Concrete as a Carbon Sink?

The cement industry emits large quantities of climate-damaging carbon dioxide, but alternative binders based on magnesium carbonate could actually bind CO₂. A research project is preparing the practical application.

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More than four billion metric tons worldwide per year, and rising: Cement is by far the most widely used building material, and its production from burnt lime inevitably releases large quantities of the CO₂ bound in it. Manufacturers around the world have already significantly reduced this proportion, and the more global warming progresses, the more urgently alternatives are sought.

Cements that are not based on limestone (CaCO₃ ) but on magnesium carbonates are a source of hope. Empa experts have been researching such binders for years on the basis of the mineral olivine, which is for example available in large quantities in Norway. Magnesium oxide obtained from this magnesium silicate can be processed with water and CO₂ to produce cement. The bottom line is that more carbon dioxide is bound than emitted – in other words, a carbon sink.

But unlike conventional cements, whose hardening has been researched down to the last detail, these materials still raise many questions. The research project "Low Carbon Magnesium-Based Binders" led by Empa expert Barbara Lothenbach should soon provide answers – thanks to an Advanced Grant from the Swiss National Science Foundation with a funding of 2.2 million Swiss francs.