In a breakthrough for sustainable construction, RMIT University and Bristile Roofing have developed eco-friendly roof tiles that incorporate coal ash and recycled glass to achieve lower CO2 emissions compared to conventional concrete tiles. This research collaboration seeks to repurpose industrial waste into high-performance building materials that meet Australian safety and durability standards.

Full-scale manufacturing trials at Bristile Roofing’s Melbourne facility have produced hundreds of these sustainable roof tiles, confirming both environmental and engineering benefits. A comprehensive circular life cycle assessment of the new tiles, covering the entire process from raw material production through to end-of-life landfilling, shows a 13% reduction in CO2 emissions compared to conventional concrete tiles.

RMIT_Bristile_Roofing_sustainable_roof_tiles (3).jpg — *The manufacturing trials at Bristile Roofing’s Melbourne facility*

“By replacing 10% of cement with harvested pond ash and 10% of river sand with unwashed glass waste – a total of 20% virgin material replacement – we not only reduce waste going to landfill but also produce an improved concrete product with enhanced fire resistance, a valuable feature for roofing in Australia’s climate,” RMIT project lead, Dr Chamila Gunasekara explains.

With Australia generating 12 million tonnes of coal ash and 1.3 million tonnes of glass waste annually, this innovation represents a significant solution for industrial waste management.

The trial proves that significant volumes of this industrial waste can be reused without compromising quality and safety, says RMIT Principal Research Fellow, Dr Yulin Patrisia.

“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.”

“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.”

RMIT_Bristile_Roofing_sustainable_roof_tiles (2).jpg — *Dr Yulin Patrisia holds one of the tiles*

The product’s engineering performance is described in Sustainable Materials and Technologies, while the environmental assessment has been published in The International Journal of Life Cycle Assessment.

Building on the success, the research team is now partnering with local councils and industry to test the roof tiles in real-world projects.

Beyond roofing, the research has broader applications with the team having prototyped concrete bricks using 15% harvested pond ash and 20% unwashed glass sand – totalling 35% waste materials – while satisfying Australian standards for loadbearing structural concrete and fire performance for wall elements.

Analysis reveals these waste materials improve insulation, reducing heat loss by 30% compared to conventional cement bricks, while whole life cycle assessment demonstrates an 18% reduction in CO2 emissions through material substitution and avoided impacts.

Manufacturing trials for the concrete brick product will soon begin in collaboration with an industry partner.

Main image: RMIT's Dr Yulin Patrisia, Bristile Roofing's Samantha So, RMIT's Dr David Law and student Madushan Mudiyanselage at the Bristile factory in Dandenong

Architecture News & Editorial Desk

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