Assistant professor Congrui Jin (centre) with two Binghamton University graduate students from the Mechanical Engineering Department. Image: Jonathan Cohen.

US researchers have developed a self-healing concrete by adding an unusual ingredient into the mix – a fungus called Trichoderma reesei.

When mixed with concrete the fungus lays dormant until cracks appear.

“The fungal spores, together with nutrients, will be placed into the concrete matrix during the mixing process,” assistant professor of mechanical engineering at Binghamton University Congrui Jin said.

“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.

“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 favourable in later stages, the spores could be wakened again.”

Dr Jin said the idea for the concrete came from the ability of the human body to heal itself.

“For the damaged skins and tissues, the host will take in nutrients that can produce new substitutes to heal the damaged parts,” she said.

The findings of the research could help reduce costly infrastructure repair bills, and improve infrastructure safety.

“Without proper treatment, cracks tend to progress further and eventually require costly repair,” Dr Jin said.

“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.”

The “eco-friendly and nonpathogenic” Trichoderma reesei was selected from about 20 different species of fungi due to its higher ability to survive in the harsh environment of concrete. However Dr Jin said the research was still in its early stages with survivability of the fungus still a major issue.

“There are still significant challenges to bring an efficient self-healing product to the concrete market. In my opinion, further investigation in alternative microorganisms such as fungi and yeasts for the application of self-healing concrete becomes of great potential importance.”

Dr Jin’s research was conducted alongside professor Guangwen Zhou and associate professor David Davies from Binghamton University, and associate professor Ning Zhang from Rutgers University.

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