For self-healing concrete, just add bacteria and food

[Studeo]

Like living bone, concrete could soon be healing its own hairline fractures – with bacteria in the role of osteoblast cells. Worked into the concrete from the beginning, these water-activated bacteria would munch food provided in the mix to patch up cracks and small holes.
Concrete reinforced with steel forms the skeleton of many buildings and bridges. But any cracks in its gritty exterior make it vulnerable: "Water is the culprit for concrete because it enters the cracks and it brings aggressive chemicals with it," says Henk Jonkers of Delft University of Technology in Delft, the Netherlands. These chemicals degrade both concrete and steel.
Locating and patching cracks in old concrete is a time-consuming business, but rebuilding concrete structures is expensive. Jonkers thinks the solution is to fight nature with nature: he suggests combating water degradation by packing the concrete with bacteria that use water and calcium lactate "food" to make calcite, a natural cement.
Surviving soda
Unfortunately, most organisms keel over in a pH above 10, which is typical of concrete. To find bacteria that are happy in such an alkaline environment, Jonkers and his colleagues looked to soda lakes in Russia and Egypt where the pH of the water is naturally high – and found that some strains of Bacillus thrived there.
Moreover, the bacteria can take on a dormant spore state for long periods – up to 50 years, according to Jonkers – without food or water. He compares them to seeds waiting for water to germinate.
To keep the spores from activating in the wet concrete mix, and to keep them and their calcium lactate food from affecting the quality of the concrete, Jonkers and his colleagues first set both into ceramic pellets 2 to 4 millimetres wide and then added them to the concrete.
Only when tiny cracks form in the concrete – opening up the pellets – and water seeps inside will the bacteria activate and begin to consume the food that has also been freed. As they feed, they combine the calcium with oxygen and carbon dioxide to form calcite – essentially pure limestone.
Surface seal
Brajadulal Chattopadhyay of Jadavpur University in Kolkata, India, says the work is "very interesting" and will "help to find a path for the development of real self-healing concrete in the near future". But he doesn't know how the bacteria can produce calcite deep in concrete, where they would be starved of the oxygen they need to metabolise the calcium lactate.
Jonkers argues that it is not necessary to form calcite at such depths: simply sealing off the crack with calcite near the surface is enough to prevent water invading deep enough into the concrete to weaken the structure. "If there's no water, there's not really a fear of damage," he says.
There's also no fear of these bacteria turning into a health threat or ecological problem, he says – they die in the relatively pH neutral environments preferred by humans.
Jonkers's team now aims to reduce the material's cost and make sure its strength remains comparable to concrete currently on the market.
Jonkers presented his work at the EU-US Frontiers of Engineering symposium in Cambridge, UK, today.

http://www.newscientist.com/article/...-and-food.html

[Ross]

Excellent Studeo,

I sent this to my Chemistry friend who happens to like concrete....


Regards

Ross

[Studeo]

Your welcome Ross. Very interesting info to be sure. Amazing what the boffins come up with.

[Fredkc]

Brajadulal Chattopadhyay of Jadavpur University in Kolkata, India, says the work is "very interesting" and will "help to find a path for the development of real self-healing concrete in the near future".

OMG!!! What incredible news!!
I have long held that the only legitimate purpose for government, is filling pot holes!
And that they are even incapable of that, without rampant corruption.

Now comes news that we may actually construct "pot hole free" roads?
Both Sliced Bread, AND the wheel pale in comparison.

Fred

[Ross]

Thank god we have you here Fred...