Storing carbon dioxide in concrete without compromising strength

By using a carbonated water-based solution during the concrete manufacturing process, a team of engineers has discovered a new way to store carbon dioxide.

In laboratory experiments, the process achieved a CO2 sequestration efficiency of up to 45%, meaning that nearly half of the CO2 injected during concrete manufacturing was captured and stored. The researchers hope their new process could help offset CO2 emissions from the cement and concrete industries. The study, supported by Cemex, was published in the journal Communications Materials.

In this new approach, the researchers leveraged the fresh concrete carbonation process but, instead of injecting CO2 while mixing all the ingredients together, they first injected CO2 gas into water mixed with a small amount of cement powder. After mixing this carbonated suspension with the rest of the cement and aggregates, they achieved a concrete that actually absorbed CO2 during its manufacturing.

“The cement suspension carbonated in our approach is a much lower viscosity fluid compared to the mix of water, cement and aggregates that is customarily employed in present approaches to carbonate fresh concrete,” study leader Alessandro Rotta Loria said. “So, we can mix it very quickly and leverage a very fast kinetics of the chemical reactions that result in calcium carbonate minerals. The result is a concrete product with a significant concentration of calcium carbonate minerals compared to when CO2 is injected into the fresh concrete mix.”

After analysing their carbonated concrete, the research team found its strength rivalled the durability of regular concrete.

“A typical limitation of carbonation approaches is that strength is often affected by the chemical reactions,” Alessandro said. “But, based on our experiments, we show the strength might actually be even higher. We still need to test this further, but, at the very least, we can say that it’s uncompromised. Because the strength is unchanged, the applications also don’t change. It could be used in beams, slabs, columns, foundations‚ÄĒeverything we currently use concrete for.”

The findings of this research underline that although carbonation of cement-based materials is a well-known reaction, there is still room to further optimise the CO2 uptake through better understanding of the mechanisms tied to materials processing, according to the team.

Read more at: Storing CO2 while strengthening concrete by carbonating its cement in suspension.

About the author

Desi Corbett

Desi is the Editor of Concrete in Australia and at the helm of our magazine for 8 years. She was behind the Institute's weekly news bulletins from 2016-2021 and is now writing our focused news items. Desi has been an engineering news and features journalist/editor across all disciplines since 2013 - part of a 30-year career writing for a wide range of industries.