STORY OF “SELF HEALING CONCRETE”

In 1877, Ferdinand Cohn claimed that with bacteria known as Genus Bacillus concrete could be healed, in continuation of the research a team of microbiologists at The Delft University of Technology in the Netherlands, headed by Dr. Henk Jonkers , is working on how the self-healing capacity of concrete structures can be improved by using calcite-precipitating bacteria and what conditions are necessary for these bacteria to thrive.
Inspiration behind the Living concrete
Mr. Jonkers was well familiar with how bacteria behaved in nature and also he has analyzed the Self-healing octopus tentacles and plants that use offshoots to multiply. Self-healing and Self-repair is a common theme in biological systems from trees to human skin. The less severe the damage is to an organism; the easier it is for the organism to repair itself and for the repair to be strong and long-lasting.
How it Works?
Through research, Jonkers chose Bacillus pseudofirmus and Sporosarcina pasteurii bacteria that biologically produce limestone. And this new form of concrete uses microfibers in the place of coarser bits of sand and gravel that traditional cement mix uses. The fibers allow the final composite to bend with minimal fracturing and if fracturing does occur, the cracks tend to be less than 50 microns wide. When these tiny cracks form, the dried concrete absorbs moisture from the air. When it does this, the concrete in the crack becomes softer and eventually “grows” until the crack is filled in.
The secret of the self-healing concrete is in the bacteria that are mixed in the mortar. These bacteria are enclosed in pellets and can be dormant for 200 years.
Difference between Concrete and Healing concrete
The rigidity of traditional concrete leads to the formation of large cracks that can seriously degrade the integrity of important structures. Furthermore, when damage does occur to concrete, expensive and resource-consuming measures must be taken to repair the concrete, usually from the outside. Or, if repair measures are insufficient, the structure must be demolished and rebuilt which further expands the need for resources. This new cement composite, while currently three times the price of traditional concrete, promises to pay for itself with reductions in repair costs over the lifetime of the structure.
Mixing – Spores Fine aggregate + Coarse aggregate + Cement, which results in Self Healing Concrete.
But while mixing one precaution is taken that bacteria and cement are not allowed to mix together with the help of clay pellets.