A building with cracks in the wall? If it is up to Wil Srubar, that will soon be a thing of the past. In his lab he developed concrete containing live cyanobacteria that repair cracks by itself. And that is also good for the environment.
|Concrete made from bacteria for construction on mars.|
|Concrete stone made from bacteria.|
The concrete was developed by Srubar and his team from the Living Materials Laboratory of the University of Colorado in Boulder. 'We already use so many dead natural materials, such as wood. Why can't we let it live and take advantage of biology? "Srubar says.
|Concrete from bacteria for construction on mars.|
The production of the concrete starts, as always, with sand. Gelatin is then added to ensure that it contains sufficient moisture and nutrients. The final ingredient of the mixture is a substantial amount of cyanobacteria of the genus Synechococcus.
Among other things, the bacteria use carbon dioxide (CO2) to make calcium carbonate. Instead of producing CO2, this concrete actually absorbs CO2.
This is a major advance: the production of concrete annually accounts for 6 percent of the total CO2 emissions on earth. The calcium carbonate made by the bacteria reacts with the gelatin, which then binds the sand grains together and voilà: a concrete stone.
|Concrete from bacteria.|
Three generations of stones
The concrete is just as sturdy as normal concrete, but contains living materials.
This gives the stones not only the ability to repair themselves, but also to reproduce.
The bacterial colonies can grow exponentially, as long as sufficient sand and gelatin are added. This way new concrete bricks are created.
One 'mother stone' thus forms eight new stones within three generations. The researchers can turn this process on and off themselves by adjusting the temperature.
The bacteria are not active at low temperatures, but they do survive. They will reproduce at a higher temperature.
The newly made concrete bricks can have a nice punch. After 30 days, 9-14 percent of the bacteria are still alive.
For comparison: of bacteria that are added to normal concrete to repair it, only about 1 percent survives longer than a month.
|Concrete made from bacteria.|
Before you can buy the concrete in your local hardware store, there is still a lot to do. Only when the concrete is completely dry is it strong enough. This goes against the will of the bacteria: they prefer moisture more.
The bacteria can only survive if the humidity is high enough: above 50 percent. The researchers are now working on adjusting the DNA of the bacteria so that they can survive in drought.
Despite these minor problems, Srubar is positive. He predicts that we can do much more with this material in the future.
'This material is the basis for other innovative materials that are designed to interact with the environment. This is just the beginning, "says Srubar.
He predicts that concrete can be made that can detect and absorb toxins in the air. In addition, cyanobacteria can give light under certain circumstances, so that we can also produce luminous concrete.
Erik Schlangen, professor of experimental micromechanics at TU Delft, still has his doubts. "These bacteria probably produce limestone.
This limestone is much less solid than concrete. All claims made about the strength of concrete made by bacteria must be read with some caution, "he says.
Moreover, the storage of toxic substances does not seem like a good idea. 'We try to reuse as much as possible in construction. If there is poison in the concrete, the chain is contaminated, "says Schlangen. Recycling is then no longer possible.
Build on Mars
Srubar sees it as positive and believes that we can also use the concrete in areas with few raw materials. 'This concrete requires a lot of light for production and few other materials. This makes it suitable for the desert, for example, "says Srubar.
'In fact, we may also be able to take this to Mars. We are not going to drag bags of cement with it. I am very sure that when we go to Mars , we take biology with us. "
Schlangen has only one comment on this: "It seems rather premature to me, unless he has found more than enough water there ..."