Scientists Develop Self-Repairing Concrete
Scientists at Delft University of Technology in the Netherlands have developed a self-repairing concrete. This new type of concrete uses bacteria to help repair fractures before they can spread. The new formulation may someday eliminate the time-consuming inspection and patching currently required to maintain safe concrete structures.
Spearheaded by Dr. Henk Jonkers, the new concept in making concrete is based on the way human bones can self-heal hairline fractures. Currently, when a concrete structure cracks, water then seeps into the gaps and causes chemical deterioration that degrades both the concrete and the steel commonly used to reinforce it.
Jonkers theorized that bacteria found in nature could be used to convert the unwanted water and calcium lactate into a natural cement called calcite. The challenge was to find microorganisms that could live in the high pH environment, above 10, that concrete provides. The team of scientists researched and found soda lakes in Egypt and Russia with naturally high pH water that harbored certain stains of Bacillus. Additionally, the scientists found that these bacteria are able to remain dormant for up to 50 years without water or food, like seeds awaiting the right conditions for germination. The bacteria remain inactive until water seeps inside tiny cracks in the concrete.
The scientists packed the bacteria and their calcium lactate nutrients into ceramic pellets and added them to wet concrete mix. Once activated, the bacteria consumed the calcium lactate and combined it with oxygen and carbon dioxide to form the limestone calcite.
If the new method works, sealing cracks close to the surface with calcite could prevent water from invading deeply enough to weaken the concrete structure. More testing will need to be done to see if the new formulation will work under real-life conditions.