Researchers at RMIT have teamed up with Bristile Roofing to develop roof tiles made from coal ash and recycled glass.
The innovation repurposes industrial waste otherwise headed to landfills, and instead delivers fire-resistant roofing options compliant with Australian Standards.
A full-scale manufacturing trial at Bristile Roofing’s Melbourne facility produced hundreds of these eco-friendly tiles.
A circular life-cycle assessment of them, covering the entire process from raw material production through to end-of-life landfilling, reportedly showed a 13 percent reduction in CO₂ emissions compared to conventional concrete tiles.
RMIT project lead Dr Chamila Gunasekara says the environmental benefit largely stems from using harvested pond ash and unwashed recycled glass sand, which avoids energy-intensive processing and replaces virgin materials.
“By replacing 10 percent of cement with harvested pond ash and 10 percent of river sand with unwashed glass waste – a total of 20 percent virgin material replacement – we not only reduce waste going to landfill but also produce an improved concrete product with enhanced fire resistance,” he said.
In Australia, approximately 12 million tonnes of coal ash are produced annually from electricity generation, with more than 400 million tonnes of coal ash stored in large settling ponds.
In addition, Australia generates more than 1.3 million tonnes of glass waste each year, with more than half ending up in landfills.
“While harvested waste pond ash is less reactive – primarily due to prolonged storage in settling ponds – it remains an attractive material due to its abundance and contribution to long-term engineering performance,” RMIT Principal Research Fellow Dr Yulin Patrisia says.
“Despite its lower early reactivity, it helps enhance concrete performance over time. Our tests showed better dimensional stability, reduced shrinkage cracking, and continued strength gain – making it ideal for durable, non-structural applications.”
The concrete mix design has broader applications beyond roof tiles. Another of the team’s prototypes is concrete bricks. These use 15 percent harvested pond ash and 20 percent unwashed glass sand – totalling 35 percent waste materials – while complying with Australian standards for load-bearing structural concrete and fire performance for wall elements.
Analysis found using these waste materials could also improve insulation, reducing heat loss by 30 percent compared to conventional cement bricks.
The RMIT team says it is now collaborating with local councils and commercial partners to trial the roof tiles in real-world settings.
“This is more than just a lab success,” Gunasekara says. “We are ready to scale this for industry.”
The research developments come shortly after the Australian Government set a national target to reduce emissions by 62–70 percent below 2005 levels by 2035, with a specific focus on emissions within the built environment.
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