Self-healing concrete containing bacteria
An invention by Delft University microbiologist Hendrik Jonkers offers an innovative approach to creating more stable concrete by adding limestone-producing bacteria to the mix. This self-healing bioconcrete aims to provide a cheap and sustainable solution, markedly improving the lifespan of buildings, bridges and roads.
Thinking about the how bones in the human body are healed naturally through mineralisation from osteoblast cells, Jonkers set about creating a similar self-regeneration technique for our most widely used construction material.
The solution that he landed upon employs a limestone-producing bacteria to close up gaps in concrete. The robust, naturally occurring bacteria ̶ either Bacillus pseudofirmus or Sporosarcina pasteurii, already exist in highly alkaline lakes near volcanoes and seemed tailor-made for the job. The bacteria, along with nitrogen, phosphorus and a calcium-based nutrient known as calcium lactate, are added to the ingredients of the concrete when it is being mixed. These agents can lie dormant within the concrete for up to two centuries.
When a crack emerges in the concrete, admitting air and moisture, the bacteria awaken and start to feed on the calcium lactate. During the process, they also consume oxygen, and the soluble calcium lactate is converted to insoluble limestone. The limestone solidifies in the cracks, sealing them again.
The technology can seal cracks up to any length provided they have a width of no more than 0.8 millimeters.
The potential for the patented technology is impressive. Because around 70% of Europe’s infrastructure is comprised of concrete, maintenance is an extremely costly affair.
Jonkers’ self-healing bioconcrete is expected to hit the market in 2015. The main hurdle yet to be overcome is the material’s price, which depends on the application method. A large part of the cost is the expensive calcium lactate nutrient for the bacteria, but Jonkers and his team are well underway to creating a sugar-based nutrient, which would reduce the cost to a level far closer to that for regular concrete, making it a viable additive and sustainable prevention method.
If Jonkers and his team succeed in overcoming the pricing obstacle, bioconcrete will truly be the concrete of the future.
