11. INTRODUCTION
Crack formation is a typicalphenomenon
related to durability.
Percolation of cracks may lead to leakage problems, causing
deterioration of the concrete matrix or corrosion of embedded
steel reinforcement.
In recent years a bacteria-based self-healing concrete is being
developed in order to extend the service life.
A two component healing agent is added to the concrete mixture.
The agent consists of bacteria and an organic mineral precursor
compound.
12. WHAT IS BIO CONCRETE
Its is a special type of concrete invented by a group of
microbiology researchers under the head of Henk Jonkers.
Bio concrete is also called as BACTERIAL CONCRETE or self healing
concrete.
Its specially made to increase
the lifespan or the durability
of concrete structure by
the self healing action
of that concrete.
13. WHAT SPECIAL PRESENT IN BIO CONCRETE
There are two thing present in bio concrete.
1) The special bacteria that has to resist the alkalinity and the
mechanical stress of concrete.
2) The chemical precursor to activate the bacteria.
14. WHAT BACTERIA IS USED
Most of the bacteria belongs to genus bacillus are fulfilling the
required criteria discussed above. some of the list of bacteria are
B. Pseudofirmus ,
B. Cohnii B. Filla B. Pasteurii…etc
The suitable chemical precursor found to be most suitable is
“calcium lactate” Ca(C3H5O2)2
15. WHAT IS HAPPENING INSIDE BIO CONCRETE(MECHANISM)
The cracks are formed on the surface of concrete due to many
reasons like shrinkage, Inadequate water for hydration …ect,
The water is deliberately forced into the crack and the precursor is
activated
16. Ca(C3H5O2)2 + 7O2 → CaCO3 + 5CO2 + 5H2O
CO2 + Ca(OH)2 → CaCO3 +H2O
(carbonation)
The activated precursor intern induces the bacteria to react with
that precursor and form a base of calcium carbonate called as
limestone, the chemical equation is given above.
24. HOW THE HEALING AGENTS ARE APPLIED
1)BY DIRECT APPLICATION
The bacteria and the chemical precursor(calcium lactate) are
added directly while making the concrete.
2) ENCAPSULATION LWA
a)The part of the coarse aggregate is replaced by the light
weight aggregate(LWA) , which is impregnated with twice the
calcium lactate solution and the spores of bacteria.
b)After impregnation the clay particles with 6% healing agents
and the concrete is made .
25. EVALUATION
• The Concrete properties should not be negatively
affected by addition of a healing agent to the
concrete mixture.
• a large amount of bacteria and certain mineral
precursor compounds like calcium lactate do
substantially influence concrete compressive and
tensile strength
• when the healing agent is added, Optimization of
healing agent is necessary so that it wont affect the
characteristics of concrete
26.
27. CONCLUSION
The spores would be crushed by smaller holes.
No strong spores were detected in a 135-day old
specimen, implying the majority of spores in the cured cement
mixture were available for less than 4 months.
Further research is needed to increase the time period that the
bacterial spores remain in the concrete. It could be possible.
