A Self Healing Concrete | Bio Concrete | Building Materials
Concrete is great … what’s greater than concrete ? well the answer to this is BIO CONCRETE .
Bio concrete is self-healing concrete designed to repair its own crack . Developed by an extra ingredient using a healing agent, BIO -Concrete is set to revoultnize the building industry . It is also called self-healing concrete .
Concrete is a hard substance . It cracks under tension and effects durability and lifespan.
In a Bio-Concrete 2-component healing agent is added to mixture
- Organic Mineral Precursor compound
2 researchers from Delft technical university in the Netherlands -Henk jonkers and Eric schlangen who specializes on concrete development worked for several years on this type of concrete which has self-regenerative properties.
During experimentation , they mixed bacteria into a cement paste and after amonth they found the spores of 3 particlaur bacteria were still viable . They added aharmless bacteria bacillus genus to the concrete which remained dormant until rainwater entered the cracks which occur naturaly inside concrete. the bacteria used the nutrients, the researchers incorporated into he cement (calcium lactate).According to Joinekrs , Healing of cracks has been shown in a width of 0.5 mm . They have to produce large number of self healing agent to start outdoor test and looking at different types of concrete to see if the concept really work in practice.
Let us understand the components of Bio-concrete
A special bacteria that has to resist the alkalinity and the mechanical stress of concrete.
Bacteria belonging to Genus Bacillus are fulfilling the required criteria . Some of the useful bacteria are
The chemical precursor to activate the bacteria. The suitable chemical precursor for this mixture is calcium lactate CA(C3H5O2)2
How does it WORK
The cracks are formed on the concrete due to many reasons like shrinkage, tension , load , inadequate water for hydration etc . The water is deliberately forced into the crack and the precursor is activated .
The activated precursor intern induces the bacteria to react with the precursor and form a BASR of calcium carbonate called as Limestone.
CA(C3H5O2)2 +7O2 = CACO3 + 5CO2 +5H2O
CO2 +CA(OH)2 = CACO3 =H2O
The bacteria and the chemical precursor are added directly while making concrete .The part of the coarse aggregate is replaced with light weight aggregate which Is impregnated with twice the calcium lactate solution and spores of bacteria .
The main challenge of the self-healing concrete is to ensure that the healing agent can survive the mixing process. Coating healing agent particles is an expensive process.
How to keep bacteria dormant(SLEEP) till it is needed …..
Bacteria is placed in a small biodegradable capsules contiantint the nutrient. When the concrete cracks and water enters the gaps , it contact with bacteria and the food source .setting the healing process . then bacteria then feed on the calcium lactate joining the calciumimestone fixing the crack .
Very efficient and can be added to liqud and then sprayed on to exitng buildings .