Cracking in concrete
Concrete is the world’s most popular building material, durability of concrete structures however always remained a concern.
Irrespective of how carefully it’s mixed or reinforced, cracking is inevitable in all types of concrete.If these cracks turn out to be too large, they may result in corrosion of the steel reinforcement, which not only ends in an unattractive look, but also affects the construction’s mechanical properties.
That’s the reason engineers usually use more than needed quantity of steel reinforcement inside concrete structure with the intention to prevent the cracks from turning into too large. This additional steel has no structural use and is an costly answer as steel costs are high. One other option to cope with cracks is to repair them, however this may be extremely troublesome in underground or liquid retaining buildings. Self Healing concrete can provide answers to all these question on which Henk Jonkers from Delft University Of Technology, Netherlands is working on.
Self Healing Process
Bacteria is used in concrete to get self healing properties. When a crack appears and water gets into those cracks bacteria gets activated and produces limestone which fills the cracks.
There are certain issues with this method as survival of bacteria is difficult because of extreme alkaline nature of cementitious systems.
Jonkers used Baccilus a type of alkaliphilic bacteria which has the capabilities to withstand such harsh environment. Another problem Jonkers encountered was feeding of these bacteria. Sugar is not good option as adding it to the mix will make it weak. He used calcium lactate which was set in capsules with bacteria and added to the mix.
Using Self healing concrete can in concept result in substantial financial savings, particularly in steel strengthened concrete. It can additionally imply durability issues could be tackled in a brand new and more economical method when designing concrete structures. Self healing concrete is good for developing underground retainers for hazardous waste, as there will be no need of humans to go there and repair those cracks.