Self-Healing Concrete Nears Real-World Debut

Purdue University graduate students (from left) Paul Imbrock, Kambiz Raoufi and John Schlitter pour concrete for further tests of their "internally cured" mixture, which appears to extend and improve the life of concrete bridges and structures. The researchers assisted with installation of an internally cured bridge in 2010, and the state plans to use the mix in four new bridges this year. Credit: Purdue University photo/Andy Hancock

Concrete mixtures with "healing" properties are moving closer to the marketplace on two continents, as researchers in Indiana and Belgium are developing technology to strengthen structures against water damage and cracking.

At Indiana's Purdue University, researchers have developed a new high-performance concrete that relies on "internal curing" to extend the lifespan and maintenance needs of bridges. Internal curing replaces some of the sand in the mixture with small porous stones, which create pockets that enhance the reaction between the water and cement.

Purdue professor Jason Weiss says testing shows the internally cured concrete is less prone to cracking and damage caused by deicing salt. The university worked with the Indiana Department of Transportation to develop specifications for the new material to be used on four bridges this year, and INDOT expects the new concrete to be used more widely in the future.

On the other side of the Atlantic, sustainability consulting firm Cowi is field-testing new technology that uses bacteria to mitigate water and chemical damage to concrete structures by mixing limestone-producing bacteria with the concrete.

Led by the University of Ghent in Belgium, the "Healcon" project adds endolithic bacteria, which can live inside stone, to the concrete mix. The project's goal is to extend the life of concrete structures, marine structures in particular. Similar research is also being conducted in the Netherlands.

Cowi will be leading the project's end-user board and will perform life cycle cost analysis to make sure the relevant industries get maximum benefit from the project.

"It is much like the bones of the human body, really, where broken bones heal themselves over time," said Carola Edvardsen, Cowi's concrete specialist who began researching self-healing concrete two decades ago. "As the water seeps into the concrete, the bacteria will activate and start producing limestone, which will mend the cracks before they become a threat to the structure," she said.

Edvardsen said that the project is expected to cut maintenance costs by up to 2 percent, which could save the equivalent of more than $130 million annually in the EU alone.

"The main unknown is how long the bacteria can survive inside the concrete, but all data points in the same direction – this is going to work."