Broken concrete, like a broken heart on Valentine’s Day, is not uncommon and difficult to mend, as it requires much labour and investment. However, researchers at Binghamton University and Rutgers University are working on a solution (for the concrete, not the broken hearts). They discovered that adding fungus to the mix could cause the concrete to heal itself.

Concrete expands and shrinks during everyday use, because of heat and moisture, which causes the concrete to crack. Microcracks can allow water and oxygen to infiltrate, which, in case of reinforced concrete, can cause the steel to corrode.

Rather than continuing to repair the concrete, the researchers started looking for a way to create a concrete that can heal itself, like a living organism. They found an unusual candidate for the job: a fungus called Trichoderma reesei.

As the calcium hydroxide from concrete dissolves in water, the pH of the fungal growth increases from a close-to-neutral value to one that is very alkaline. Of all the fungi tested. Only T. reesei survived that environment. Despite the pH increase, the spores keeping germinating to mycelium. T. reesei is eco-friendly and nonpathogenic, posing no known risk to human health. Despite its widespread presence in tropical soils, there are no reports of adverse effects in aquatic or terrestrial plants or animals.

The researchers propose to include fungal spores and nutrients into the concrete mix. When cracks appear and water enters, the fungal spores will start to grow, working as a catalyst to promote the precipitation of calcium carbonate crystals. These minerals then fill in the cracks. This process can repeat itself indefinitely.

The research is still in the initial stage and there’s a long way to go to make self-healing concrete practical and cost-effective, but perhaps we’ll see self-healing building soon enough. Now we only need something to mend those hearts.

Photos: Congrui Jin / Pxhere