Invention: Self-healing concrete containing bacteria
(Hendrik Jonkers, Delft University of Technology)
As solid and reliable as concrete structures may seem, they share one common enemy: tension. Over time, concrete will crack and deteriorate. 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.
When Hendrik Jonkers was looking for a way to improve the strength and longevity of concrete, he didn’t turn to the steel or stone techniques refined by countless engineers, but instead to an unlikely source for inspiration: the human body.
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 such as Bacillus pseudofirmus and related species, already exist in highly alkaline lakes near volcanoes and seemed tailor-made for the job. They are able to lie dormant for up to 200 years and only begin important repair work only after cracks appear and it comes into contact with water.
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. HealCON, an EU FP-7 funded project, estimates the annual maintenance cost for bridges, tunnels and earth-retaining walls in the EU member countries at up to € 6 billion.
Stress under pressure and a high price tag aren’t the only problems with concrete. Anywhere from 7 to 12% of the world’s annual CO2 emissions are related to the production of the building material.
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. With the current method, the production cost is still twice the cost of regular concrete manufacture (€ 80/m3).
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 (e.g. between € 85/m³ and €100/m3), 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, and bacteria will act as slumbering guardians that protect bridges, roads, tunnels and other concrete structures over a 200-year lifespan, only waking up when they’re needed.