The Metro Tunnel Project is working with researchers at the University of Melbourne and industry partners to trial the use of recycled crushed glass in structural concrete at the new State Library Station.
Through this trial, it has been demonstrated that 25 per cent of virgin sand used in concrete mix can be replaced with recycled crushed glass, reducing reliance on virgin sand and diverting waste glass from landfill.
This is the first time a recycled glass concrete mix has been used in a structural application on a major infrastructure project anywhere in the world, having previously been limited to footpaths and local roads.
The project trialled the crushed glass concrete mix in the construction of temporary suspended concrete slabs, successfully producing a concrete mix of equal strength and quality.
It is now considering future trials at the University of Melbourne – with the potential to increase virgin sand replacement from 25 to 80 per cent crushed glass.
While high quality glass and larger pieces of broken glass are processed into new glass products, tiny pieces of contaminated broken glass, called fines, have previously had few end-uses and have been stockpiled or sent to landfill.
At the same time, the concrete industry has been facing a shortage of virgin sand. Recycled glass fines (RGF) can be considered as a partial replacement to sand, due to the similarities between their physical and chemical properties.
The University has successfully demonstrated that unwashed RGF of up to 10 per cent by mass can be used as a sand replacement in concrete, fulfilling theAustralian Standards fine aggregate requirement.
The light particles and organic contaminants proved to not cause any issues when this amount of glass is used, accelerating the potential uptake of RGF into the infrastructure and construction industries.
In addition to creating a new use for glass fines, the Department of Transport is likely to see a reduction in the costs of these construction products, as the unwashed glass will require less processing and may be preferred over more expensive and scarce virgin materials.