Energy-efficient “glass” bricks as strong as clay

Double-glazed windows are often seen as a useful, if expensive, measure to insulate Australian homes and shave quarterly power bills, now materials scientists are hopeful they’ve cracked a way to introduce similar properties to bricks.

The researchers in Melbourne engineered clay bricks containing 15% reclaimed glass dust, which would have otherwise been unrecyclable, as part of the brick-firing process.

Laboratory testing by the team from RMIT University found the compressive strength of these bricks was similar and possibly slightly better than clay control bricks.

Other compositions of waste glass were trialled as part of the experiment, which saw 100 experimental bricks fired at around 1000°C, but the substitution of 15% of clay for glass by weight was found to be superior. Their results are published in the journal Case Studies in Construction Materials.

The glass waste composite bricks haver better structural strength and insulation properties..

“It requires about 20% less energy compared to manufacturing the standard brick,” says Associate Professor Dilan Robert, who led the research team.

“When it comes to building the house, the benefit comes to the occupants because of the improved thermal characteristics of these bricks – there could be about a 5% saving on energy bills.”

The glass ‘fines’ were obtained in partnership with large-scale Australian recycling company Visy. From there, the clay soils were dried, crushed and sieved, and then mixed with the fines and a proportion of fly ash, which is also used in cement making. It was then compacted, fired and dried into a final specimen.

The applications for its use in masonry are also significant. Robert and his team claim their product can be further altered to introduce colour changes.  Robert also says the RMIT researchers can make the brick 20-30% lighter.

“That can help during transportation with the energy that’s required for transporting the bricks,” he says.

On top of this, he envisages an opportunity to reduce demand for conventional brick building materials, while repurposing unusable wastes for construction materials.

Robert’s team is working with partners to trial their composition in their manufacturing plants. They’re also focussing their research on ways to further improve their brick’s sustainability profile, including the use of enzymes and combusted ash to stabilise the composite clay, which could reduce the temperatures required – and energy needed – to operate brick-making kilns.

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