Bioconcrete Heals itself. Could this be the future of construction?
Concrete has been the one of the world’s most popular building material ever since the Romans built the pantheon from it over 2000 years ago. Since then, we have been looking for ways to make concrete more durable and last longer but regardless of how well it is mixed or reinforced all concrete eventually cracks. Under some conditions these cracks can lead to structural instability and eventual collapse, as they expose the concrete to water and the elements.
A group working at the Delft University of Technology in the Netherlands has developed bioconcrete to try and resolve the issue of cracks once and for all. This bioconcrete is a form of concrete specially created to self-heal when cracks form, meaning that cracks should seal themselves with minimal maintenance required from construction workers.
So, what is it?
Bioconcrete is mixed like normal concrete however, it has one additional ingredient, this being the ‘healing agent’. This agent doesn’t break down when the concrete is initially mixed, it only dissolves and becomes active if and when the concrete cracks and water gets in.
The agent takes the form of a specialist bacteria, suited to survival in the harsh and dry environment formed by concrete. The key for the researchers from the Netherlands was finding a bacteria that could survive a long time within the concrete, as often it will have to wait dormant for years before a crack forms and it is activated.
In the end, Professor Henk Jonkers, the key researcher decided to use bacillus bacteria as they thrive in the alkaline conditions of concrete and produce spores which can survive decades without food or oxygen, which was ideal. Jonkers then needed some form of sustenance for the bacteria so that they would activate and produce limestone to seal the crack. He made the decision to use calcium lactate as this wouldn’t weaken the concrete and other alternatives would have.
The bacteria and calcium lactate are set in capsules made of biodegradable plastic and then added to the wet concrete mix. When cracks eventually begin to form in the concrete, water will seep into them and enter the open capsules. The water causes the bacteria to germinate, multiply and feed on the lactate. In doing so they combine the calcium with carbonate ions to form calcite, or limestone, which closes up the cracks.
Click here for a short video on bioconcrete.
‘It is combining nature with construction materials. Nature is supplying us a lot of functionality for free, in this case, limestone producing bacteria.
If we can implement it in materials we can really benefit from it, so I think it’s a really nice example of tying nature and the built environments together in one new concept’
Professor Henk Jonkers, Delft University