The construction and building industry contributes significantly to humanity’s collective carbon footprint. Concrete alone accounts for 8% of global carbon emissions. Still, concrete is widespread, integral, and not going anywhere anytime soon. To meet the conditions of the Paris Agreement, we need to reduce concrete’s annual emissions by at least 16% by 2030. We need to make concrete more sustainable.
Valued for its strength and durability, concrete is the most widely used human-made material in the world. It’s also inherently brittle. It was, for example, a major weak link in the recent Florida condo collapse, which might have the average apartment-dweller on edge.
There are plenty of opportunities to improve the environmental and structural performance of concrete, which will be key to building more sustainable homes, offices, and infrastructure.
Making More Sustainable Concrete
Viewed from one angle, concrete is sustainable and flexible, with many applications. Some, however, see it as the most destructive material on earth. We need to address its downsides, which include carbon dioxide emissions from production, transportation, and repair.
Waste CO2 as Part of the Value Chain
In recent years, companies have been working on solutions to remove excess CO2 from the atmosphere. Two such 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 lower-carbon alternative. CUT’s CO2-embedded concrete additive sequesters CO2 into solid-waste feedstocks like fly ash, steel slag, or crushed glass, thereby also upcycling other industry byproducts. In this way, explains Chief of Staff Madison Savilow, CUT is “both a carbon utilization company and a waste management company.”
CUT’s goal is to incentivize sustainable concrete processing through a transparent profit chain. CUT encourages companies to invest in carbon capture technologies that allow them to generate revenue by selling their waste CO2. For concrete producers, CUT’s additives provide a cost-neutral option. Check out Savilow’s conversation with Earth911’s Mitch Ratcliffe during the Foundation for Climate Restoration’s Second Annual Climate Restoration Forum.
CUT both lowers concrete’s 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 by any carbon utilization company in the ready-mix concrete industry.”
Self-Healing Concrete That Prolongs the Life of Structures
Over time, concrete becomes vulnerable to fissures that put its structural integrity at risk. To solve this problem, Worcester Polytechnic Institute Associate Professor Nima Rahbar and his team, who specialize in bioinspired materials design, have 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 in small cracks within 24 hours of application.
Beyond increasing the life of concrete, Rahbar’s solution could reduce concrete’s carbon footprint. He estimates a reduction of total CO2 emissions by 30% due to a reduced need to produce new concrete and replace damaged concrete, plus a corresponding reduction of transport emissions.
“If tiny cracks could automatically be repaired when they first start, they won’t turn into bigger problems that need repair or replacement,” says Rahbar. “It sounds sci-fi, but it’s a real solution to a significant problem in the construction industry.”
Researchers have worked on similar “self-healing” alternatives involving bacteria. But Rahbar believes there are more drawbacks than benefits: The bacteria are smelly and take longer to heal cracks. Plus, we don’t 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 that ability will wear off after about six months. It can also be applied as a paste to small cracks. This might be more effective as it can be repeated indefinitely.
Rahbar says his “sci-fi” solution has the potential to prolong the life of concrete-based structures from 20 to 80 years.
What You Can Do To Support Similar Solutions
Civil engineers typically don’t get feedback from the “users” of their buildings. It’s not as easy to share your thoughts with them as with, say, your contractors. “Consumers should speak with their cities and require their town manager and mayor to build beautiful things that are designed to last a long time, are not energy-intensive, and that create money for the city,” Rahbar recommends.
Are you planning on building a house or structure yourself? If so, “The best way to support our solution and other building technologies is to ask your concrete manufacturer to spec our product,” says Savilow. (Rahbar is currently patenting his “self-healing” solution for use by construction companies; consumers could theoretically buy the paste for small-scale home repairs in the future.) You can also consider a net-zero option that uses passive design principles, incorporate insulating concrete forms (ICFs), or opt for a LEED-certified pre-fab home.
If you’re currently building, start with our guide on how to properly dispose of construction waste. Concrete can be recycled and reused in aggregate materials, and current concrete alternatives include HempCrete, AshCrete, and TimberCrete.