Building waste turned into bricks 

'Green' bricks could be the thing of the future for the Danish building sector. They are produced from crushed tiles and old mortar and thus make no inroads into natural resources of sand, clay and gravel. They save on energy because they harden at room temperature, with reduced levels of CO2 discharges. A third advantage is that they allow building waste to be recycled instead of adding to the already large piles of waste.

'Green' bricks are now to be used for the very first time in a major building project. COWI is leading the project, which, with the financial support of the 'Programme for the promotion of organic building', will monitor and assess the construction of 26 organic family council houses in Herning. The housing company Herning Boligselskab is economically responsible for the project, in which a representative cross-section of the association's partners are taking part.

Close scrutiny

The overriding aim of the project is to promote sustainable development in the Danish building sector. "We expect the project to give us experience that can increase the use of green bricks in the building industry," says COWI Project Manager Niels Møller Jensen.

COWI will scrutinise the project from the planning stages, through construction and for a year after the houses are handed over to the owner, scheduled for May 2003. The assessment will include the impact affect of green bricks on the building process, what mortar gives the best working conditions, how to avoid crack formation and how the bricks age. COWI is also drawing up a life cycle analysis that evaluates the expected lifetime of the bricks, the working environment during construction, the environmental impact, consumption of resources, chemicals, indoor climate and health factors in the life of the building.

The project was developed together with the Municipality of Herning and contains a number of traditional organic elements such as using rainwater for flushing toilets, solar heating and alternative insulation materials.

Recycling

95 per cent of the composition of green bricks is crushed tiles, and there are enough of them about, as about half the demolition material in Denmark is tiles. Today, most of them are used as ballast in road building. But waste treatment equipment and moulding machines allow the tiles to be recycled as bricks. The crushed tile and mortar granules are bound together and moulded under high pressure and vibration to form the bricks. 15 green bricks can be produced for the same energy as one brick made in a kiln.

Published 28.05.2002