Approaches for reducing CO2 in concrete for a climate-neutral construction sector

Solid Unit is celebrating its first anniversary – a network acting across Germany concerning climate-neutral construction with mineral building materials has been existing since last autumn (see also BFT 10/2022). The name Solid Unit stands for trust, reliability and strength (“solid”), but also for unity and community (“UNIT”). Together with its partners and members, the network is committed to accelerating the transformation towards a climate-neutral construction industry. The aim is to spread the knowledge of the climate protection potentials of innovative solid construction even more. For this purpose, Solid Unit promotes the dialog and the interaction among politics, science, architects/planners, start-ups and the public.

Members of Solid Unit are companies and renowned associations of the building sector and the construction industry, which are paving the way for climate-neutral construction with their flagship projects and their expertise, as well as start-ups, which contribute their innovative ideas as supporting members. The strong alliance of these players reveals: The prerequisites and the technical know-how are already available to construct future-oriented, sustainable buildings.

Moreover, in 2023, Solid Unit has established a climate advisory council, consisting of personalities from the world of planning and politics, that is to accompany the construction sector on the pathway to climate neutrality with its expertise regarding sustainable construction. Members of the climate advisory council are Prof. Lucio Blandini (Head of ILEK), Bernhard Daldrup MdB (SPD), Michael Kießling MdB (CDU/CSU), Dr. Christine Lemaitre (DGNB Executive Board Member), Dr. Tillman Prinz (Executive Director of the Federal Chamber of German Architects), Kassem Taher Saleh MdB (Alliance 90/The Greens), Prof. Dietmar Walberg (Executive Director of ARGE – the Federal Employment Agency) and Sandra Weeser MdB (FDP).

„We want to support the research for innovative new construction materials, to encourage thinking in terms of a circular economy, to optimize the energy demand of buildings, and we advocate the life cycle assessment of building structures. However, Solid Unit does not stand for the promotion of specific construction methods, but for a common approach in favor of more construction in a climate-neutral way! Therefore, it was important to us to involve young start-ups with their ideas in our network right from the beginning. Three of these companies are our Solid Unit members Alcemy, EcoLocked and Sonocrete. We want to turn the spotlight on and showcase what is already possible in terms of climate neutrality with the aid of mineral building materials,“ explains Thomas Zawalski, the Executive Director of Solid Unit.

Decarbonization of the concrete sector

The reduction of the clinker content in concrete is a big lever for the decarbonization of the construction industry. For this purpose, the Alcemy start-up has developed a software, that with the aid of AI and intelligent algorithms allows for a better control of low-clinker concretes. Using sensor technology as an interface, the software determines in factory and truck mixer important data such as effective performance curve, dosage, moisture, temperature and oil pressure, thus ensuring an end-to-end monitoring from the factory to the construction site in real time. Thanks to machine learning, exact predictions about the slump flow can be made then and the quality of low-clinker concrete can be controlled even better.

With a worldwide unique premixing concept, the Sonocrete start-up provides for better early and compressive strengths of low-clinker precast concrete elements. The company integrates a bypass process into the conventional procedure of concrete mixing, where a small portion of the cement and a portion of water are mixed to a cement suspension and are treated with the aid of high power ultrasound. This „Sonocrete effect“ allows precast concrete manufacturers to use CO2-reduced concretes without having to make any concessions on the early strength.

EcoLocked pursues another approach for reducing CO2 emissions: The company is developing admixtures based on biochar for the production of climate-neutral concrete and perhaps even climate-positive concrete in the future. For this purpose, EcoLocked processes biochar to a carbon-negative concrete admixture which enables them to substitute cement as well as sand to some extent and to improve the functional properties of the concrete. According to the manufacturer, the carbon footprint of concrete can be reduced by up to 120 % in this way. In cooperation with BNB Beton and Naturstein Babelsberg GmbH, EcoLocked has already produced the first usable climate-neutral precast concrete elements.


Solid Unit e.V.

Kronenstraße 55–58

10117 Berlin/Germany

+49 30 20314-562


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