Microstructural Densification and CO2 Sequestration by the Carbonation Curing of Belite Cement
Stable isolation of CO2 in belite-rich cement
Concrete is the most common construction material that is produced and consumed by the largest amount across the world. Cement is the main element and the only artificially produced material used in manufacturing concrete. However, during the production of cement, a large amount of carbon dioxide is emitted, which is 5% to 8% of the total amount emitted from the industry as a whole.
Since CO2 is a well-known culprit of global warming, studies concerning various means of reducing CO2 emissions or to capture (store) and utilize the emitted CO2 have been actively conducted. Over the past several decades, the cement industry has been keen to reduce CO2 emissions from the cement manufacturing process. In particular, the concrete industry has also been engaged in serious efforts to reduce the CO2 generated in the concrete manufacturing process by recycling industrial by-products, expanding the use of blended cement, and developing cement-free binders. Even more active attempts have been made recently; one of those is isolating captured CO2 through carbonation curing of concrete.
Against this backdrop, Prof. H.K. Lee and his team successfully developed technology that utilizes captured CO2 in the curing process of concrete, thereby increasing the strength and durability of concrete and providing means of stable isolation of CO2.
The team first came up with the idea from the fact that hydrated cement paste, which makes up concrete, absorbs CO2 in the atmosphere by a chemical reaction called carbonation. Then, the team carried out studies on the carbonation reaction of dicalcium silicate (belite, 2CaO·SIO2), which has a low hydraulic reactivity, in the clinker minerals of cement with the support of the Saudi Aramco-KAIST CO2 Management Center.
Through the research, Prof. Lee and his team found the mechanism where CO2 is provided in the curing process of concrete to carbonate belite phase, leading to the microstructural densification and improving the strength and durability of concrete.
In addition, they also found that 16.9% of CO2 relative to the weight of the cement used can be sequestrated inside concrete by using belite-rich cement. This result has attracted great interest in the academic community. Last April, this study was published in Cement and Concrete Research, a prestigious journal in the field of construction materials.
This study has great significance in that cement-concrete, which has not been exactly recognized as an eco-friendly material, has been suggested as a medium that can isolate a large amount of CO2. The team plans to apply this technology to industrialization through joint research with the Saudi Aramco-KAIST CO2 Management Center.
Prof. Lee, Haeng Ki
2016 Annual Report