Sustainable Building: The Potential of Recycled Concrete is Substantial
Recycling raw materials from used products has been contributing significantly to resource conservation and environmental relief for years. By contrast, the reuse of demolition concrete remains comparatively sparse. Yet the rising quantities of old concrete, which contain many natural raw materials like gravel and sand, offer considerable potential. The German Environmental Foundation and the Berlin Senate Administration are currently engaged in various projects exploring the use of recycled concrete for building construction. This way, up to 20 percent of CO₂ emissions can be saved. Crushed old concrete has the same technical properties and appearance as standard concrete (source ).
For Committed Companies: Cement from Regional Waste
The University of Trier is currently pursuing a more regional approach to producing cement from waste materials. Researchers in the Department of Geology are investigating how waste from sand and gravel extraction, dust from quartz production, and residues from limestone extraction—all so-called industrial secondary raw materials—can be utilized. Those are identified that have similar properties to the carbonate rocks used in cement production. When these are replaced, CO₂ emissions are reduced considerably. Currently, investigations are underway to determine whether the raw material reserves available in the regions of Germany and Luxembourg, Belgium, and France are sufficient for future cement production. If the result is positive, eco-cement production could also make economic sense for committed companies. Sustainable building with cement would no longer be a contradiction. (source )
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A Plus for the Carbon Footprint: Less CO₂ Through Lower Temperature
One more research finding before turning to already practical implementations: Scientists at Nanyang Technological University in Singapore have succeeded in developing a cement from waste materials whose production not only results in lower CO₂ emissions but is also more cost-effective than ordinary cement. The basis is industrial carbide sludge, which is mixed with acid to form calcium. This is then combined with urea compounds. Subsequent "treatment" with bacteria ensures that the biocement achieves material stability comparable to ordinary cement. However, the special feature of this process is that it can occur at room temperature—the normally required very high temperatures and their corresponding emissions are therefore eliminated. The process is not yet market-ready, but it does offer prospects for sustainable building in the near future using this method.
A Positive Reversal: A Cement That Consumes CO₂
The American company Solidia has long since moved past the experimental stage. Through a new cement production process, the cement and concrete technology company saves, according to its own claims, 1.5 gigatons of CO₂ and three trillion liters of drinking water annually. The core of this groundbreaking technology: Solidia has modified the chemical components of cement so that it consumes CO₂ during production instead of producing it.
The cement reacts with supplied CO₂ instead of with water. During hardening, CO₂ molecules are broken apart and the carbon is bound to produce limestone, which ultimately holds the concrete together. When this CO₂ consumption during the hardening process is offset, the carbon footprint of cement is reduced by 70 percent. Sustainable building with Solidia concrete is not yet possible—it is currently being used on a large scale for infrastructure projects. In this sense, a nice anecdote from CEO Tom Schuler: "Fundamentally, our development means that a new road kilometer can permanently consume in a short time exactly the amount of CO₂ that around 100,000 trees need a year." (source )
Geopolymer Concrete: Did the Pyramid Builders Know This Principle?
A relatively new alternative to CO₂-heavy cement may have remarkably ancient roots: Many archaeologists who study the Egyptian pyramid construction with increasingly precise techniques are now convinced that the ton-heavy blocks were at least partially cast directly on-site and made eternally durable with an alkaline-activated binder. Such geopolymers are now considered a (lime-free) alternative to traditional Portland cement.
Geopolymer concrete saves up to 70 percent of CO₂ emissions but possesses equivalent mechanical properties. Residues from existing industrial processes, for example furnace slag or fly ash, can be used to produce the geopolymers—making the process ecologically and economically attractive. For everyone who wants to build sustainably.
What Does This Mean for klarx?
Although klarx does not manufacture cement, we certainly consider what contribution we and the entire construction industry make to climate change. With Germany's ambitious goal of climate neutrality in mind, we want to do our part and, on the one hand, compensate all unavoidable CO₂ emissions via ClimatePartner and, on the other hand, also optimize transport routes for our customers to save time, money, and CO₂ with shorter delivery distances. Wondering how you can make your construction project more sustainable? Our climate officers at klarx are happy to answer your questions about sustainability in equipment rental: sustainability@klarx.com
