Sustainable Building: Cement from Waste Materials - for a Smaller Ecological Footprint

Sustainable Building: The Potential of Recycled Concrete is Significant

Recycling raw materials from used products has contributed to resource conservation and environmental relief for years. The reuse of demolition concrete, by contrast, remains relatively limited. Yet the growing volumes of old concrete, which contains many natural raw materials like gravel and sand, offer substantial potential. The German Federal Foundation for the Environment and the Berlin Senate Department for the Environment are currently engaged in various projects exploring the use of recycled concrete in building construction. This could save up to 20 percent in CO₂ emissions. 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 products. Researchers in the geology department are investigating how waste from sand and gravel extraction, dust from quartz processing, and residues from limestone mining – all known as industrial secondary raw materials – can be utilized. From these, they identify those with similar properties to the carbonate rocks used in cement production. When these are replaced, CO₂ emissions are reduced considerably. Currently, they're examining whether the raw material reserves available in the region of Germany and Luxembourg, Belgium, and France would be sufficient for forward-looking cement production. If the result is positive, eco-cement production could also make economic sense for committed companies. Building sustainably with cement would then no longer be a contradiction in terms. (Source )

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Plus for the Environmental Balance: Lower CO₂ Through Lower Temperature

One more research finding before we look at practical implementations: Scientists at Nanyang Technological University in Singapore have succeeded in developing a cement from waste products that not only achieves lower CO₂ emissions during production but is also cheaper than standard cement. The basis is industrial carbide sludge, which is treated with acid to form calcium. This is mixed with urea. Subsequent treatment with bacteria ensures that the biocement achieves material stability equal to ordinary cement. What makes this process special, however, is that it can take place at room temperature – eliminating the normally required high temperatures and their corresponding emissions. The process isn't market-ready yet, but it does offer prospects for building sustainably this way in the near future.

Positive Reversal: A Cement That Consumes CO₂

American company Solidia has long since moved beyond the experimental phase. According to its own claims, the cement and concrete technology company saves 1.5 gigatons of CO₂ and three trillion liters of drinking water annually through a new cement production process. The core of this groundbreaking technology: Solidia has modified the chemical components of cement so that it consumes CO₂ during production rather than producing it.

The cement reacts with supplied CO₂ instead of water. During curing, the 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 curing process is factored in, the CO₂ balance of cement is reduced by 70 percent. Building sustainably with Solidia concrete isn't quite there yet – it's currently being used on a large scale for infrastructure projects. In this sense, here's a nice anecdote from CEO Tom Schuler: "Essentially, our development means that a new road kilometer can permanently consume exactly the amount of CO₂ in a short time that around 100,000 trees need a year." (Source )

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Geopolymer Concrete: Did the Pyramid Builders Know the Principle?

A fairly recent alternative to CO₂-heavy cement may have very ancient roots: Many archaeologists investigating pyramid construction in Egypt with increasingly precise techniques are now convinced that the ton-heavy blocks were at least partly cast on-site and made permanently 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 in CO₂ emissions while possessing equivalent mechanical properties. Residues from existing industrial processes, such as furnace slag or fly ash, can be used to produce geopolymers – making the process both ecologically and economically attractive. For everyone who wants to build sustainably.

What Does This Mean for klarx?

Even though klarx doesn't produce cement, we naturally think about what impact we and the entire construction industry have on climate change. With Germany's ambitious goal of climate neutrality in mind, we want to do our part and, on the one hand, offset all unavoidable CO₂ emissions through ClimatePartner and, on the other hand, 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

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