The Phenomenon of Self Healing Concrete

 

Self healing concrete hits the market this year, and it’s got some new tricks that building owners and contractors just might be ready to pay for.

 

Made to build buildings, pave roads and span bridges, concrete is one of the most commonly and widely used construction materials. In spite of having a considerable demand, the problem with it is that it cracks due to air, water and chemical exposure.

 

Concrete structures are strengthened and laced with rebar to help keep fissures small. Unfortunately, not small enough to heal. Cracks and fissures get larger when water, chloride and deicing salts seep into them and that makes the structure weaker.

 

Now, a six-year experiment and study inspired by the human body, has delivered a way for concrete to heal itself. Professor Henk Jonkers at Delft University of Technology in the Netherlands created the self healing concrete using bacteria. He mixed batches of  concrete and added a bacteria that produces limestone. Into the mix also went the bacteria’s favorite food, calcium lactate.  Air and moisture triggers the bacteria to eat the calcium lactate which it  converts to calcite, and seals the cracks.

 

The bacteria can lie dormant in placed work for 200 years, waiting for the right conditions, which can reduce building maintenance costs, and improve performance. The product works also in underground and underwater applications where it might find its initial market.

 

The product is expensive at $33 to $44 per square meter as it waits for wide acceptance and more demand. Jonkers is already at work trying to reduce the cost by substituting a less expensive food for the bacteria.

 

People have known for many years that concrete will heal itself to a certain degree. They have noted a crystalline structure in cracks of very old concrete and speculated the activity of rainwater and carbon dioxide mixing with chemicals in the concrete created healing action. Experiments of immersing damaged concrete in water, and using compressive loading on deformed young concrete also had restorative effects.

 

Since concrete develops micro cracks even during construction, this innovation can be a solution for this long standing problem. Imagine a building that can patch itself up without the need of human hands!

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