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IPFS News Link • Inventions

Self-healing concrete patches up cracks with dormant bacteria

•, By Michael Irving

Now researchers at Drexel University have demonstrated a type of self-healing concrete embedded with "BioFibers" that use bacteria to patch up cracks as they form.

You don't get to be crowned the world's most-used building material without doing a few things right – concrete is easy to make, strong and, under ideal conditions, durable for long periods. But of course, the real world rarely plays to ideals, so concrete is exposed to constant weathering that can cause cracks. That's when the real trouble starts, as temperature fluctuations force the cracks wider while moisture triggers various processes that can eat away at the concrete.

As such, concrete structures need constant maintenance, which can be costly and inconvenient, as well as increasing the (already large) environmental footprint of making the stuff. Finding ways to slow that deterioration could save a lot of headaches.

That's where Drexel's BioFiber comes in. These polymer fibers not only act as physical reinforcements, but they have an important double life as a self-healing mechanism. The fibers are coated with a layer of hydrogel that contains endospores – dormant forms of bacteria that can withstand extreme environments, then revive themselves when things become more comfortable. The hydrogel layer is then coated with a thin polymer shell.

BioFiber concrete can be used like any other, but its secret superpower only becomes apparent later, when and if it cracks. When water reaches the BioFiber, the hydrogel will expand and bust out of its shell, pushing up towards the surface. In the process, the slumbering bacteria are woken, and they begin feeding on carbon and calcium from the concrete around them. This produces calcium carbonate, a cementing material that fills and patches up the crack.