CORE – Resource-efficient and climate-optimised concrete in Berlin

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In order to reduce high greenhouse gas emissions and resource consumption in the construction sector, the state of Berlin is focusing on the use of sustainable building materials and circular construction.

The company neustark has developed a novel process in which CO₂ is stored in RC aggregate through accelerated carbonation. The Berlin Senate Department for the Environment, Mobility, Consumer Protection and Climate Protection (SenUMVK) has set itself the goal of further improving the climate balance of resource-saving concrete. For this reason, it has joined forces with the companies Heim Recycling, neustark, Berger Beton and ifeu Heidelberg to launch the ‘CORE (CO2-reduced concrete)’ project, which will pilot the neustark process in the Berlin area.

As part of the project, old concrete crushed into RC aggregate by Heim was exposed to CO₂, which is converted into limestone in the pores and on the surface of the RC aggregate through carbonation. If these RC aggregates are used in concrete mixes, the cement content can also be reduced, which makes concrete production significantly more climate-friendly overall.

As part of the project, certification and approval as an aggregate for use in ready-mixed concrete has now been obtained for this carbonated RC aggregate for the first time. The same regulations (DIN EN 12620) apply as for the use of gravel or grit.

According to calculations by ifeus, the formulations developed can achieve a relevant reduction in environmental impact across all environmental impact categories considered. The effort involved in supplying the CO₂ and applying it to the RC aggregate is in good proportion to the associated environmental savings. The environmental savings result from the reduction in cement quantities and the CO₂ binding achieved through carbonation. Compared to the reference sample, the climate impact of the resource-saving concrete can be reduced by up to 20% through the treatment of the RC aggregate.

This CO₂-reduced and resource-saving concrete is now set to be used for the first time in autumn this year, in compliance with all relevant standards, in a construction phase of the Friedenauer Höhe district development in Berlin-Friedenau, which is being realised in a joint venture with OFB Projektentwicklung and Instone Real Estate.