Concrete cracks for many reasons: just for starters, the heating
and cooling of changing seasons make it expand and contract, and
the stress produced as the freshly poured goo dries and shrinks
in volume, pulling against its underlying metal supports, can
also cause cracks. But Dutch researchers are testing a new way
to deal with the problem of cracking concrete: bacteria that,
when exposed to water, form limestone. The concrete mix they’ve
developed contains small ceramic pods filled with dormant spores
of the bacteria and nutrients (calcium lactate) to feed them. In
solid concrete slabs, these spores remain dormant, but when the
concrete cracks and water seeps into the ceramic pods, the
bacteria spring into action, using the calcium lactate to form
calcite, one of the two primary components of limestone, which
fills the crack. In the lab, the bacteria can fill cracks up to
0.5 millimeters wide, microbiologist Henk Jonkers told the BBC
News. Now the researchers want to test their self-healing
concrete outsid