C²inCO₂: Calcium Carbonation for industrial use of CO₂

Sustainable reduction of CO₂-emissions

Due to the immense volumes of concrete used, the cement industry emits a significant proportion of the total anthropogenically produced CO₂. While energy-related emissions can be minimized in cement production by using for example alternative fuels, the CO₂ produced during the calcination of limestone is considered system-inherent and therefore unavoidable. The hardened cement paste or its hydrated clinker phases offer great potential for the permanent binding of CO₂. Already during the use and recycling phase of concrete, about 25 to 30 percent of the CO₂ caused by the raw material processing is bound in a natural way. The key objective of this research project is to unlock the remaining potential of recycled concrete to re-integrate the CO₂ released during calcination into limestone and to use it as a building material.

Long-term binding of CO₂ in marketable products

Within the framework of the BMBF funding measure “CO₂-WIN”, the joint project “C²inCO₂” addresses an alternative approach to CO₂ utilization based on the mineralization of fines from concrete recycling and their use in the large-scale production of novel cements and concretes. The scientific and technical development activities cover the provision and preparation of the various input materials as well as the design and construction of a pilot plant for the selective comminution and carbonation of the demolition concrete. Further, it includes the performance of practical tests for the production of new types of cements and concrete goods, as well as the detailed analysis of the products produced and their testing upon suitability for industrial application. Furthermore, these novel approaches are evaluated with reliable indicators during an ecological and economic life cycle analysis.

Development of sustainable CO₂ value-added chains

An advanced recycling technology enables the proper separation of the hardened cement paste from sand and aggregates, allowing an efficient use for carbonation. This fraction of recycled concrete fines can easily be carbonated, which facilitates for example the direct use of the CO₂ containing exhaust gases from the cement plant. The carbonated hardened cement paste is used as a clinker substitute and enables a further reduction of the clinker content in cement, preserving natural resources, and reducing CO₂ emissions. If successful, the developed concept as well as the novel cements and concretes can be used on an industrial scale after the extension of corresponding standards. The development and implementation of the concept take place within the framework of a transdisciplinary collaboration between representatives of the cement and concrete industry (HeidelbergCement AG), large-scale machinery and systems engineering firms (thyssenkrupp Industrial Solutions AG, Loesche GmbH), suppliers of construction chemical products and solutions (Sika AG) and through the involvement of renowned institutes from basic and application-oriented research (F. A. Finger Institute for Building Materials Science at Bauhaus University Weimar, Fraunhofer Institute for Building Physics, Department of Mineral Resources Processing at RWTH Aachen University).

Interview about C²inCO₂

Download the C²inCO₂ project data sheet