The inventor, Hendrik Marius Jonkers, is a microbiologist at Delft University of Technology in Delft, Netherlands.
He came up with the idea after reflecting on how nature is self-healing, especially the human body.
Specifically, Jonkers thought about human bones and how they naturally heal via mineralization from osteoblast cells.
Inspired, he set out to create a “similar self-regeneration technique” for a common construction material – concrete (2).
How It Works
Jonkers and his team of scientists created a concrete that’s more stable than conventional concrete by adding a unique component – a limestone-producing bacteria. The scientists used bacteria found near volcanoes to create a living concrete. The bacteria, found inside stones form spores that can survive in a dormant stage for a very long time. This particular bacteria is resistant to cold and heat, which makes it ideal for a concrete application.
In addition to the bacteria, Jonkers added calcium lactate to the concrete mixture. The process sounds almost too simple to be effective, but it’s highly effective. The bacteria in the concrete remains dormant until it’s activated by water seeping into cracks. As soon as the bacteria is touched by the rain that finds its way into the concrete cracks, it comes alive or awakens.
The bacteria feeds on the calcium lactate and then secretes limestone. These secretions of limestone fill-in the cracks. Since the inactive bacteria can survive for a couple hundred years and only activates when water finds its way into the concrete, it’s an ideal choice for creating Jonkers’ self-healing concrete.
One of the common problems with concrete is the alkali silica reactions (ASR). This is a chemical reaction often found in concrete and is often responsible for the breakdown of concrete. The ASR is created by the aggregate particles found “between the alkaline pore solution of cement paste.” The bacteria used in the Jonkers self-healing concrete are “specially adapted to extremely alkaline environments” (3).
Once activated, the bacteria begin feeding on the calcium lactate, but it takes three weeks for the bacteria to produce enough limestone secretions to seal the crack. The length of the crack doesn’t limit the bacteria; it can seal any length simply by virtue of eating the calcium lactate and secreting the limestone to fill in the crevice.
In order for the bacteria to be effective, the crack must be a least “0.8mm [approximately 0.03 inches] wide or thinner”.
Self-Healing Concrete Will Save Billions of Euros
It usually takes 20 to 30 years before reinforced concrete begins to suffer from cracks due to stress and wear. Rain finds its way into the cracks and eventually penetrates the steel that in turn begins to rust. The rust spreads into the concrete, eating it away and causing it to become brittle and in need of repair.
In Europe, over 70% of the infrastructure is made up of concrete. The annual cost of repairing potholes, cracks in bridges and buildings is upwards of 6 billion Euros. With self-healing concrete, this major expense would no longer be necessary.
Jonkers is also creating a spray on liquid to repair existing cracks in roads, buildings and bridges to be released sometime in 2015. The self-healing concrete is scheduled for release sometime in 2016.
The bioconcrete has one major hurdle to overcome before it is put on the market. The price tag to manufacture is twice that of conventional concrete. The biggest factor in producing the self-healing concrete is the cost of the calcium lactate nutrient.
The team is tackling the problem by creating a “sugar-based nutrient.” If successful, this replacement component will reduce the cost. In fact, the cost would be nearly that of currently use regular concretes.
Jonkers and his team have been nominated for the prestigious European Inventory Award for 2015 (4). The award is granted by the European Patent Organization, which is an intergovernmental organization made up of “two bodies, the European Patent Office and the Administrative Council, which supervises the Office’s activities” (5).
Once the cost is in line with regular concrete, Jonkers and his team will be in a position to completely revolutionize the industry. Self-healing concrete will become the modern concrete with the capability of healing itself up to 200 years.
References & Image Credits:
(1) TSW: Amazing Real Life Nano Technology – Self-Healing Plastic
(2) Daily Mail
(3) Concrete Experts
(5) Popular Prize