Making concrete more sustainable – Earth911

The construction and building industry contributes significantly to humanity’s collective carbon footprint. Concrete alone accounts for 8% of global carbon emissions. Yet the concrete is widespread, integral and not going anywhere anytime soon. To meet the conditions of the Paris Agreement, we need to reduce annual emissions from concrete by at least 16% by 2030. We need to make concrete more sustainable.

Appreciated for its strength and durability, concrete is the most widely used man-made material in the world. It is also inherently brittle. It was, for example, a major weak link in the recent Florida condo collapse, which could have the average apartment dweller on edge.

There are many opportunities to improve the environmental and structural performance of concrete, which will be essential for building more sustainable homes, offices and infrastructure.

Making concrete more durable

Viewed from an angle, concrete is durable and flexible, with many applications. Some, however, consider it the most destructive material on earth. We need to tackle its drawbacks, including carbon dioxide emissions from production, transportation and repair.

CO2 waste as part of the value chain

In recent years, companies have been working on solutions to remove excess CO2 from the atmosphere. Two of these companies, Blue Planet and Carbon Upcycling Technologies (CUT), have developed methods to capture and use atmospheric carbon dioxide by turning it into a valuable and economically viable building material. In other words, one of the raw concrete.

Concrete is made by combining cement with water to form a paste, then adding aggregates like sand or gravel. CUT, however, manufactures a low carbon alternative. CUT’s CO2-encrusted concrete additive sequesters CO2 in solid waste raw materials such as fly ash, steel slag or crushed glass, thereby also upgrading other by-products of the industry. So, explains Chief of Staff Madison Savilow, CUT is “both a carbon utilization company and a waste management company.”

The goal of CUT is to encourage the sustainable transformation of concrete through a transparent profit chain. CUT encourages companies to invest in carbon capture technologies that allow them to generate income by selling their waste CO2. For concrete producers, CUT additives offer a cost neutral option. Check out Savilow’s conversation with Earth911’s Mitch Ratcliffe at the Foundation for Climate Restoration’s second annual Climate Restoration Forum.

CUT both reduces the concrete footprint and increases its longevity. “Our additives reduce the carbon impact of concrete manufacturing by up to 25% while improving the strength of concrete by up to 40%,” says Savilow. “This is the highest carbon reduction of any company using carbon in the ready-mixed concrete industry. “

Self-healing concrete that prolongs the life of structures

Over time, concrete becomes vulnerable to cracks that endanger its structural integrity. To solve this problem, Worcester Polytechnic Institute Associate Professor Nima Rahbar and his team, specializing in the design of bioinspired materials, created a “self-healing concrete” using carbonic anhydrase (CA), an enzyme found in human blood. CA is a catalyst that reacts with CO2 to form calcium matrices that fill small cracks within 24 hours of application.

Beyond increasing the life of concrete, Rahbar’s solution could reduce the carbon footprint of concrete. It estimates a reduction in total CO2 emissions of 30% due to a reduced need to produce new concrete and replace damaged concrete, as well as a corresponding reduction in transport emissions.

“If tiny cracks could be repaired automatically as soon as they appear, they wouldn’t turn into more serious problems requiring repair or replacement,” says Rahbar. “It sounds like science fiction, but it’s a real solution to a big problem in the construction industry. “

Researchers worked on similar “self-healing” alternatives involving bacteria. But Rahbar thinks there are more disadvantages than advantages: Bacteria are smelly and take longer to heal cracks. In addition, we do not know the impact of their presence on human health.

Rahbar’s solution can be applied in two ways. When applied as a powder during concrete production, cracks will have the ability to “self-heal”. But this ability will wear off after about six months. It can also be applied as a paste on small cracks. It might be more effective because it can be repeated over and over again.

Rahbar says his “science fiction” solution has the potential to extend the life of concrete-based structures by 20 to 80 years.

What you can do to support similar solutions

Civil engineers generally do not receive feedback from the “users” of their buildings. It’s not as easy to share your thoughts with them as it is with, say, your contractors. “Consumers should speak with their cities and demand from their city manager and mayor to build beautiful things that are designed to last a long time, don’t consume a lot of energy and create money for the city,” recommends Rahbar. .

Are you planning to build a house or structure yourself? If so, “The best way to support our solution and other construction technologies is to ask your concrete manufacturer to specify our product,” says Savilow. (Rahbar is currently patenting its “self-healing” solution for construction companies; consumers could theoretically buy the paste for small-scale repairs in the future.) You could also consider a net zero option. that uses passive design principles, incorporate Insulated Concrete Forms (ICF) or opt for a LEED-certified prefabricated home.

If you are currently building, start with our guide on how to properly dispose of construction waste. Concrete can be recycled and reused in aggregate, and current alternatives to concrete include HempCrete, AshCrete, and TimberCrete.