Self-Healing Concrete

Posted by Chuck Harrell on Feb 16, 2016 11:00:00 AM

concrete.pngIt may be the greatest building material ever invented, but concrete has some serious problems.   No matter how well mixed and reinforced, it is susceptible to cracks and corrosion caused by water seeping into the holes and rusting the steel reinforcements.   In normal situations, builders fill the hole to stop more water getting in.  But, to do this, they either have to wait until the hole is large enough to insert the filler or they have to make the gap larger and then repair it.  Neither of these are ideal situations.

But now, Professor Henk Jonkers, of Delft University of Technology, in the Netherlands has developed a self-healing concrete.  According to Jonkers, Bioconcrete heals itself using bacteria.  The concrete mixes in the same fashion as normal concrete but when it cracks and gets wet, the healing agent is activated.  As the normally dormant bacteria are activated by water dissolving their housing, they begin feeding on their food source and product limestone which strengthens and adheres to the existing concrete.

Because of the very dry alkaline environment inside concrete, it took three years for Jonkers to find the precise bacteria that could survive in these conditions without food or oxygen.  Through much experimentation , the Bacillus bacteria was found to be the best bacterium.

Once the bacteria was found, the next question was what they should eat so they can grown and multiply.  Normally, bacteria survives on sugars but that causes soft weak concrete.  To get around this problem, Jonkers discovered that using calcium lactate would produce the most effective solution since as they feed on the calcium they create calcite or limestone which then closes the gap.

What happens now is that dry powder containing bacillus and the calcium lactate is combined with the concrete mix and remains in its dry form until dissolved by water and stirs the bacteria into life filling the tiniest of gaps and preventing any more water getting in.

Although, all concrete will eventually crack, in countries such as China and Japan where earthquakes can open hairline fractures as soon as the building goes up, bioconcrete will help these building maintain their structural integrity for a lot longer.

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