Increasing glass content in bricks

Clay Technology magazine
16 Oct 2008

A brick containing 97% recycled glass has improved energy efficiency compared to clay bricks, claims UK firm Geofusion, based in Worcester.

The geobrick is produced from a combination of container glass and cathode ray tube panel glass. The materials are ground to particle sizes of less than two millimetres and blended with a non-organic binder and coloured pigments (the company was not able to reveal the exact composition of the additives).

The brick is then placed in moulds and fired at around 650ºC for seven hours, during which time the glass fuses together. ‘The energy used for the process is less intensive than firing clay,’ says Mike Everard, Director and Joint Founder of Geofusion. Clay bricks usually need to be heated to over 1,000ºC for up to three days. The geobrick also offers thermal efficiencies similar to clay products, he adds.

The building material was first developed by Professor Mike Anderson of Staffordshire University over a five-year period. ‘He designed it to meet all [British Standards BS EN] and be used in almost any masonry project,’ says Everard.

Another reported environmental benefit is that it diverts material that usually ends up in landfill, such as coloured glass and television screens. The company has received funding from the UK Waste & Resources Action Programme to make use of these materials, and has deals with several major recycling firms to receive the tonnages of glass required.

A technical expert from a major UK brick manufacturer (who wishes to remain anonymous) notes that ‘there are good and bad environmental points’ for both clay and glass bricks. In recent years, clay brick companies have endeavoured to increase their use of materials from alternative, recycled and secondary sources, and, like the glass brick, their products are fully recyclable, he says.

'The problem with glass is the energy it takes to grind it down to the correct size, which can be intensive,’ he adds. ‘You have to compare the products across the full lifecycle.’

He also believes the material’s appearance could not compete with clay in terms of natural colour and texture.

However, the glass brick is not intended to replace clay bricks, says Everard. ‘It is not meant to be an everyday product, but is for a specialised market that is looking for a green brick with a specific colour and texture.’

It is claimed that the geobrick can also be ‘engineered’ to be as porous as required, allowing rainwater to be collected and distributed for reuse. It is even said to be able to harvest water that falls onto vertical walls.

Geofusion had originally hoped to build a production plant by 2009, but has had to postpone plans due to the financial difficulties that have beset the UK housing industry. The company is seeking a finanical partner to help begin manufacture.

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