Concrete as a Carbon Sink: CO₂-Binding Cement Substitute Aims to Transform Construction

Researchers at the Karlsruhe Institute of Technology (KIT) are developing a concrete material that could lower construction-related emissions while permanently storing carbon dioxide. The work is part of the European C-SINC project, which brings together research and industry partners from Germany, the Netherlands, Belgium, Spain, Sweden and Switzerland.

Concrete remains the most widely used building material worldwide, but the cement it contains is responsible for a significant share of global carbon emissions. Cement clinker, a key component of Portland cement, accounts for around 8% of global CO₂ emissions. These emissions arise from both the energy-intensive manufacturing process and the chemical conversion of limestone during clinker production.

Magnesium Silicates as a Cement Substitute

The C-SINC project is exploring the use of magnesium silicates as a supplementary cementitious material. Through an accelerated mineralisation process, the minerals react with captured carbon dioxide and convert it into magnesium carbonate.

Researchers can then use this carbon-rich material to replace part of the cement clinker in concrete. Unlike established alternatives such as fly ash and blast-furnace slag, which are expected to become less available as industries decarbonise, magnesium silicates could provide a long-term and scalable solution.

The process uses CO₂ captured from industrial exhaust streams. Rather than storing the carbon temporarily, the reaction locks it into a stable mineral structure. This allows the concrete to act as a long-term carbon sink while reducing emissions associated with cement production.

Testing for Real-World Construction

The project partners aim to move beyond laboratory research and accelerate the use of the material in construction applications. To support this goal, researchers are investigating how the new binder performs in both small-scale tests and full-size structural elements.

At KIT, teams use machine learning and structural modelling to optimise concrete formulations and predict performance. They then validate these predictions through experimental testing. The researchers are assessing key properties such as load-bearing capacity, durability and safety to ensure the material meets construction standards.

According to the team, combining digital modelling with large-scale testing helps identify concrete formulations that balance structural performance with a lower environmental impact.

European Research Collaboration

The four-year C-SINC project receives approximately €4 million in funding through the European Innovation Council’s Pathfinder Challenge, Towards Cement and Concrete as a Carbon Sink. The consortium includes KIT, Delft University of Technology, KU Leuven, the Spanish National Research Council, PREFABRICADOS TECNYCONTA S.L., PAEBBL AB and Holcim Technology Ltd.

If successful, the project could contribute to the development of lower-carbon concrete materials that not only reduce emissions but also actively remove carbon dioxide from the atmosphere.

Source: Karlsruhe Institute of Technology
Photo: Cynthia Ruf