It’s a generally accepted truth that the “body can heal itself”. But have you ever heard that, of all things, concrete can be self-healing and fix its own cracks?
Well now, you have.
The new “self-healing” concrete was created by Congrui Jin, Guangwen Zhou and David Davies from New York’s Binghamton University, along with Ning Zhang from Rutgers University.
“This idea was originally inspired by the miraculous ability of the human body to heal itself of cuts, bruises and broken bones,” said Jin. “For the damaged skins and tissues, the host will take in nutrients that can produce new substitutes to heal the damaged parts.”
It incorporates spores of the fungus Trichoderma reesei, along with nutrients, that are placed within the concrete matrix as it’s being mixed. When this fungus is mixed with concrete, it originally lies dormant — until the first crack appears.
“The fungal spores, together with nutrients, will be placed into the concrete matrix during the mixing process. When cracking occurs, water and oxygen will find their way in. With enough water and oxygen, the dormant fungal spores will germinate, grow and precipitate calcium carbonate to heal the cracks,” explained Jin.
“When the cracks are completely filled and ultimately no more water or oxygen can enter inside, the fungi will again form spores. As the environmental conditions become favorable in later stages, the spores could be wakened again.”
Once the concrete has hardened, the spores remain dormant until the first micro-cracks appear. When they do, water and oxygen find their way in. This causes the spores to germinate, grow, and precipitate calcium carbonate, which in turn seals the cracks.
Why is concrete healing itself such a big deal? Well, for one thing, it could help save America’s crumbling infrastructure.
Jin, assistant professor of mechanical engineering at Binghamton University, said the problem stems from the smallest of cracks. “Without proper treatment, cracks tend to progress further and eventually require costly repair,” said Jin. “If micro-cracks expand and reach the steel reinforcement, not only the concrete will be attacked, but also the reinforcement will be corroded, as it is exposed to water, oxygen, possibly CO2 and chlorides, leading to structural failure”.
“These cracks can cause huge and sometimes unseen problems for infrastructure. One potentially critical example is the case of nuclear power plants that may use concrete for radiation shielding. While remaking a structure would replace the aging concrete, this would only be a short-term fix until more cracks again spring up.”
Jin wanted to see if there was a way to permanently fix the concrete and the use of fungus mixing with concrete is the promising start to his idea.
The research is still in the fairly early stages, with the biggest issue being the survivability of the fungus within the harsh environment of concrete. However, Jin is hopeful that with further adjustments the Trichoderma reesei will be able to effectively fill the cracks.