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Are self-healing concrete buildings in our future?

We know that concrete deteriorates with age. Buildings, bridges, tunnels, dams and other concrete structures can be prone to cracking.

The cracking might be due to shrinkage as the concrete dries, movement beneath the structure, or repeated freezing and thawing.

Aside from these issues, the steel bars used to reinforce concrete can corrode over time. Even tiny cracks allow water and oxygen to penetrate and then to corrode the steel.

Repairing and maintaining concrete can be expensive, and require a large amount of labour.

So Congrui Jin, Assistant Professor of Mechanical Engineering at Binghamton University, State University of New York, has been looking at how to “heal” concrete cracks without any human intervention.

The inspiration for this idea came from the remarkable ability of the human body to heal itself. Our bones knit back together, cuts heal and bruises vanish.

And this all happens as we take on nutrients, which the body uses to produce substances that heal damaged tissues.

Jin wondered if there was a way to replicate this in concrete and, alongside colleagues at the university, found the perfect candidate: a fungus called Trichoderma reesei.

The team trialled 20 different species of fungi before settling upon this one. It was important to find fungi that could survive a wide pH range, from near neutral to very alkaline conditions, as calcium hydroxide from concrete, dissolved in water, creates an alkaline environment.

The plan with this technique is that when building a new concrete structure, fungal spores and nutrients will be included, and when cracking occurs and water seeps in, the dormant spores will germinate.

As the spores grow, they will promote precipitation of calcium carbonate crystals – mineral deposits that can fill in the cracks. Aside from its healing properties, T. reesei is non-pathogenic, eco-friendly, and poses no known risk to human health.

This biological repair technique isn’t fully understood yet, and research is only in the initial stages, but self-healing concrete could become a cost-effective solution to concrete deterioration in the future.

At Super Structure Associates, we are keen to embrace new techniques and new developments in our industry. If you have a project that requires a structural engineer, please do get in touch with me or one of my team.

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