About bacterial concrete, it's mechanism, It's advantages and disadvantages

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Channabasava A
Topic: Bacterial
concrete

2.  INTRODUCTION
 BACTERIAL CONCRETE
 CLASSIFICATION OF BACTERIA
 FORMS OF BACTERIUM
 MATERIALS
 METHODOLOGY
 MECHANISM
 ADVANTAGES
 CASE STUDY
 CONCLUSION
 REFERENCES
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 Concrete has a large load bearing capacity for
compression load, but the material is weak in tension.
 That is why steel reinforcement bars are embedded in
the material to be able to build structures.
 The steel bars take over the load when the concrete
cracks in tension.

4.  The presence of cracks can highly influence the strength
and durability of the concrete
 The cracks provide a path through which moisture,
chlorides, carbon dioxide and other aggressive agents
can penetrate.
 Various conventional repair methods are being used
which include materials such as mortar, epoxy and
resins, however these are not considered sustainable.
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5.  The “Bacterial Concrete” can be made by embedding bacteria
in the concrete that are able to constantly precipitate calcite.
 This phenomenon is called microbiologically induced calcite
precipitation.
 Calcium carbonate precipitation, a widespread phenomenon
among bacteria, has been investigated due to its wide range of
scientific and technological implications.
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6.  The cracks formed in concrete can be repaired in variety of
techniques available but traditional repair systems have a
number of disadvantageous aspects such as different thermal
expansion coefficient compared to concrete environmental
and health hazards.
 Therefore, bacterially induced calcium carbonate
precipitation has been proposed as an alternative and
environmental friendly crack repair technique
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Classification
of bacteria
Basis on shape
Basis on gram
stain
Basis on
oxygen
demand

9. The most commonly used bacterium in concrete are
 Bacillus pasteurii
 Escherichia colli
 Bacillus subtilis
 Bacillus sphaericus
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10.  Bacillus subtilis is also called as the grass bacillus.
 It is a common soil bacterium.
 Bacillus subtilis is a model laboratory bacterium, which can produce
calcite precipitates on suitable media supplemented with a calcium
source.
 Bacillus subtilis is used to induce CaCO3 precipitation at a faster
rate.
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11.  Bacillus sphaericus is an aerobe bacterium which
frames round endospore.
 It is a gram positive bacterium, with bar formed cells
that shape chains.
 It is an actually happening bacterium - detached,
refined, and marked for mosquito control.
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12. The materials used in Bacterial concrete are
 Cement
 Coarse Aggregate
 Fine Aggregate
 Water
 Bacteria
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13. The methodology for producing a self-healing bacterial
concrete involves the following steps:
 Selection and cultivation of bacteria.
 Preparation of test specimens.
 Characterization studies.
 Testing Procedure
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14.  Pure cultures are maintained on nutrient agar slants and
on nutrient agar plates.
 It forms irregular dry white colonies on nutrient agar
plate.
 Whenever required, few colonies of the pure culture is
inoculated into nutrient broth of 25ml in 100ml conical
flask and the growth condition is maintained at 37°C
temperature and placed in 125 rpm orbital shaker.
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17.  Bacterial concrete is casted by using ordinary Portland cement
 It is then mixed with specific bacterial concentration (cell/ml) of
water.
 Conventional concrete samples are also casted in parallel.
 The specimens are cured under tap water or tanks at room
temperature and tested at 7, 14 and 28 days.
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Fresh cubes

19.  After the obliged time of curing the shapes are expelled
from the curing tank or under tap water and tried for
compressive quality.
 The compressive strength of the cubes at 3 days, 7 days,
14 days and 28 days is resolved.
 The results will be reported for the normal of three
trials.
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20.  The Bacteria's such as bacillus subtilis and bacillus
sphaericus produces urease which catalyzes the hydrolysis
of urea (CO(NH2)2) into ammonium (NH4
+) and carbonate
 First, 1 mol of urea is hydrolyzed intracellular to 1 mol of
carbamate and 1 mol of ammonia (Eq. (1)).
 Carbamate spontaneously hydrolyses to form additionally
1 mol of ammonia and carbonic acid (Eq. (2)).
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21.  The last 2 reactions give rise to a pH increase, which in
turn shifts the bicarbonate equilibrium, resulting in the
formation of carbonate ions (Eq. (5)).
CO(NH2)2 + H2O → NH2COOH + NH3 (1)
NH2COOH + H2O → NH3 + H2CO3 (2)
H2CO3 ↔ HCO3
- + H+ (3)
2NH3+ 2H2O ↔ 2NH4
+ + 2OH− (4)
HCO3
- + H+ + 2NH4
+ + 2OH−↔CO3
2− + 2NH4
+ + 2H2O (5)
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22. Since the cell wall of the bacteria is negatively charged, the bacteria draw cations
from the environment, including Ca2
+, to deposit on their cell surface. The Ca2
+
ions subsequently react with the CO3
2− ions, leading to the precipitation of
CaCO3 at the cell surface that serves as a nucleation site (Eqs. (6) and (7)).
Ca2
+ + Cell→ Cell‐Ca2
+ (6)
Cell‐Ca2
+ + CO3
2− → Cell‐CaCO3↓ (7)
(Precipitate)

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24. Magnified image of Rod shaped impressions consistent
with the dimensions of Bacillus pasteurii, spread around
the calcite crystals
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25.  Better resistance towards freeze-thaw attack reduction.
 Improvement in compressive strength of concrete.
 Reduction in permeability of concrete.
 Reduction in corrosion of reinforced concrete.
 It helps in crack remediation.

26. CASE STUDY
Conducted an experiment on Self Healing bacterial concrete to
study calcite precipitation for achieving high strength bio-
concrete durability. It includes,
The main aim in this was to investigate the effect of Bacillus
strain bacterial in achieving strength in contrast to conventional
concrete.
The appropriate components of concrete were obtained based on
Indian Standards method.

27. Indian standard method stipulation
a) Concrete grade- M25
b) Exposure-Mild
c) Quality control-Fair
d) Size of aggregate- 20mm
e) Cement used-OPC 53 grade cement
f) Sand grading zone-iii
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Material Specific gravity Bulk density
Cement 3.14 1450
Fine aggregate 2.6 1650
Coarse aggregate 2.7 1575
Water - 1000

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Material Weight Volume (m3)
Cement 425.73 0.294
F.A 539.54 0.327
C.A 1231.77 0.782
Water 191.58 0.191
MIX PROPORTION:- 1:1.27:2.89:0.45

29. The table represents the Compressive Strength of conventional Concrete
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No of days Compressive strength(n/mm2)
7 days 20.21
14 days 27.16
Test results:-
No of days Compressive strength
7 days 29.84
14 days 31.11
Table represents the Compressive strength of concrete with 20ml
addition of bacteria

30.  It was observed that with the expansion of microscopic organisms, the
compressive quality of cement expanded up to 4.90% in 7 days, 6.26% in 14
days for a convergence of 105 cells/ml of blending water.
 Compressive quality was impressively expanded as the period of solid
increments.
 The bacterial concrete has less weight and strength loss than the ordinary
Portland cement concrete without microorganism
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31. [1] Raminandalib, Mzaimiabdmajid, Keyvanfar, Amirrezatalaiekhozan,
Mohdwaridhussin, Shafaghat, Roslimohdzin, Chew tin lee, Mohammad
alifulazzaky and Hasrulhaidarismail-“Durability improvement assessment in
different high strength bacterial structural concrete grades against different types
of acids”, Sadhana Vol. 39, Part 6, December 2014, pp. 1509–1522
[2] Ramakrishnan V. “Performance characteristics of bacterial concrete – a
smartbiomaterial”. In: Proceedings of the first international conference on recent
advances in concrete technology. America: Washington DC; 2007. p. 67–78.
[3] S.K. Ramachandran, V. Ramkrishnan, S.S. Bang, “Remediation of
concrete using microorganisms”, ACI Materials Journal 98 (1) (2001)3–9.
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