Self-Healing Bacterial Concrete

PRESENTED BY-SOUMALYA BAG

ROLL NO-20125005PAPER CODE-CE(892)

UNDER THE GUIDANCE OFMrs. APARNA ROY & Mr. SOUMEN ROY

SEMINAR REPORT ON

INTRODUCTIONCrack formation is a typical phenomenon 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.

WHAT IS BIO CONCRETEIts 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.

WHAT SPECIAL PRESENT IN BIO CONCRETEThere 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.

WHAT BACTERIA IS USEDMost of the bacteria belongs to genus bacillus are fulfilling the required criteria discussed above. some of the list of bacteria areB. Pseudofirmus , B. Cohnii B. Filla B. Pasteurii…etc

The suitable chemical precursor found to be most suitable is “calcium lactate” Ca(C3H5O2)2

CLASSIFICATION OF BACTERIASBacteria is generally classified in three categoryBasis on Shape, Basis on Gram Stain and Basis onOxygen Demand which shown in Fig. 2 and subtypes of each category also can be shown in Fig. 3,Fig. 4, and Fig. 5.

Fig.3 Classification on Basis of shape

Fig.4 Classification on Basis of Gram Stain

Fig. 5 Classification on Basis of oxygen demand 

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 …etc,

The water is deliberately forced into the crack and the precursor is activated

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

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 .

BEFORE HEALING

AFTER HEALING

20x

40x

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 strengthwhen the healing agent is added, Optimization of healing agent is necessary so that it wont affect the characteristics of concrete

EVALUATION

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.

THANK YOU