The challenge of making concrete more sustainable has taken a significant leap forward thanks to the work of a team of Australian researchers. At RMIT University, the group led by Chamila Gunasekara managed to develop a new low-emission concrete mix which uses 80% fly ash and pond ash, thus halving the cement content compared to current versions of green concrete.
The key to this success? The use of nano-additives that modify the chemistry of this material, allowing the ash percentage to be increased without compromising engineering performance.
The importance of recycling coal ash
Fly ash, or fly ash, is a residue from the combustion of coal. It is estimated that in 2022 alone, coal-fired power plants generated more than 1,2 billion tons of this material. Even though many countries are abandoning coal in favor of renewable energy sources, the ash produced so far will remain for decades and must be reused on a large scale.
The construction industry already uses bricks and concrete made from coal ash to reduce CO2 emissions. However, Gunasekara and his team's research (I link it to you here) can further help the industry reduce its carbon footprint.
Not only fly ash, but also pond ash
RMIT researchers didn't just reuse fly ash. They also worked with pond ash, or pond ash, an underused form of fly ash found in settling ponds near power plants. This material requires minimal processing before it can be used.
Compared to fly ash, pond ash is little used in construction due to its different characteristics. There are hundreds of megatonnes of waste ash in Australian dams, and much more globally.
Chamila Gunasekara
Using this material, considered an environmental hazard, as a building component is therefore a victory on all fronts.
Asha Development Association Australia
Nano-additives to improve the performance of low-emission concrete
“The inclusion of ultra-fine nano-additives significantly improves the material, increasing its density and compactness,” says Gunasekara. “Adding nano-additives to modify the concrete chemistry allows more fly ash to be added without compromising engineering performance.”
The team made large concrete beams using fly ash and pond ash in the low-emission concrete mix, demonstrating they meet Australian engineering and environmental regulations.
A predictive model to guarantee durability over time
One of the challenges in using new materials is proving that they are durable and do not deteriorate rapidly over time. To address this problem, RMIT researchers have developed a physics-based model to predict the long-term performance of low-emission concrete structures.
The model, developed in collaboration with Yogarajah Elakneswaran of Hokkaido University in Japan, allows predicting the performance of new concrete mixes over time.
Thanks to the model results, researchers can optimize mixtures to improve their performance. “We are able to see, for example, how fast-setting nano-additives act as a booster in the early setting stages, compensating for the large quantities of fly ash and slower-setting tin,” explains Gunasekara.
New low-emission concrete: towards large-scale adoption
The team plans to use these digital simulations to instill confidence in their technology and encourage communities and local governments to adopt low-emission concrete.
The research, conducted at the ARC Industrial Transformation Research Hub as part of the project TREMS (Transformation of Reclaimed Waste Resources to Engineered Materials and Solutions for a Circular Economy), represents an important step forward towards a more sustainable construction sector.
Halving the cement content in concrete, one of the most used materials in the world, can have a huge impact on reducing greenhouse gas emissions. At the same time, reusing huge quantities of waste ash helps solve a long-standing environmental problem.
Now the challenge is to bring this technology from the laboratory to the construction site, overcoming the inevitable resistance to change and demonstrating its feasibility on a large scale. But with such promising results, low-emission concrete could soon become the new standard for the construction industry, in Australia and around the world.
