Engineers at RMIT University in Australia have developed a low-carbon concrete that can recycle double the amount of coal ash compared to current standards, while halving the amount of cement required. This innovative solution not only addresses the pressing issue of coal ash waste but also tackles the carbon footprint of cement production, which accounts for 8% of global carbon emissions.
Unlocking the Potential of Underutilized Pond Ash
The team’s approach goes beyond the use of fly ash, which is commonly used in low-carbon concretes. By adding nano additives to modify the concrete’s chemistry, they have managed to substitute up to 80% of the cement with coal fly ash, a significant improvement over the typical 40% replacement in existing low-carbon concretes.
Moreover, the researchers have found that their method can also harvest and repurpose lower-grade and underutilized ‘pond ash’ from coal slurry storage ponds at power plants, with minimal pre-processing. “It’s exciting that preliminary results show similar performance with lower-grade pond ash, potentially opening a whole new hugely underutilized resource for cement replacement,” said Dr Chamila Gunasekara, the project lead from RMIT’s School of Engineering.
Pioneering Modelling Technology Predicts Long-Term Performance
To ensure the long-term resilience of their low-carbon concrete, the researchers have developed a pilot computer modelling program in partnership with Hokkaido University’s Dr Yogarajah Elakneswaran. This physics-based model predicts how the low-carbon concrete will perform over time, offering opportunities to reverse engineer and optimize mixes from numerical insights.
“We’re able to see, for example, how the quick-setting nano additives in the mix act as a performance booster during the early stages of setting, compensating for the large amounts of slower-setting fly ash and pond ash in our mixes,” Gunasekara explained. “The inclusion of ultra-fine nano additives significantly enhances the material by increasing density and compactness.”
This modelling technology marks a crucial stride towards digitally assisted simulation in infrastructure design and construction, instilling confidence among local councils and communities in adopting novel low-carbon concrete for various applications.
‘Unified hydration model for multi-blend fly ash cementitious systems of wide-range replacement rates’ is published in Cement and Concrete Research (DOI: 10.1016/j.cemconres.2024.107487)
‘Sulphate and acid resistance of HVFA concrete incorporating nano silica’ is published in Construction and Building Materials (DOI: 10.1016/j.conbuildmat.2023.132004)
‘Long term mechanical performance of nano-engineered high volume fly ash concrete’ is published in Journal of Building Engineering (DOI: 10.1016/j.jobe.2021.103168)
Keyword phrase: low-carbon concrete using recycled coal ash
