Bacterial Builders Are the Key to Concrete Alternatives

The living world is being used to find alternatives to concrete. Many different animals, such as tortoises, turtles and oysters, produce hardened structural materials of their own, but one of the most interesting sources of hard materials comes from certainbacteria that produce calcite, a form of calcium carbonate that makes up limestone.

25 billion tons of concrete is produced every year, making it the most widely consumed material. It lasts decades longer than other building materials and it doesn't rot. The manufacturing of cement, the primary component of concrete, is the most energy intensive of all manufacturing industries, accounting for 8 percent of global carbon dioxide emissions.

As we look at the changes occurring to the Earth's climate, we must now consider the environmental costs of concrete production. Living construction materials such as calcite-producedbacteria, which have a lower carbon footprint, could be useful for a variety of purposes.

On the Mend.

It is possible to repair cracks in concrete with the help of the bacteria. The brittle nature of concrete makes it susceptible to cracking. Traditional repair methods use expensive chemicals that require hands-on work. The dispersions of abacteria called Bacillus halodurans can be sprayed into the cracks.

The technology showed that the calcite that was produced by the bacteria was able to penetrate the entire crack depth to form a permanent seal. A liquid repair system has recently appeared on the market.

Concrete that heals itself is being made with the use of calcite-producedbacteria. The Dutch scientists encapsulated the Bacillusbacteria in a plastic container with calcium lactate as a food source. The concrete mix was then added to the capsules. When a crack appeared in the concrete, the rain entered and dissolved the plastic, allowing thebacteria to metabolize and produce healing calcite.

Henk Jonkers is a researcher at the Delft University of Technology in the Netherlands. Nature is giving us a lot of function for free. If we can implement it in materials, we can really benefit from it, so I think it is a nice example of tying nature and the built environment into one new concept.

Growing up.

Scientists at the University of Colorado Boulder have been usingbacteria to make a building block that doesn't contain cement at all. The low-carbon construction material was made by pouring a mixture of sand, gelatin, calcium nutrients and a photosynthetic cyanobacterium into a mold. The scaffold formed when the set was made. A solid block that is roughly as strong as a cement-based block can be created by depositing calcium carbonate.

There is one key difference. The strength of traditional cement-like materials is measured after 28 days. Blocks made by the bacterium get their full strength in seven days.

It is possible to use this method to grow structural materials in hostile environments. sacks of the constituents could be distributed in a dehydrated form because there is little material needed. A system like this might be useful for temporary civil and military structures.

There are advantages to keeping the blocks wet so that thebacteria can perform other useful functions. In the event of an earthquake, this building material could be used to reverse structural damage. It is possible to sense and respond to toxins in the air or glow in the dark.

Wil Srubar, an assistant professor of engineering at the University of Colorado Boulder, was involved in the research and said that biological materials are no longer alive. We are asking, why can't we keep them alive and have that biology do something beneficial too?