Metro Tunnel paves the way for sustainable infrastructure with Australia-first trial

The Metro Tunnel Project is taking sustainability in the construction industry to the next level, with an Australia-first low-carbon concrete research project. 

The project has partnered with the University of Melbourne for the innovative research, trialling the use of crushed recycled glass as a replacement for sand in structural concrete mix. 

Using crushed recycled glass, or ‘glass sand’, lowers the environmental impacts of concrete production, by reducing reliance on virgin sand – a raw material that is mostly mined or taken from rivers - and diverting waste glass from landfill.

For the trial, glass sand was used to replace 25 per cent of the virgin sand used in the concrete mix for building suspended work platforms at State Library Station’s La Trobe Street construction site. 

Metro Tunnel Project sustainability lead, Mick Lo Monaco, said the initiative was potentially a first for Australia, if not the world. 

“It’s the first time, as far as we’re aware, that [glass sand concrete mix] has been used in a higher strength building application,” Mr Lo Monaco said. 

Concrete mixes using glass sand in Australia have previously been limited to low-strength applications such as footpaths, he added. 

Mr Lo Monaco said while the trial glass sand concrete mix was being used for temporary structures on the project, the next opportunity is to trial the mix in permanent minor structural elements for streetscaping around the new Metro Tunnel stations. 

“We need to move to low carbon concrete - that’s key to reaching net zero emissions. This is one way to remove [raw materials] from our concrete and use a waste product that would otherwise need to go to landfill.”

Mr Lo Monaco said the initiative also had the potential to create a market for waste glass in Victoria. 

“Victoria has a surplus of waste glass that is traditionally exported overseas because we don’t have a reliable market for it locally. [This initiative] is basically opening up a huge market for that glass,” he said. 

Based on the trial’s success, future trials are now being considered with the potential to increase the glass sand component from 25 per cent to up to 80 per cent.

Meanwhile, the team is making great progress on construction of the Metro Tunnel’s stations and tunnels to get them ready to start testing trains underground in the second half of this year. •