Self repairing concrete block

‘Living concrete’ can self-repair

Researchers in Colorado are hoping to revolutionise construction with living building materials created using bacteria. The innovative method presented in the journal Matter, combines sand and bacteria to build a living, load-bearing material.

The scientists from the College of Engineering and Applied Science at the University of Colorado Boulder hope that their ‘living concrete’ could eventually help to reduce the environmental impact of construction, the production of which is responsible for six percent of CO2 emissions worldwide.

“Concrete is the second-most consumed material on earth after water,” lead researcher Wil Srubar told New Scientist. 

To make the new ‘living concrete’ Srubar and his colleagues combined a photosynthetic cyanobacteria with gelatine, sand and nutrients in a liquid mixture. Adding heat and sunlight then allowed the bacteria to produce calcium carbonate crystals around the sand particles, in a process similar to the formation of seashells.

When cooled, the mixture solidifies into a gel form, which is then dehydrated to further toughen it, with the whole process taking only a few hours. 

Furthermore, as the hydrogel-sand brick is alive it can also reproduce, in the phase before it becomes structural, with the addition of some extra sand, hydrogel and nutrients.

Srubar and his team have demonstrated that one parent brick can reproduce up to eight bricks after three generations – something he says opens up the possibility of moving from a linear manufacturing approach to an exponential one in the future.

In tests, the material was shown to hold up to compression as well as a low-grade traditional concrete, and the presence of the cynobacteria improved its resistance to fracture by more than 15%. 

However, the mechanical properties of this new ‘concrete’ are more similar to mortar, a weaker material, says Srubar, who admits the new material isn’t quite as strong as regular bricks. 

But with the potential for a greener form of building material a positive move forward for the industry, his team is now in talks with the US Department of Defense to scale up production of the ‘living concrete’ and pilot its use in construction.

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