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Concrete infused with live bacteria that can knit their own repairs into the material is advancing in development under scientists in the Netherlands.
The new technology employs calcite-precipitating bacteria in the concrete mixture, creating what the researchers call a self-healing version of the world's most commonly used building material.
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Sean Mack / Wikimedia Commons |
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The team is testing the concrete outdoors and in different constructions and types of concrete. This is Scotland's novel Falkirk Wheel boat lift.
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The scientists at Delft University of Technology’s Center for Materials say the technology makes it possible to produce concrete that repairs itself, thereby reducing maintenance costs and improving the safety of concrete structures.
Testing Underway
While they are still ironing out details on how to create the right conditions for the bacteria to thrive, the scientists say the “bio-concrete” could eventually transform how structures are made.
The team is also conducting outdoor tests, looking at different constructions and types of concrete to see how the concept works in practice, according to the university.
The project has been underway since 2005.
Living Concrete
The current issues are the care, feeding and survivability of the bacteria, the team says. As the pH value of concrete is very high, only so-called alkaliphilic bacteria are able to survive in the material.
“We have mixed several of these bacteria into a cement paste and, after a month, found the spores of three particular bacteria were still viable,” the scientists report.
Producing microscopic food that is durable enough to survive mixing and able to feed the bacterium is a significant obstacle in the process, the team says.
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Delft University |
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"Bio-concrete" embedded with bacteria may mean an end to costly concrete repairs by healing itself, researchers in the Netherlands say.
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“Our research focuses on creating the right conditions for the bacteria to produce as much calcite as possible and on optimizing the distribution of food for the bacteria,” researchers say.
The team is also looking at the self-healing ability of bacterial concrete and how this is affected by the various deterioration mechanisms involved, such as sulfate attacks or temperature fluctuations.
The research is conducted in a microlab where fracture testing equipment and numerical tools for structure information and fracture modeling are accessible.
Crack Prevention
The goal of the research is to overcome concrete's Achilles' heel: cracking.
“Although concrete is the world’s most used building material, it has a serious flaw: It can easily crack when under tension,” the researchers said.
“If these cracks become too large, they will lead to corrosion of the steel reinforcement, which not only results in an unattractive appearance but also jeopardizes the structure’s mechanical qualities.”
Crack prevention is why engineers often use a larger-than-necessary amount of steel reinforcement within a concrete structure—to prevent cracks from becoming too large, the researchers noted.
“The extra steel has no structural use and is an expensive solution as steel prices are high,” they said.
Cracks can be repaired, but this can be extremely difficult in underground or liquid-retaining structures.
Practical Uses
The researchers say bacteria-infused concrete may lead to substantial savings, especially in steel-reinforced concrete.
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Rehman / Wikimedia Commons |
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The world's largest power station in installed capacity, China's Three Gorges Dam used 27.2 million cubic meters of concrete—mainly for the wall, which rises 594 feet above its rock base. Researchers say stronger concrete would mean less steel in structures.
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“It will also mean durability issues can be tackled in a new and more economical way when designing concrete structures,” the team said in a statement.
The technology is also promising for constructing underground hazardous-waste retainers, as no humans would have to go near the structure to repair cracks, the team noted.
“For residential buildings, however, it does seem the traditional repairing of cracks will remain the most economically attractive solution for now,” they said.
The researchers are collaborating with the South Dakota School of Mines & Technology in Rapid City, SD, and others on the project.
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