The amazing “bioconcrete” that repairs itself

01 September 2015

Launched in 2006 by the European Patent Office, the prestigious European Inventor Awards honour the people behind some of today’s breakthrough innovations in fields like science, industry, and healthcare, among others.

Hendrik Jonkers, a microbiologist at Delft University in the Netherlands, is a finalist in the 2015 Awards. And you can see why.

He’s created a new material that could save billions of dollars a year by preventing a problem that we see every day.

Healing the cracks

Of all the world’s fascinating topics, concrete wouldn’t be near the top of the list. But throw in some serious ingenuity and creativity, and even this boring building material becomes way more interesting.
“We’ve invented bioconcrete – concrete that heals itself using bacteria,” says Jonkers.

Why would we need such a thing? Well, while concrete is obviously one of the world’s most durable materials, like most things, it becomes weaker and less effective as it gets older.

No matter how strong it is when mixed, or how well it’s reinforced, age and Mother Nature eventually take their toll…and the concrete cracks. Take a look at your local streets, bridges, parking garages…and you’ll see this for yourself.

As Jonkers says, “The problem with cracks in concrete is leakage. If you have cracks, water comes through. If this water gets to the steel reinforcements – in concrete we have all these steel rebars – if they corrode, the structure collapses.”

But Jonkers has injected science into the construction process and came up with a way for concrete to repair itself when this happens.

Preserving life with… bacteria

The secret lies in a special bacterium that’s added to the concrete mixing process. Now, ordinarily, you’d expect bacteria to break down and rot certain materials and substances. But in this case, it has the opposite effect – it produces limestone and acts as a healing agent. In fact, the bacteria actually remain stable and intact while the concrete is being mixed. They only come alive when the concrete cracks and water seeps in.
That’s where the science comes in.

The first part, Jonkers says: “You need bacteria that can survive the harsh environment of concrete. It’s a rock-like, stone-like material, very dry.” In other words, he needed a bacterium that could survive dormant for a long time (around 200 years) without needing food, water, or oxygen. No easy task.

But in bacillus bacteria, he found the perfect candidate. It loves the alkalinity of concrete, while its spores can continue to live on next to nothing.
The second part is the actual repair process – i.e. what material to use and how to get the bacteria to produce it.

Jonkers decided on limestone. But in order for the bacteria to create it, it needs some form of energy. That comes from calcium lactate. He packaged the bacteria and calcium lactate into biodegradable plastic capsules, and added them to the concrete mix.

Result? When cracks form in the concrete, the water will open the capsules and awaken the bacteria. Fuelled by the water, the bacteria germinate and multiply, feeding on the calcium lactate. In turn, the organisms produce limestone, which fills the cracks in about three weeks.

The structure quite literally comes “alive” – and “bioconcrete” is born.
Needless to say, this self-repairing bioconcrete could significantly extend the lifespan of roads, bridges, buildings – basically any concrete structures that are susceptible to age and weathering. And do so much more cheaply, too.

Jonkers’ innovation is nine years in the making – one that he says combines existing, “free” natural resources with science and construction technology. But he says his bioconcrete could pave the way for future “biological buildings.”


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