NPCA staff report
Concrete is among the most durable construction materials in the world. And as technology advances, researchers have found ways to further improve its durability by creating a concrete mixture that can heal itself.
There are many self-healing concrete technologies in development involving polymers, bacteria and other materials. Here is a look at a few.
Dr. Hendrik Jonkers of Delft Technical University in the Netherlands and his team have developed a bacteria that produces calcium carbonate when it comes into contact with air and moisture, for example, as the result of cracking. Incorporated into concrete mix, the bacteria fills the crack and “heals” the concrete. The product is sold both as an additive for fresh concrete and as a repair mortar for existing concrete.
Researchers at Ghent University in Belgium also have developed a self-healing concrete using bacteria embedded in super absorbent polymers or hydrogels. When a crack occurs, the hydrogels swell as they become exposed to humidity. This swelling reaction partially seals the crack and prevents potentially harmful substances from intruding. After swelling, particles desorb the fluid and provide it to the surrounding concrete matrix for internal curing, furthering the cement hydration and precipitation of calcium carbonate, which closes the crack completely.
At the University of Wuhan in China, researchers developed a self-healing concrete technology using encapsulated polymers. The polymers release when the encapsulation media reacts with air and moisture, which provide a material to seal the crack. Other healing or crack closure systems are activated by electrical current.
Many other universities are working on similar technology. Some field trials are under way, including one in Wales, where concrete retaining walls were installed with different combinations of self-healing technologies.
Concrete has a certain level of inherent self-healing ability as cement grains within the concrete matrix can react with moisture years after the concrete is poured, contributing to concrete’s strength, density and durability. Advancements in self-healing technologies further enhance concrete’s inherent self-healing ability, which could lead to making the best construction material even better.