Metro Tunnel trials recycled glass in concrete

The trial has demonstrated that 25% 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.

The crushed glass concrete mix was used in the construction of temporary suspended concrete slabs, producing a concrete mix of equal strength and quality to traditional concrete.

It is the first time a recycled glass concrete mix has been used in a structural application on a major infrastructure project. It has previously been limited to footpaths and local roads.

Cross Yarra Partnership, which is completing the tunnels and stations contract, says it is considering further trials at the University of Melbourne – with the potential to increase virgin sand replacement from 25% to 80% crushed glass. The consortium comprises Lendlease Engineering, John Holland Bouygues Construction and Capella Capital.

CYP sustainability lead Mick Lo Monaco said the consortium hoped that by providing a field trial site for the research it could pave the way for full-scale commercialisation of recycled glass in structural concrete.

The research is part of the project’s sustainability commitment. According to a video on the project website, by using recycled industrial by-products instead of cement, the project has reduced its cement use by more than 50%.

The Metro Tunnel is the first step towards a metro-style rail network for Melbourne. It includes twin 9km tunnels from the west of the city to the south-east and five underground stations. The four TBMs completed tunnelling in May 2021.