When William McDonough and other pioneers of the sustainable architecture movement first envisioned the concept of living, breathing buildings, it’s safe to say that they probably didn’t have structures teeming with actual living, breathing bacteria in mind. But don’t tell that to Henk Jonkers of Delft University of Technology in the Netherlands. What he and his colleagues have developed—a self-fixing bacteria-concrete hybrid—may do more to propel sustainable architecture into the mainstream than McDonough could have ever hoped for.
While it may sound unheard of, scientists have been pressing bacteria into service in construction for years. The use of mineral-producing bacteria has already been explored in a variety of applications, including the hardening of sand and in repairing cracks in concrete. But there are two problems inherent to this approach. First, the reaction that these bacteria undergo to synthesize calcium carbonate results in the production of ammonium, which is toxic at even moderate concentrations. The other problem is a more prosaic one. Since the bacteria have to be applied manually, a worker or team of workers would have to go out every few weeks to patch up every little crack on every slab of concrete—nearly defeating the purpose of making the repair process simpler and more cost-effective.
Jonkers’ solution was to track down a different bacterial strain that could live happily buried in the concrete for prolonged periods of time. Because the bacteria would be mixed into the concrete from the start, they could immediately nip small cracks in the bud before they had a chance to expand and become exposed to water, rendering them vulnerable to further wear and tear. (Concrete structures are typically reinforced with steel bars, but these can easily become corroded when water seeps into the cracks.) Such a strain would have to endure the high pH environment of concrete and churn out copious amounts of calcium carbonate without also producing large quantities of ammonium. Read More