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Friday, 12 May 2017 01:00

Using bacteria to make self-healing cement

Written by  TheStructuralEngineer.info

It is a common phenomenon for the traditional concrete to crack, requiring maintenance and reparations before reinforcement starts to corrode. Luckily, it seems that Delft University microbiology professor Henk Jonkers has found the solution to this problem. Inspired by nature, he developed ‘Bio-concrete’, a new type of material that brings together biology and civil engineering and could save billions in construction costs by improving the lifespan of buildings, bridges and roads. "It is combining nature with construction materials. Nature is supplying us a lot of functionality for free - in this case, limestone-producing bacteria’’, says the professor. 

‘Bio-concrete’ is infused with limestone-producing bacteria in capsule form, along with calcium lactate. The bacteria that Jonkers used, either Bacillus pseudofirmus or Sporosarcina pasteurii, thrive in alkaline conditions and are found naturally in highly alkaline lakes near volcanoes. Being mixed with concrete and distributed evenly throughout it, they can lay there in a dormant state for up to 200 years; only when the concrete cracks, air and moisture awaken the bacteria which use the calcium lactate as a food source and start to produce limestone, sealing off the cracks in 3 weeks’ time. The technology, currently able to seal cracks of any length but only up to 0.8 mm wide, was a finalist for the European Inventor Award 2015, an initiative of the European Patent Office (EPO).

Limitations

Currently the cost of this new technology is still considered prohibitive, as it is twice the cost of regular concrete manufacture (70-80 € / m3), making it only viable for projects where leakage and corrosion are particularly problematic, such as underground and underwater structures. The price of the calcium lactate nutrient for the bacteria is part of the problem, but Jonkers and his team are testing a sugar-based alternative instead that is expected to decrease the total cost, making ‘Bio-Concrete’ a sustainable prevention method.

Testing the new concrete

The world’s first structure where ‘Bio-concrete’ has been used is a lakeside lifeguard station in the Netherlands. Built in 2011 and subject to highly varied sunlight and weather conditions, the prototype has remained watertight since its construction.

 

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A slab of bio-concrete has just cracked

 

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The crack after 28 days

 

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The crack after 56 days

Photos source: CNN

 

 

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