also interesting is that the percentage of refuse was reduced from 69% in 2003 to 41% by latest statistics. („Stone 2009“, Carlo Montani, Edizioni Il Sole 24 Ore Business Media, 32 €, ISBN 978-88-8138-124-1 – Code N. 10330).