The concrete industry has been in the news a lot lately: 3D concrete printing, concrete’s massive carbon footprint and new, innovative approaches to mitigate that environmental impact, America’s D+ grade in the recently released Infrastructure Report Card. Crumbling concrete in the U.S. and around the world is going to require repairing and rebuilding, soon. The good news is that public universities, entrepreneurs and scientists are exploring new ways to address this global problem.

In the U.S. and Canada, most bridges, roads, dams and other structures are made of reinforced concrete. Corrosion happens when water and oxygen penetrate through small cracks in the concrete. When the cracks grow larger, exposed metal reinforcement (rebar) is attacked, and rusts. Corrosion is responsible for up to 90% of damage to concrete structures; repairing corroded concrete is expensive and complex. 

Bio-concrete

Inspired by the human body’s ability to heal itself, bio-concrete was first developed 10 years ago by Hendrik Jonkers at Delft University of Technology in the Netherlands. He discovered that adding limestone-producing bacteria and nutrients to concrete mix brought it to life, increasing the concrete’s ability to stay strong over time. Jonkers chose bacillus bacteria for the job, because they thrive in alkaline conditions and produce spores that can survive for decades without food or oxygen.

Congrui Jin at Binghamton University, State University of New York, Ning Zhang at Rutgers University in New Jersey, and a few friends have recently discovered that adding a form of fungus called Trichoderma reesei – a sort of mushroom - to concrete can create “self-healing” concrete. The fungus spores lie dormant until cracks in the concrete allow water to get in; the water activates the spores to germinate, filling in the cracks and causing calcium carbonate – which has a structure similar to concrete - to form. The research suggests that this exciting new approach could permanently heal the concrete.

Whereas bacteria introduced into the concrete can create nitrogen products including ammonia, Trichoderma reesei doesn’t produce harmful by-products and is deemed more environmentally friendly. The fungus is benign to humans, low-cost, removes CO2 , and is pollution-free. Further research is needed to determine how to ensure the spores will survive when added to mixed concrete.

Concrete is the world’s most widely used construction material. Bio-concrete as a method to repair our crumbling concrete infrastructure holds great promise. It’s good to know that the best and brightest scientists are working on solutions to address this global challenge.