ACCIONA has recently completed its first concrete pours using calcined clay mixes across Clarinda and Monash sites, as part of the Suburban Connect Project in Victoria, marking a significant step toward reducing carbon emissions in construction through the adoption of alternative supplementary cementitious materials.

Andrew Kovacs, ACCIONA’s Sustainability Manager at Suburban Connect, said collaboration was driving the initiative.

"We are generating demand, sharing lessons learned with our industry partners and encouraging the use of more sustainable products industry-wide," Mr Kovacs said.

"In the same way fly ash and slag are business-as-usual alternatives, we aim to add calcined clay to the list." He said.

Last month, more than 250 cubic metres of calcined clay concrete were poured on project sites in Clarinda and Monash. The milestone reflects ACCIONA's continued focus on lowering emissions associated with cement, which remains one of the largest contributors to the carbon footprint of traditional concrete. While slag and fly ash have long served as common alternatives to reduce cement content, both materials are increasingly difficult to source in Australia and internationally, placing pressure on supply chains and pricing.

Suburban Connect began working closely with concrete suppliers in 2024 to identify feasible low carbon options suitable for non-structural applications. This process supported the development of several mix designs that reduce reliance on conventional cement.

Calcined clay, which has been used in Europe for decades, was identified as a promising alternative due to its lower carbon intensity and stable supply potential. The material aligns with ACCIONA's sustainability and carbon reduction objectives by lowering cement content, strengthening local supply resilience and reducing dependence on by-products that are becoming scarce.

The calcined clay supplied for the recent pours was sourced from Ballarat, supporting regional Victorian industry. This direct demand from Suburban Connect has contributed to the expansion of local supply capability, reinforcing ACCIONA's broader aim of encouraging market adoption. Teams across engineering, construction and sustainability played key roles in trialling, refining and implementing the new mixes, creating a model for future applications.

The introduction of calcined clay also presents wider benefits for the construction sector. Reduced carbon intensity supports emissions targets, while a diversified supply chain helps mitigate risks associated with shrinking slag and fly ash availability. Early results from the project demonstrate that the mix performs effectively in non-structural contexts, creating opportunities for broader use as industry familiarity grows.

ACCIONA's teams are continuing to assess locations across the project where additional sustainable concrete mixes may be incorporated. This work forms part of a long-term strategy aimed at embedding low carbon materials into mainstream construction practices, supporting both environmental objectives and the development of resilient regional supply networks.