Cementing CO₂ into C-S-H: A step toward concrete carbon neutrality

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Ordinary Portland cement production is a major source of greenhouse gas emissions, posing a challenge to achieving 2050 carbon neutrality goals.
• Current mitigation strategies for cement production emissions are insufficient to meet global carbon reduction targets.

Purpose of the Study:

• To investigate the mechanisms and chemomechanics of early-stage cement carbonation for CO2 sequestration.
• To evaluate the potential of direct gaseous CO2 sequestration in concrete through forced carbonate mineralization.

Main Methods:

• Integrated correlative time- and space-resolved Raman microscopy.
• Indentation approach to study cement carbonation.
• Used bicarbonate-substituted alite as a model system over hours to days.

Main Results:

• Early-stage carbonation forms calcium carbonate polymorphs (ikaite, vaterite, calcite) and a calcium carbonate/calcium-silicate-hydrate (C-S-H) composite.
• This process accelerates cement curing without compromising structural integrity.
• Significant CO2 uptake (up to 15 w%) into the cementing matrix was achieved.

Conclusions:

• Out-of-equilibrium carbonation during the precure stage offers a viable method for CO2 sequestration in concrete.
• This approach reduces the environmental footprint of cementitious materials by enabling long-term anthropogenic CO2 storage.