In an innovative push toward sustainable infrastructure, Major Road Projects Victoria (MRPV) has helped develop a low-carbon concrete mix using calcined clays.
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% 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 8% 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, our low carbon mix produced for this project has reduced the emissions of traditional concrete by up to 25% depending on the cement used. This is conservative and there are numerous opportunities to improve efficiency and push these reductions even further.
The use of calcined clay as a cement alternative supports Victorian Infrastructure Delivery Authority’s Transport Infrastructure Decarbonisation Strategy, which aligns with the 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, developed the mix that successfully combines 30% calcined clay with 70% traditional cement mix.
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.