Model Forecasts Coal Ash Concrete Performance

MONDAY, MAY 20, 2024

New models from researchers at RMIT University in Australia has reportedly revealed that low-carbon concrete developed at the university can recycle double the amount of coal ash and halve the amount of cement required.

The results were recently published in the journal Cement and Concrete Research.

About the Study

According to the university, more than 1.2 billion tons of coal ash were produced by coal-fired power plants in 2022. In Australia, this accounts for nearly a fifth of all waste. At the same time, cement production makes up 8% of global carbon emissions and demand for concrete and is growing.

To find a potential solution for this material usage, engineers at RMIT partnered with AGL's Loy Yang Power Station and the Ash Development Association of Australia to substitute 80% of the cement in concrete with coal fly ash. 

RMIT project lead Dr. Chamila Gunasekara said this represents a significant advancement, as existing low-carbon concretes typically have no more than 40% of their cement replaced with fly ash.

"Our addition of nano additives to modify the concrete’s chemistry allows more fly ash to be added without compromising engineering performance,” said Gunasekara.

The university says that lab studies have shown the team’s approach is also capable of harvesting and repurposing lower grade and underutilized “pond ash,” which is taken from coal slurry storage ponds at power plants, with minimal pre-processing.

Large concrete beam prototypes were created using both fly ash and pond ash. They both reportedly met Australian Standards for engineering performance and environmental requirements.

“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,” Gunasekara said. “Compared to fly ash, pond ash is underexploited in construction due to its different characteristics. There are hundreds of megatons of ash wastes sitting in dams around Australia, and much more globally.

“These ash ponds risk becoming an environmental hazard, and the ability to repurpose this ash in construction materials at scale would be a massive win.”

The pilot computer modelling program developed by RMIT, in partnership with Hokkaido University’s Dr. Yogarajah Elakneswaran, has now been used to forecast the time-dependent performance of these new concrete mixtures.

Dr. Yuguo Yu, an expert in virtual computational mechanics at RMIT, said a longstanding challenge in the field has been to understand how newly developed materials will stand the test of time. 

“We’ve now created a physics-based model to predict how the low-carbon concrete will perform over time, which offers us opportunities to reverse engineer and optimize mixes from numerical insights,” Yu explained.

“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 said. “The inclusion of ultra-fine nano additives significantly enhances the material by increasing density and compactness.” 

According to RMIT, this modelling marks a “crucial stride” towards digitally assisted simulation in infrastructure design and construction. The team hopes to instill confidence among local councils and communities in adopting novel low-carbon concrete for various applications.

This research was enabled by the ARC Industrial Transformation Research Hub for Transformation of Reclaimed Waste Resources to Engineered Materials and Solutions for a Circular Economy.


Tagged categories: Asia Pacific; Building materials; Cement; Coal ash; Colleges and Universities; concrete; EMEA (Europe, Middle East and Africa); Environmental Controls; Good Technical Practice; Green building; Latin America; North America; Program/Project Management; Recycled building materials; Research and development; Z-Continents

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