Researchers from New York’s Binghamton University have been looking into how to help concrete repair itself using a special kind of fungi.
While the 20th century brought with it some remarkable roads, bridges and architecture, many of those are now aging and in danger of falling apart.
They may be doomed, but thanks to new research led by assistant professor Congrui Jin of the State University of New York at Binghamton University, there may soon be hope for longer-lasting structures in the future.
What Jin considered is the first known formal look at the use of fungi to make self-healing concrete.
As many have noted in the past, one of the main reasons for the slow decay in the structural integrity of concrete structures is the small cracks that appear within it.
In examining that, Jin noted, “Without proper treatment, cracks tend to progress further and eventually require costly repair.” He added that if this problem is allowed to continue and “if micro-cracks expand and reach the steel reinforcement, not only will the concrete be attacked but also the reinforcement will be corroded, as it is exposed to water, oxygen, possibly CO2 and chlorides, leading to structural failure.”
That could spell major problems in any number of building applications.
The conventional approach to handling this is to inspect the structure, carve out the aging concrete and perhaps rebuild major parts of it. But that only postpones the eventual need to replace the whole thing. It also does not protect the construction against hidden decay in the areas that were not replaced.
Jin saw this and took a different approach to finding a way to fix the concrete in a more permanent way.
He took his inspiration from the way the human body is able to heal itself of everything from minor bruises and cuts to broken bones. Even more amazing, the body also often rebuilds itself to be even stronger after a problem than it might have been in the first place. Jin wondered if this might be possible with concrete.
Working alongside Rutgers University associate professor Ning Zhang, plus both professor Guangwen Zhou and associate professor David Davies of his own institution, Binghamton University, Jin searched for a solution.
What the team came up with was to mix a fungus called Trichoderma reesei with the concrete.
In the solution they explored, the fungus lay dormant until the first crack showed up in the finished structure. As Jin explained, “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.”
It turns out that when those cracks are completely filled, strengthening the concrete, the fungi go back into a dormant state again, forming spores but not doing much else. When further cracks appear, the cycle repeats.
It should be pointed out that this is still a very early stage research project, with much work still remaining to be done before any consideration can be made to convert this into a mass-manufacturable solution. One of the biggest challenges, Jin admits, is how to keep the fungi alive in the unforgiving and harsh environment of the finished concrete.
He and his team are continuing their research and hope to make further major strides on the commercial viability of the concept in the near future.