Accidently, human bones gets cracks and doctors used to put Plaster Of Paris by keeping the bones in exact position without disturbing the fractured bones. Look at small video:
Thanks to ORTHOfilms for
the video.
Why does concrete cracks: Please refer to this blog to know more about this. https://annayyachandrashekar.blogspot.com/2017/11/blog-post.html
Microbiologist, Mr. Hendrik Jonker used the same system to heal the concrete as human bones does. He mixing concrete with limestone-producing bacteria ( Bacillus pseudofirmus or Sporosarcina pasteurii, are found naturally near volcanoes, and they are capable of surviving for up to 200 years without oxygen or food) and tested. Once concrete cracks, water and other particles starts entering in to the concrete, including the mixed bacteria, and get activated with water, bacteria use calcium lactate as a food source and produces limestone in a result which closes up the cracks.
Because of modern technology and advanced science, now we
are able to make the concrete to repair the cracks itself. This concrete is
named as Bio Concrete / Self Healing concrete. Since, this concrete gets it
ability of self healing because of use of some bacteria, hence it is also
termed as Bio Concrete. And, as this concrete can repair/ heals itself, it has
been named as Self Healing concrete.
In fact, Self Healing Concrete is available in 2 different types and are as follows:
1. Biotic Concrete
2. Abiotic Concrete
In direct method, agents are directly added to the cement mixture while making concrete in a designed ratio. Whereas, in Encapsulation method, self-healing agent is capsulated (using a different type of shell material and geometric properties) and added in concrete.
Microbial enhanced crack-healing ability is presumably due to combined direct and indirect calcium carbonate formation:
i) Direct CaCO3 precipitation through metabolic conversion of calcium lactate.
ii) Indirect formation due to reaction of metabolically produced CO2 molecules with Ca(OH)2 minerals present in the concrete matrix leading to additional CaCO3 precipitation.
Advantages of Bio Concrete: No need to replace the old concrete at all, decreases concrete maintenance cost (repair costs of steel reinforced concrete structures such as building, bridges, dam and others) and improves the strength and durability of the concrete. Bacteria feed on oxygen, so, tendency for the corrosion of reinforcement can be reduced. Self-healing bacteria can be used in places where humans find it difficult to reach, so it reduces risking of human life in dangerous areas. Crack will be healed in the initial stage itself thereby increasing the services life of the structure than expected life.
Disadvantages of Self-Healing concrete: Cost is high as it
quite new in market BUT, maybe in future, the cost gets reduce when self
-healing concrete will become common. Still no any constructions codes were
made to use / test / approve the Self-Healing concrete. You will not get Contractor
/ applicator to install this at present. Volume of self-healing agents such as
bacteria and calcium lactate mixed will lose it’s volume once get reacted, then,
it will leads to the reduction the strength of the concrete.
Many thanks to Google and DTAK.com from where the details
are collected.
Do let me know if you have any comments....
