'Bioconcrete' uses bacteria to heal itself

Dutch researchers have developed a self-healing cement that turns water-logged cracks to its advantage.

No product evokes a sense of solidity and sturdiness the way concrete does. However, the tiniest of cracks in an otherwise colossal slab will inevitably lead to structural degradation, leakages and costly repairs.

It is precisely this problem that two Dutch researchers from Delft Technical University have been working on. Beginning in 2006, Henk Jonkers, a microbiologist, and Eric Schlangen, a specialist in concrete development, sought to develop a self-healing cement [pictured] that would stop cracks from forming in the concrete, thereby extending the life of constructions.

Microcracks have a width of just 0.2-0.4mm, but that’s enough for water to leak in, degrading the concrete and the steel reinforcements embedded within it. Using the potentially damaging water to their advantage, Jonkers and Schlangen added a healing agent into the concrete, composed of bacterial spores and a feed.

Jonkers explains that the incoming water activates the bacterial spores, causing them to convert the feed into limestone, which seals the crack. Tunnels, basements and highway infrastructure are ideal ‘wet environments’ which will benefit from this innovation.

Rachel Armstrong, senior lecturer in the School of Architecture and Construction at the University of Greenwich, calls the project “a landmark in developing ‘living’ materials”.

However, “the production of calcite does not appear to me to actually increase the structural integrity of the concrete: [it] just stops the progression of the faults”, Armstrong added.

While this bacteria-infused cement is not alone in the world of self-healing concrete, Jonkers and Schlangen’s concrete has succeeded in healing cracks 10 times longer than other methods.

At present, the biggest challenge is producing large-scale quantities of the healing agent at affordable costs.

With the hope of long-term savings from the increased life expectancy of constructions, several companies and stakeholders have expressed interest in the product, including the Dutch ministry of road affairs.

The two researchers expect their concrete to enter the market in about four years. – Kyla Mandel

Photo: Henk Jonkers