Major Road Projects Victoria (MRPV) has helped develop a low-carbon concrete mix using calcined clays, furthering sustainable practices in infrastructure.
MRPV, Arup, The University of Melbourne and Hanson Australia developed the mix in a joint project that successfully replaced concrete’s cement binder with up to 30 per cent calcined clays.
Concrete, a core material in construction, traditionally comprises cement, sand, gravel and water. However, cement is a major contributor to global carbon emissions, responsible for around eight per cent of total CO2 emissions worldwide.
Cement production requires significant energy, and the chemical processes involved in manufacturing releases large amounts of CO2, making it one of the most carbon-intensive materials used in construction.
To address this, MRPV and its partners explored the incorporation of calcined clays in concrete to replace some of the traditional cement used.
Calcined clays are produced by heating certain types of clay between 600°C and 900°C, altering their chemical structure to create a reactive material capable of binding together the concrete.
Importantly, the production of calcined clay for this project resulted in approximately 50 per cent of the carbon emissions compared to cement, offering a more-sustainable option for the construction industry. Improvements to the calcined clay process could see this carbon factor drop even further.
The use of calcined clay as a cement alternative supports the Victorian Infrastructure Delivery Authority’s Transport Infrastructure Decarbonisation Strategy, which aligns with Victoria’s Climate Change Act and the State Government’s net-zero 2045 ambitions.
The preliminary joint research project with the University of Melbourne and Arup enabled the identification of suitable clays from an aggregate washing process, after which the remaining clay would have otherwise been returned as fill material.
After analysing the clays, a viable type was selected and heated to 650°C in a full-scale rotary kiln by Renex at their facility in Dandenong South.
In partnership with the research and development laboratory of Hanson Australia, the team developed a concrete mix with 30 per cent calcined clay in the binder.
Extensive testing of the concrete mix was completed to ensure it met industry standards.
Testing has shown that the mix exceeded the target compressive strength of 32 MPa at 28 days, a key benchmark for structural concrete.
Additionally, the mix demonstrated workability and durability, confirming its suitability for large-scale infrastructure projects.
MRPV is using the new mix on the Mickleham Road Upgrade at Greenvale in Melbourne’s north.
Major Road Projects Victoria Director Engineering and Innovation, Dr Scott Taylor, said, “We’re thrilled with the success of this ground-breaking initiative with Arup, The University of Melbourne and Hanson to develop a new low-carbon concrete mix using calcined clay.”
“The mix reduces the amount of carbon dioxide emissions associated with producing concrete, which will help support future opportunities to decarbonise the construction industry across Australia.”
University of Melbourne Faculty of Engineering and Information Technology Senior Lecturer, Dr Rackel San Nicolas, said, “Calcined clay concrete is one of the most promising technologies for the future of concrete in Victoria and Australia, and it’s exciting that we can now demonstrate its feasibility in the field.”
“We’re so pleased to be working collaboratively with the government and our industry partners towards providing a sustainable solution for the future of construction.”
Arup Senior Materials Engineer, Dr Fangjie Chen, said, “This project underscores Arup’s commitment to reducing the carbon footprint of concrete. By connecting our client, researchers, and our supply chain partner, we’ve successfully developed a calcined clay concrete mix that not only meets project requirements but also aligns with broader environmental objectives, paving the way for more sustainable construction practices across Australia.”
