Materials

Self-healing concrete eats CO2 to fill its own cracks in 24 hours

Self-healing concrete eats CO2...
Prof. Rahbar (R) and his team have developed self-healing concrete using an enzyme found in red blood cells
Prof. Rahbar (R) and his team have developed self-healing concrete using an enzyme found in red blood cells
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Prof. Rahbar (R) and his team have developed self-healing concrete using an enzyme found in red blood cells
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Prof. Rahbar (R) and his team have developed self-healing concrete using an enzyme found in red blood cells
Samples of the self-healing concrete
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Samples of the self-healing concrete

Concrete has a massive carbon footprint, so technologies that boost its performance and enable it to last longer could have profound benefits for the environment. This has led to the development of self-healing concrete that can repair its own cracks, and scientists have now demonstrated an exciting new form of this that makes use of an enzyme found in human blood.

Tiny cracks that form in concrete mightn't pose an immediate problem to the structural integrity of a construction, but as water gets in and the rupture spreads it can greatly compromise its strength. The idea with self-healing concrete is to intervene in this process while the cracks are still tiny, sealing up the material to prevent not just a catastrophic collapse, but expensive maintenance or a complete replacement of the structure.

This field of research has turned up all kinds of interesting potential solutions over the years. We've seen versions that pack their own sodium silicate healing agents, ones that feature bacteria that produce special glue to knit together these cracks, and others that fill up the gaps with fungus. While promising, scientists at the Worcester Polytechnic Institute have conjured up what they believe is a cheaper and even more efficient solution.

The team sought inspiration from the human body; more specifically, from the way an enzyme in red blood cells called carbonic anhydrase (CA) is able to quickly transfer CO2 from the cells into the bloodstream.

“We looked to nature to find what triggers the fastest CO2 transfer, and that’s the CA enzyme,” says study author Nima Rahbar. “Since enzymes in our bodies react amazingly quickly, they can be used as an efficient mechanism to repair and strengthen concrete structures.”

The team put the CA enzyme to use by adding it to concrete powder before the material is mixed and poured. When a small crack forms in the concrete, the enzyme interacts with CO2 in the air to produce calcium carbonate crystals, which mimic the characteristics of concrete and promptly fill in the crack.

Samples of the self-healing concrete
Samples of the self-healing concrete

Through their testing, the scientists demonstrated their doped concrete can repair its own millimeter-scale cracks within 24 hours. The team says this is a marked improvement on some previous technologies that have used bacteria to self-heal, which are more expensive and can take up to a month to heal even far smaller cracks.

While the amount of CO2 the concrete gobbles up is likely to be negligible in the grand scheme of things, the real environmental potential of the material lies in its potential longevity. Rahbar predicts that this type of self-healing technology could extend the life of a structure from 20 years to 80 years, which reduces the need to produce replacement concrete in what is a notoriously carbon-intensive process.

“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,” says Rahbar.

The research was published in the journal Applied Materials Today, and the video below shows the self-healing concrete in action.

Self-Healing Concrete in Action

Source: Worcester Polytechnic Institute

10 comments
10 comments
Worzel
This process may fill the gap, but does it BOND the gap?
Fish
Well, we are in effect creating manmade carbon sinks, are we not?
Aross
No mention of how they would produce or harvest the enzyme. This poses the question, how many humans does it take to repair a concrete bridge?
claudio
so, it needs to be submersed in water, for the process to work?
Catweazle
"extend the life of a structure from 20 years to 80 years"
There are Roman concrete structures 2,000 years old.
This is progress?
Signguy
HEMPCRETE!!! WORKS BETTER THAN ANY OTHER CONCRETE!
paul314
"...this type of self-healing technology could extend the life of a structure from 20 years to 80 years" ? There are plenty of concrete structures already with lives way longer than 20 years. 50 is pretty common, 100 or more is not unknown. Sure, some structures die from corrosion, but a lot more just get torn down and replaced with something else because they're not useful any more. Maybe architects will design buildings that can be repurposed easily when their original role is done?
mikewax
it looks to me like the advantage comes in preventing rainwater from penetrating the interior
rbhall52
I think the way to heal concrete in this article is a great idea, but that's not because our environment needs less carbon in it, such as CO2. We need more CO2, as the plants need it to grow and we need the plants to replenish our oxygen so that we can live. More CO2 also means better crops for food. This is biology 101.
MrD
Is this how the Borg started? Im pretty sure this is one of the steps of how they started! Are we really the Borg?