With modern cities around the world striving to be more sustainable, mass rapid transport systems are essential – enabling large numbers of people to move around while generating fewer emissions.
Melbourne, Australia's second largest city, is no exception, and its stunning Metro Tunnel, which opened at the end of 2025, has created capacity for 500 000 more passengers every week during peak periods.
An icon of sustainable infrastructure, the Metro Tunnel was built to last with Holcim solutions inside.
150 000 tons of CO2 emissions saved
Contributed to 52% reduction in Portland cement across tunnels and stations
World first use of structural-grade concrete with recycled glass in an infrastructure project
THE VISION
Melbourne is booming, with 6 million people expected to call it home by 2030. The city needed to create more ways for them to move around Melbourne, and The Metro Tunnel was commissioned as the largest transformation of the city’s electric rail network in decades, adding five new stations to connect the city’s northwest and southeast suburbs.
Cross Yarra Partnership (CYP), the consortium responsible for building this generational project, prized sustainability throughout its planning, design, construction and future running phases, as well as lasting economic, environmental and social benefits.
THE SOLUTION
CYP knew an infrastructure project of this size would require a massive amount of energy and materials – above all, concrete and cement. It tasked Holcim with providing concrete that minimized raw material use wherever possible, without compromising strength or performance.
Working closely with CYP, Holcim supplied more than 600 000m3 of low-carbon concrete, including 45 specialized mixes for a variety of applications. This helped to reduce the project’s cement use by 52% – exceeding the customer’s initial target of 44%, and cut 150 000 tons of CO2 emissions during construction.
I'm immensely proud of the Metro Tunnel, which will transform the way we commute around Melbourne. Cross Yarra Partnership put sustainability at the heart of this iconic project, and Holcim enabled us to exceed our 44% cement reduction target.
Many of the mixes supplied, which now meet Holcim’s ECOPact range standards, contained high proportions of recycled materials to significantly reduce the carbon intensity of the concrete. And all of Holcim’s products in Australia are also backed by EPD’s – to help customers fully understand the life cycle impacts of their projects and make more sustainable choices.
Working with a team of researchers from the University of Melbourne and industry partners, Holcim also developed a concrete mix that substitutes 25% of the industrial sand used in concrete production for recycled crushed glass, with no reduced effects in strength or performance.
This mix was used to build temporary concrete “blinding” slabs as part of the construction of the primary structure at the new State Library Station.
It’s the first time this award-winning circular innovation was used in structural-grade concrete in an infrastructure project anywhere in the world, having previously been limited to footpaths and local roads.
With Holcim we’ve developed structural grade concrete mixes which replace 25 to 50% of the virgin sand with processed glass waste. This is the first time the 25% mix has been used on an industrial scale for a major infrastructure project.
THE ICON
Today, the twin 9 kilometer tunnels under Melbourne’s central business district are freeing up space, so more trains can travel across the city. The five new stations boast 6-star Green Star design accreditation from the Green Building Council of Australia, making them some of the most sustainable railway stations in the world.
By providing extra capacity and connectivity, the city of Melbourne will encourage more people to choose electrified trains rather than cars for their journeys, reducing emissions on the road and in Melbourne’s transport system as a whole and supporting the city’s 2030 vision for growth.
Holcim got involved primarily because the project was innovative, and stretched the industry's expectations of what low-carbon concrete looks like. We're pretty proud that we not only achieved the cement reduction target, but exceeded it.
Our stories
