Bacterial Concrete- A Self Repairing Biomaterial PRESENTATION BY Akash Bhardwaj

Shaheed Bhagat Singh State Technical Campus Ferozepur

IntroductionCracking of Concrete is an inevitable

phenomenon.Remediation of already existing cracks

has been the subject of research from many years.

The various products such as structural epoxy resins, other synthetic mixtures are used as a filling agents for repairing concrete.

The use of Epoxy resins is neither Eco-friendly nor safe for human health.

ObjectivesTo Study the strength regaining capacity

of the cracked specimens remediated with different bacterial class.

To study the durability aspects of bacterial concrete and its resistance towards freeze-thaw attack , sulphate attack, alkaki aggregate attack.

To Identify microscopic evidence using scanning electron microscopy supporting bacterial participation in mineral precipitation.

HOW DOES BACTERIA REMEDIATE CRACKS?HOW DOES BACTERIA REMEDIATE CRACKS?CHEMISTRY OF THE PROCESSCHEMISTRY OF THE PROCESS

Microorganisms (cell surface charge is negative) draw cations including Ca2+ from the environment to deposit on the cell surface. The following equations summarize the role of bacterial cell as a nucleation site.

Ca2+ + Cell Cell-Ca2+

Cell-Ca2+ + CO32- Cell-CaCO3

The bacteria can thus act as a nucleation site which facilitates in the precipitation of calcite which can eventually plug the pores and cracks in concrete

Visual Aspects of Bacteria in ConcreteBacteria Efficency in Different

medium Concentrations .Bacterial inherent ability to

precipitate calcite continiouslyBacteria Survival Duration in

Specimen.Reaction Tendency of Different

Types of Bacteria under Different medium Concentrations.

Bacterial Classification :-

In this study the four different kinds of bacteria were used and comparison results are based on them, these are classified as:-

B. PasturiiB. SubtilesB. SphaericusB. Cohnii

Formation Mechanism (B.Pasturii)B . Pasturii is formed by the

mechanism of oxidative determination of amino acids and the nutrients required for its formation are:-

TrypticaseYeast extractTricineAgar solutionGlutamic Acid

Formation Mechanism (B.Subtiles)

B . Subtiles is formed by the

mechanism of Hydrolysis of Urea

and the nutrients required for its

formation are:-UreaCalcium saltsAmmonium chlorideSodium Bicarbonate

Formation Mechanism (B. Sphaericus)

B . Sphaericus is formed by the

mechanism of bio oxidative

analysis of Urea and the nutrients

required for its formation are:-UreaYeast ExtractCalcium Salts

Formation Mechanism (B. Cohnii)

B . Cohnii is formed by the

mechanism of bio oxidative analysis

of Urea and the nutrients required

for its formation are:-PeptoneYeast extractActicalNatamycine

SCANNING ELECTRON MICROSCOPY INVESTIGATIONSCANNING ELECTRON MICROSCOPY INVESTIGATION

To give a visual documentation of the extent of mineral precipitation in various regions within the cement mortar.

To characterize the microstructure relationship of the precipitates and the filling material.

To confirm the elemental composition of the mineral precipitates.

To identify microscopic evidence supporting the participation of bacteria in mineral precipitation.

XRD AnalysisXRD provides most definitive

structural information.It uses monochromatic beam for

sample analysis.Single crystal differaction

mechanism is adopted in XRD.XRD is based on the indexing the

patterns.Most effective in cubic

specimens.

Microstructure Examinations:-It is based on the micrograph

obtained by scanning electron microscopic analysis.

From the micrograph it was investigated the growth of rod shaped fabulous deposition in concrete with bacteria.

It also reveals the calcifying power of the different bacterial micro-organisms and their interaction with concrete.

Magnified image of full-grown calcite crystals with distinct and sharp edges, found in the interior surface of the crack.

Magnified image of full-grown calcite crystals with distinct and sharp edges, found in the interior surface of the crack.

Rod Shaped Deposition on Concrete Surface

Rod-shaped impressions, consistent with the dimensions of B. pasteuriiare spread around the calcite crystals, formed on the surface of the

specimens subjected to sulfate attack.

Rod Shaped Impressions

Rod-shaped impressions, consistent with the dimensions of B. pasteuriiare spread around the calcite crystals, formed on the surface of the

specimens subjected to sulfate attack.

Rod Shaped Impressions

Developing Calcite Crystals

Bacterial Endospores

Developing calcite crystals, at the surface of the specimen subjected to deicing chemical attack. Presence of endospores consistent with the

dimensions of B. pasteurii, indicated microbial activity.

Bacterial Endospores

Developing calcite crystals, at the surface of the specimen subjected to deicing chemical attack. Presence of endospores consistent with the

dimensions of B. pasteurii, indicated microbial activity.

Magnified Image of Calcite Crystals

Magnified image of calcite crystals developed on the surface of the cement mortar beams with bacteria subjected to alkali aggregate

Reactivity, thus increasing the impermeability.

Magnified image of calcite crystals developed on the surface of the cement mortar beams with bacteria subjected to alkali aggregate

Reactivity, thus increasing the impermeability.

Durability Comparison

Comparison of change in durability factor for specimens made with and without bacteria and subjected to freeze thaw cycles

100 100 100 100

86.11 87.5291.81 92.05

0

20

40

60

80

100

Control1 Control2 Bacteria1 Bacteria2

Mix Designation

Du

rab

ilit

y F

acto

r.

0 cycles

300 cycles

Compressive Strength Comparision Bacteria Specimen

Compressive Strength

B. Pasturii 30

B. Subtiles 33

B. Sphaericus 28

B. Cohnii 29

Conclusion

CONCLUSIONSCONCLUSIONS It was found that beams with micro cracks remediated with a bacterial

(Bacillus pasteurii) concentration of 8.6108 cells/ml regained 81.97% of its original strength.

Higher concentrations reduced the regaining strength of the beams. It was found that all the specimens with bacteria formed a layer of calcite

at the surface, thus improving its impermeability and its resistance to alkaline environment, sulfate attack, deicing chemicals and freeze-thaw.

Scanning Electron Microscope was used to document the role of bacteria in improving the durability aspects of concrete.

Thus it can be concluded that cracks remediated with bacteria can improve the strength and the durability of the structure.

ACKNOWLEDGEMENTSACKNOWLEDGEMENTS The authors gratefully acknowledge the support for the research by the

National Science Foundation under contract number CMS-9802127. The SEM analyses were conducted in the Engineering and Mining Experiment Station of the South Dakota School of Mines and Technology under the guidance of Dr. Edward Duke.

B . Subtiles is found to be most effective microbiome for the crack remediation as it remediates the crack easily and helps in development of strength in early age.