Dutch researchers have invented a biological concrete that can seal its own cracks, preventing water ingress and corrosion of reinforcement.
The technique uses a special strain of mineral-eating bacterium that can tolerate high alkaline environments such as those found in concrete. Millions of dormant bacteria are incorporated in the aggregate during concrete production along with packets of chemical “feed”.
If the concrete is cracked and oxygen and water are introduced, the bacteria become activated. The bacteria then convert the feed into calcite, which seals the crack. Once plugged the bacteria return to their dormant state.
Delft University of Technology in Holland has successfully trialled the concrete and is working to make it commercially viable. The bacteria and feed currently costs €80 (£78) per cubic metre, roughly doubling the price of per cubic metre of concrete.
The work has been led by research scientist Henk Jonkers. He said the cost of the bacteria is small in terms of overall construction costs, but is still keen to make it more competitive.
He is working with industry partners to cut the cost of the bacteria and feed mix to £17/m3. If costs can be brought down, Jonkers believes the technique will first be used in tunnel lining segments.
“It took me over a year to come up with the right combination that would not adversely affect the concrete properties.”
“It’s difficult to persuade industry to invest in the upfront cost,” said Jonkers. “We hope to have something suitable on the market within two years for the tunnel sealant and are developing ways to reduce the cost to about £17/m3,” he added.
Jonkers and his team has spent four years perfecting the technique. “It took me over a year to come up with the right combination that would not adversely affect the concrete properties, then another three years of testing,” he said.
“The new concrete would be perfect for structures which are difficult to maintain, like underground buildings, motorways or oil rigs,” said Jonkers.
“It is extremely durable. The bacteria are specially adapted to extremely alkaline environments, and can survive dormant inside the concrete for up to 50 years.”