Concrete has an enormous carbon footprint. The material accounts for roughly 8% of the carbon dioxide emitted into the atmosphere, dwarfing the aviation industry’s 2.5% contribution. Therefore, technologies that extend concrete life and boost its performance could have profound benefits for the environment.
Scientists at the Worcester Polytechnic Institute (WPI) have developed self-healing concrete that can repair its own cracks. While researchers have previously produced concrete that can self-heal, the WPI team’s version uses an enzyme found in human blood and is claimed to be cheaper and more efficient.
Tiny cracks in concrete don’t pose an immediate threat to the structure of a building, but after time water seeps in, and the rupture spreads. This compromises its strength and lifespan. Self-healing concrete is designed to intervene in this process while the cracks are still small, sealing up the material to prevent anything from a catastrophic collapse to expensive maintenance or an entire replacement of the structure.
The WPI team turned to the human body for inspiration, specifically, to the enzyme in red blood cells known as carbonic anhydrase (CA) and how it can rapidly transfer CO2 from the cells into the bloodstream.
Nima Rahbar, the study’s author, said:
We looked to nature to find what triggers the fastest CO2 transfer, and that’s the CA enzyme. Since enzymes in our bodies react amazingly quickly, they can be used as an efficient mechanism to repair and strengthen concrete structures.
The scientists added CA enzyme to concrete powder before the material is mixed and poured. When the concrete forms a crack, the enzyme interacts with CO2 to create calcium carbonate crystals, which imitate the characteristics of concrete and promptly fill in the gap.
In lab tests, the team demonstrated that the concrete containing the enzyme could repair its millimeter-scale cracks within 24 hours. According to the WPI scientists, this is a noticeable improvement on some previous technologies that use bacteria for self-healing, which can take up to a month to heal and are more expensive.
The amount of CO2 the concrete consumes is likely to be insignificant in the bigger picture, but the real environmental advantage of the material lies in its longevity. Rahbar expects this kind of self-healing technology could extend a structures’ life from 20 to 80 years, reducing the need to produce and ship replacement concrete. The research was published on April 15 in the journal Applied Materials Today.
Rahbar emphasized:
Healing traditional concrete that’s already in use is critically beneficial, too, and will help reduce the need to produce and ship additional concrete, which has a huge environmental impact.
Watch the self-healing concrete in action in the video below.
