Sustainable Construction: The Potential of Recycled Concrete is Significant
Recycling raw materials from used products has been contributing significantly to resource conservation and environmental relief for years. The reuse of demolition concrete, by contrast, remains relatively sparse. Yet the increasing volumes of old concrete, which contain many natural raw materials such as gravel and sand, offer considerable potential. The German Federal Environmental Foundation and the Berlin State Administration are currently engaged in various projects exploring the use of recycled concrete for building construction. In this way, up to 20 percent of CO₂ emissions can be saved. Crushed old concrete has the same technical properties and appearance as normal concrete (Source).
For Committed Companies: Cement from Regional Waste
The University of Trier is currently pursuing a more regional approach to obtaining cement from waste products. Researchers in the Geology Department are investigating the extent to which waste from sand and gravel extraction, dusts from quartz production, and residues from limestone mining—all so-called industrial secondary raw materials—can be utilized. Those are identified that have similar properties to carbonate rocks used in cement production. When these are replaced, CO₂ emissions are reduced considerably. Currently, the study is examining whether raw material reserves available in the region of Germany and Luxembourg, Belgium, and France are sufficient for forward-looking cement production. If the results are positive, the production of eco-cement could also prove economically viable for committed companies. Sustainable construction with cement would then no longer be a contradiction in terms. (Source)
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Plus for the Carbon Footprint: Less CO₂ Through Lower Temperature
One more research result before looking at already practical implementations: Scientists at Nanyang Technological University in Singapore have developed a cement from waste products that not only produces lower CO₂ emissions in its manufacturing process but is also more cost-effective than normal cement. Industrial carbide sludge serves as the base, which is mixed with acid to form calcium. This is blended with urea. Subsequent treatment with bacteria ensures that the biocement achieves material stability equivalent to ordinary cement. The special feature of this process, however, is that it can be performed at room temperature—the typically required very high temperatures with their corresponding emissions are therefore eliminated. The process has not yet reached market maturity, but it does offer prospects for sustainable construction in the near future.
Positive Reversal: A Cement That Consumes CO₂
The experimental phase is long behind American company Solidia. According to its own statements, the cement and concrete technology company saves 1.5 gigatons of CO₂ and three trillion liters of drinking water annually through a new cement manufacturing process. The core of the 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 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 offset, the CO₂ balance of cement is reduced by 70 percent. Sustainable construction 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 kilometer of road can permanently consume in a short time the exact amount of CO₂ that approximately 100,000 trees need for a year." (Source)
Geopolymer Concrete: Did the Pyramid Builders Already Know This Principle?
A fairly new alternative to CO₂-heavy cement may possibly have ancient roots: Many archaeologists who investigate the pyramid construction in Egypt 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 binding. Such geopolymers are now considered a (lime-free) alternative to traditional Portland cement.
Geopolymer concrete saves up to 70 percent of CO₂ emissions while possessing equivalent mechanical properties. Residues from existing industrial processes, such as furnace slag or fly ash, can be used to produce the geopolymers—making the process both ecologically and economically attractive. For everyone who wants to build sustainably.
What does this mean for klarx?
Although klarx does not manufacture cement, we naturally consider what impact we and the entire construction industry have on climate change. With the ambitious goal of climate neutrality in Germany in mind, we want to do our part by compensating all unavoidable CO₂ emissions through ClimatePartner and also optimizing delivery routes for our customers to save time, money, and CO₂ through shorter shipping distances. Are you wondering how you can make your construction project more sustainable? Our climate officers at klarx are happy to answer your questions about sustainability in machinery rental: sustainability@klarx.com
