Self-Healing Concrete Repairs Cracks

Outdoor trials await a novel new type of self-healing concrete developed by Dutch researchers working at Delft Technical University.

The self-repairing concrete was conceived by Doctor Henk Jonkers - a microbiologist - and Eric Schlangen - a concrete technology expert. If the trials have a positive outcome, this technology -which holds much promise for the construction industry - could be commercialised from 2014 onwards.

The concrete's remarkable properties are the result of in-built bacteria which, when rainwater's introduced, produce limestone.

Concrete is used in the construction industry more than any other material but, when placed under pressure, it can crack. Serious concrete cracks can compromise structural integrity so, typically, more steel than needed is used to supply reinforcement but this adds extra cost. The cracks can always be repaired but, in certain situations, that's an extremely tricky process.

Self-Repairing Concrete

The self-repairing concrete development programme, therefore, represents a potentially valuable solution for constructors the world-over.

The concrete's made from a mix that includes bacterial spores and the nutrients needed to sustain them. These lie, inactive, in the concrete until rainwater arrives on the scene. It's this rainwater that triggers the microbes' growth and the limestone that's then produced effectively heals over the cracks that have developed.

In a laboratory environment, Doctor Jenkers and his team have used this process to repair cracks up to half-a-millimetre wide. Now, they're preparing to put the material through its paces outdoors, once it's been established that the healing material has enough strength.

Concrete Heals Cracks

Thereafter, the concrete that heals cracks will need to be studied for at least two years, to ensure it can perform as well in a real-life environment as in the lab. Only if these studies are positive could it start to be manufactured and distributed en masse so, clearly, its commercial advent is still many months away.

Even so, it's a product with the potential to dramatically lower the overall cost of constructing new structures in the long-term.

"In the lab we have been able to show healing of cracks with a width of 0.5mm - two to three times higher than the norms state", Dr Jonkers told the BBC. "Now we are upscaling. We have to produce the self-healing agent in huge quantities and we are starting to do outdoor tests, looking at different constructions, different types of concrete to see if this concept really works in practice."

Image courtesy Dr Henk Jonkers/Delft Technical University