Author Nicholas DeRenzo
The old rhyme “Step on a crack, break your mother’s back” may soon be seen as quaintly outdated. That’s because, thanks to research at the Delft University of Technology in the Netherlands, the very concept of a sidewalk crack could become a thing of the past. Cement is the world’s most widely used building material, but unavoidable cracks lead to leaks that weaken steel support systems, causing serious damage or even collapse. To solve this costly, potentially disastrous issue, microbiologist Henk Jonkers has invented a “bioconcrete” that boasts the nearly superheroic power of healing its own cracks, much as skin self-heals after a cut. While this innovation may sound sci-fi, the concept actually draws on the least high-tech source imaginable: The cement is infused with a “healing agent” made of calcium lactate (found in baking powder) and a strain of bacteria that is literally found under a rock. Here’s how Jonkers is taking a crack at solving one of construction’s most persistent problems.
1. Cement is a highly alkaline substance that is an inhospitable home for most organisms. Researchers searched far and wide for a bacterium that could handle the job, settling on the genus Bacillus, which can be found inside rocks and near active volcanoes. The bacteria, which can remain dormant for up to 200 years, are placed inside biodegradable capsules alongside calcium lactate and then mixed into cement, spread throughout like blueberries in a muffin.
2. Once a crack forms in the cement and water reaches the capsules, the microbes spring into action, awakening from their dormancy, multiplying and then eating the calcium lactate. During the “digestion” process, the calcium lactate is transformed into calcite, or pure limestone, which seals the crack like a scab.
3. In addition to being used directly in construction, Jonkers’ healing agent comes in a sprayable version that can be applied to already-formed cracks, much like a liquid bandage. The spray is slated to be released this year, while bioconcrete is expected to first be used in construction projects in 2016.