K4 - Carbon dioxide reduction through low-lime clinker and carbonation hardening in concrete production

Sustainable management is a principle of the cement industry. The central tasks of this energy-intensive industry are to optimise the CO₂ balance and increase energy efficiency. In the cement industry, new paths must be taken to make concrete CO₂-neutral. This means that the CO₂ reduction strategy must combine measures in all process stages: in clinker, cement and also concrete production.

The K4 project combines the direct avoidance of process-related CO₂ emissions (Carbon Direct Avoidance) in clinker production and the permanent integration of carbon dioxide in concrete through carbonation hardening. The project focuses on the development of low-calcium clinker from recycled cement paste (RCP), which has so far received little attention as a raw material for clinker production. In contrast to the limestone otherwise used, the largely CO₂-free RCP avoids CO₂ emissions in clinker production. The use of recycled cement paste opens up a significant CO₂ reduction potential of 530 kg CO₂ per tonne of clinker - this corresponds to 63 percent of the CO₂ emissions released in cement clinker production. Another advantage of low-calcium clinker is its low calcium requirement. This maximises the CO₂ reduction potential in cement production and conserves resources.

New process in concrete hardening - for lower CO₂ emissions

In the further processing of the low-CO₂ cements into sustainable concrete products, K4 aims to develop a new type of hardening process. This enables large quantities of carbon dioxide to be permanently incorporated into the finished product during concrete hardening. The goal of the new process: the annual reduction of about 1.7 million tonnes of CO₂ emissions by avoiding and permanently incorporating carbon dioxide. This active reduction of CO₂ emissions enables the German cement industry to remain competitive even in the face of far-reaching reductions in EU emission certificates. In this way, K4 contributes both to sustainable cement and concrete production and, on a social and economic level, directly to the preservation of Germany as a production and science location.

The Federal Ministry of Education and Research is funding K4 within the KlimPro-Industrie measure with 2.6 million euros.

Project coordination

Dr. Peter Blaum
HeidelbergCement AG
Oberklamweg 2-4, 69181 Leimen

Phone: +49 6221 481 13 674
E-Mail: Peter.Blaum@heidelbergcement.com 

Dr. Martina Dietermann

Phone: +49 6221 481 13 719
E-Mail: Martina.Dietermann@heidelbergcement.com