Materials Today: Proceedings 33 (2020) 3148–3154

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Experimental anaylsis of self healing properties of bacterial concrete

Partheeban Pachaivannan a,⇑, C. Hariharasudhan b, M Mohanasundram b, M. Anitha Bhavani c
a
Chennai Institute of Technology, Kundrathur, Chennai, India
b
Department of Civil Engineering, Chennai Institute of Technology, Kundrathur, Chennai, India
c
Department of Civil Engineering, St. Peter’s College of Engineering and Technology, Avadi, Chennai, India

a r t i c l e i n f o a b s t r a c t

Article history: The necessity of excessive sturdiness for structures uncovered to harsh environment together with sea-
Received 22 March 2020 floor, tunnels, sewage pipes and structures for strong, liquid waste containing poisonous chemical com-
Accepted 28 March 2020 pounds and radioactive elements won’t be accomplished using these days’s Ordinary Portland Cement.
Available online 25 April 2020
This study makes a speciality of growing the energy and total durability of the concrete utilized in con-
temporary via introducing bacteria (Bacillus subtilis). It reveals a phenomenon called bio-calcification as a
Keywords: part of its metabolic activity. It is the technique via which the micro-organism externally secretes calcium
Bacillus subtilis
precipitate, in which the occurrence of a carbonate ion forms CaCo3 which fills up the voids within the
Bacterial precipitation
Compressive strength
concrete texture hence making it greater compact. This in flip enriches the strength in concrete due to
Flexural strength boom of the filler fabric within the pores of the concrete mixer. A comparison have a look at was made
Tensile strength with concrete cubes and beams subjected to compressive, tensile and flexural strength exams which
might be casted with and without the bacteria. The compressive strength was 16.09%, 17.5% and
19.51% more when tested with 14 days old bacterial concrete at 7th, 14th and 28th day as that of con-
ventional concrete. The Split tensile strength was 14%, 16.5% and 17.8% more when tested with 14 days
old bacterial concrete at 7th, 14th and 28th day as that of conventional concrete. And the flexural
strength increased up to 9.95%, 12.3% and 14.24% for 14 days old concrete at 7th, 14th and 28th day as
that of conventional concrete. The experimental results prove that the process of bacterial precipitation
has increased the overall strength and durability characteristics of the concrete.
Ó 2019 Elsevier Ltd. All rights reserved.
Selection and peer-review under responsibility of the scientific committee of the International Confer-
ence on Nanotechnology: Ideas, Innovation and Industries.

1. Introduction solution chemistry that results in over saturation and mineral pre-
cipitation. Use of these Bio mineralogy concepts in concrete results
Concrete is the building material most widely used. It is known in ability invention of recent fabric known as Bacterial Concrete.
to have several limitations despite its versatility in construction. It Bacillus pasteurii, Bacillus sphaericus, E. coli and so forth. are the
is weak in tension, has limited ductility and little cracking resis- distinct bacteria used within the concrete. An attempt turned into
tance [24]. Specific changes were made from time to time to made inside the gift study using the micro organism Bacillus sub-
resolve the shortcomings of cement concrete based on the ongoing tilis. The principal advantage of embedding bacteria into the con-
research carried out around the globe. Newly, it is discovered that crete is that it may precipitate calcite continuously [25]. This
microbial mineral precipitation because of metabolic perfor- phenomenon is known as calcite precipitation (MICP) prompted
mances of favorable microorganisms in concrete stepped forward microbiologically [10]. Calcium carbonate precipitation, a large
the overall conduct of concrete. The method can arise interior or phenomenon amid bacteria, has been examined due to its exten-
outdoor the microbial cellular or maybe a ways away within the sive variety of scientific and technological implications [23]. Bacil-
concrete. Often bacterial activities virtually trigger a exchange in lus subtilis JC3 is a laboratory cultured soil bacterium this is long
rod formed, zero.6-zero.8 lm in width, 2.0 to a 3.0 lm in period,
gram tremendous and arise in abnormal, dry, white and opaque
⇑ Corresponding author. colonies. And its effect at the energy and durability is studied right
E-mail addresses: parthi011@yahoo.co.in (P. Pachaivannan), hariharasudhanc@- here [20].
citchennai.net (C. Hariharasudhan), mohanasundaramm@citchennai.net (M Moha-
nasundram).

https://doi.org/10.1016/j.matpr.2020.03.782
2214-7853/Ó 2019 Elsevier Ltd. All rights reserved.
Selection and peer-review under responsibility of the scientific committee of the International Conference on Nanotechnology: Ideas, Innovation and Industries.
 P. Pachaivannan et al. / Materials Today: Proceedings 33 (2020) 3148–3154 3149

A novel technique is adopted by the employ of microbiologi- to a width of 0.5 mm. Calcium carbonate will be formed on the
cally induced calcite (CaCO3) precipitation in remediation of cracks control concrete surface as a result of the CO2 reaction with cal-
and fissures in concrete [13,22]. Microbiologically induced precip- cium hydroxide present in the concrete matrix as follows:
itation of calcite (MICP) is a process that falls within a wider
CO2 + Ca(OH) ! CaCO3 + H2 O
science category called biomineralization [15]. Calcite precipita-
tion may be caused by Bacillus subtilis JC3, a common soil bac- In this situation, the production of calcium carbonate is due to a
terium. CaCO3 demonstrated its positive potential as a microbial limited amount ofCO2. Since Ca(OH)2 is a soluble mineral, it is dis-
sealant in selectively consolidating model fractures and surface fis- solved in water and diffused in the form of leaching out of the
sures in granites and consolidating sand [1,23]. The method can be crack [3,25].
employed to enhance the compressive electricity and stiffness of
cracked concrete samples. The bacterial concrete makes employ 3.1. Enhancement of strength and durability
of calcite precipitation with the aid of bacteria. The phenomenon
is known as Microbiologically Induced Calcite Precipitation (MICP) Owing to the effective metabolic processing of calcium nutri-
[3,4,9,15,21,26,27]. ents via bacteria in concrete, the self- healing process in bacteria
is much more successful [19].
2. Review of literature
Ca(C3 H5 O2 )2 + 7O2 ! CaCO3 + 5CO2 + 5H2 O

Beena Kumari [5] gave an overview of microbial concrete uses. But only because of microbial metabolic processes, this system
It has established traditional remedies and non-conventional creates calcium carbonate directly, but also indirectly because of
remedies for remediation of concrete crack. Microbes help in min- autogenous healing. This method leads to an effective technique
eralization in microbial concrete, which induces precipitation of of bio- based crack sealing. By converting urea into ammonium
calcium carbonate that is employed as a non-conventional remedy and carbonate, ureolytic bacteria such as Bacillus subtilis JC3 can
to remediate cracks in building materials. The effect of different precipitate CaCO3 in the high alkaline climate [14,17]. Locally, urea
microbes on different properties and concrete efficiency was ammonia oxidation raises the pH and facilitates the microbial
studied. deposition of carbonate as calcite crystals in a calcium-rich envi-
Farzana Rahman et al. [10] reviewed the significant research in ronment while preserving the pH of concrete [8]. The cracks can
cement and concrete for the application of microbiologically consequently be sealed through these induced crystals. In this
induced precipitation. Calcite is precipitated by highly urease- experimental work, by means of accomplishing water permeability
positive bacteria such as Sporosarcina pasteurii in the biomineral- checks, ultrasound transmission measurements and visual investi-
ization process. These microorganisms decompose urea into gation, the enrichment of concrete energy and durability houses
ammonia and carbon dioxide, increasing the pH of the surrounding due to induction of micro organism is studied. Factors such as
environment that causes dissolved calcium carbonate to precipi- the concentration of dissolved inorganic carbon inside the form
tate. The calcium carbonate adheres to any material’s surface and of vitamins available, the pH of the environment, the provision of
can act as binders between particles inthis way. Moreover, such calcium ions and the presence of nucleation websites determine
precipitation of impermeable calcium carbonate can also act the microbial precipitation of calcite crystals. The first three ele-
within porous medium as a filler material. It has also shown pro- ments are primarily based at the micro organism species added
mise as micro crack filler when applied to mortar cubes or beams within the metabolic system, whilst the final thing is based at
externally. MICP has recently been used in concrete as a dormant the micro organism’s cell membrane.
self- healing agent. MICP is a biological, pollutant-free process
and thus generates immense researcher’s attraction. 4. Determination of strength of bacterial concrete
Seshagiri Rao et al. [23] tried to incorporate dormant but viable
bacteria into the concrete matrix that would contribute to the con- The control mixes were made for M25 grade concrete. The var-
crete’s strength and durability. Water entering the concrete stimu- ious ingredients used in the mixes are as per tables of IS 10262-
lates the dormant bacteria, which in turn gives concrete strength 1982 and IS 456-2000 [6,7,12]. Casting of Specimens was done
through the cycle of precipitation of metabolically mediated cal- by batching of materials, preparation of moulds and placing of con-
cium carbonate. Concrete is a rather hostile environment for com- crete in the moulds.
mon bacteria due to its high internal pH, relative dryness and lack
of nutrients required for growth, but there are some extremophilic
4.1. Collection of materials
spore forming bacteria that may be able to survive in this environ-
ment and increase cement concrete strength and durability. Over-
4.1.1. Cement, fine aggregate and water
view of bioengineered concrete development with bacterial strain,
The Portland Pozzolana Cement was used to prepare the cement
Bacillus subtilis JC3 and its enhanced mechanical and durability
mortar specimens, which confirms IS 1489:1991. Consistency test
characteristics is studied.
was carried out for cement as per IS code 4031: 1988. The cement
grade used was M25. Locally available, IS 650:1991 clean river
3. Self-healing process using bacteria sand has been used as a fine aggregate for the entire research pro-
ject. Distilled water is preferred for mixing and curing cement mor-
In concrete, the cracks are healed autogenously when its width tar specimens in this research work. The same water is then used
is up to 0.2 mm. Such micro cracks are acceptable because they do to prepare nutrient broth solution for the growth of bacterial spe-
not directly affect the concrete’s safety and strength. Research has cies and the casting and curing process of microbial cement mor-
shown that autogenous healing occurs due to hydration of non- tar. Water/Cement ratio 0.47 was used to entire research work.
reacted cement particles in the concrete matrix when it comes into
contact with the intake water resulting in micro cracks being 4.1.2. Nutrient broth
closed. Nevertheless, autonomous crack healing of concrete Nutrient Broth is procured from Sisco Research Laboratories,
micro-cracks may still occur due to variance. The built-in self- Pallikaranai and the chemical composition is given in Table 1.
healing process based on bacteria was found to repair cracks up Nutrient Broth acts as the bacteria’s growth medium [14,19]. It
3150 P. Pachaivannan et al. / Materials Today: Proceedings 33 (2020) 3148–3154

Table 1 be held for 20 days. The solution provides an unpleasant smell that
Composition of Nutrient broth. confirms bacteria’s growth. To get the optimal concentration of
Composition Gm/lit. bacteria, the medium has to be held for 20 days. The solution gives
Peptone 5.00 an unpleasant smell that confirms bacteria’s growth [4].
Sodium Chloride 5.00 Bacteria are harmful to health and can lead to infection, there-
Yeast extract 2.00 fore precautions must be taken. It is compulsory to use gloves
Meat extract 1.00 while dealing with bacterial solution. Upon pouring the bacterial
solution, the flask has to be warmed.

helps for the cultivation and maintenance of a wide variety of

microorganisms. 4.2. Casting of bacterial concrete

4.1.3. Bacillus subtilis The 150 mm  150 mm  150 mm cubical molds were cleaned
Bio-mineralization, in the context of cement-based materials and inspected against the joint movement. On the inner surface
more specifically bio-calcification, is a series of biochemical reac- of the Moulds a coat of oil was applied and kept ready for the con-
tions, followed by calcium carbonate accumulation. The bio- creting operation. Meanwhile, when cement, fine aggregate and
calcification cycle is performed in the presence of urease enzyme coarse aggregate for the M25 mix are precisely weighed for con-
[10,16]. The most easily controlled reaction for carbonate produc- creting, the required quantities are weighed. Fine aggregate and
tion is urea hydrolysis, which is likely to produce calcite in a short cement have been thoroughly mixed in such a way that the mix-
time. There are a number of bacteria known to show the activity of ture’s color is even. Weighed quantity is then added to the coarse
urease. The ability of the bacteria to produce urease is commonly aggregate. Then there was added calculated quantity of bacterial
used in microbiologically induced precipitation [8]. Microbes like solution and water and mixing continued for about 3 to 5 min to
those of the species Bacillus lead to the production of microbial obtain a uniform mixture. Now the wet concrete is poured into
concrete by biomineralization. Microbial Type Culture Collection the molds and compacted by hand for 3 layers. In a compressive
(MTCC Chandigarh, India) procured Bacillus subtilis. Bacillus subtilis strength testing machine, the corresponding identification marks
cells are gram-positive, rod-shaped bacteria found naturally in soil were labeled over the finished surface and tested for strengths of
and vegetation. Bacillus subtilis develops in the range of mesophilic 7, 14 and 28 days [18].
temperatures and has the ability to precipitate calcium carbonate
which is an integral part of the concrete matrix and allows full
occupancy in the concrete matrix. The newly produced mineral
4.2.1. Mix proportions
precipitates based on calcium carbonate should then serve as a
Mix proportion M1 consists of no bacteria, M2 consists of bac-
type of bio- cement which effectively cures newly formed cracks
teria of 7 days old, M3 consists of bacteria of 14 days old.
[5].

4.1.4. Preparation of bacterial solution

4.2.1.1. Mix design. For 1 m3 of concrete
B4 broth medium is prepared with 0.5 percent yeast extract, 0.5
percent glucose and 1 percent calcium acetate solution and shack-
Cement: 12 bags (600 kg/m3)
led with 150 rpm to grow and multiply the microorganism at 30 °C
Fine Aggregate: 723 kg/m3
for three days. The supernatant was expanded to the optical den-
Coarse Aggregate: 1050 kg/m3
sity (600 nm) of 1 in the UV/VIS spectrometer after centrifugation.
It is used to produce a wide variety of micro-organisms in gen-
For casting 27 cubes (150  150  150 mm) and 27 cylinders
eral. A liquid medium, it is developed according to the formula of
(Radius – 50 mm and Height – 200 mm) 0.13 m3 concrete is
the Association of Official Agricultural Chemists (AOAC) of the
needed.
American Public Health Association (APHA) and promotes the
For 0.13 m3 of concrete
growth of a wide variety of microorganisms that are not very nutri-
tionally demanding. This medium is used as a basis for preparing
Mix proportion 1:1:2 (M25 grade concrete)
media supplemented with other nutrients in compliance with
Cement: 78 kg
the officially prescribed protocols for bacteriological analysis of
Fine Aggregate: 94 kg
water, milk, dairy products and feces of clinical samples [1].
Coarse Aggregate: 137 kg
Two 250 ml conical flasks containing distilled water are mainly
added with 12.5 g of nutrient broth (media). The product used con-
The quantity of material required for the preparation of conven-
tains 5.0 g of peptone and 1.0 g of distilled water meat extract per
tional concrete mixes and bacterial concrete mixes that are pre-
liter. The product used contains 5.0 g of peptone and 1.0 g of dis-
pared with 7 days old and 14 days old bacteria is shown in the
tilled water meat extract per liter. It is then filled with a thick cot-
Table 2.
ton plug and the paper and rubber band make this air tight. The
solution must be contamination-free. So it’s got to get heated. It
is then sterilized for approximately 10–20 min using a cooker. Table 2
The optimal sterilization temperature was 120°C. Timer was set Quantities of materials required.
and 20 min of sterilization was completed. Now the solution is free Materials Mix 1 Mix 2 Mix 3
of toxins and before the bacteria are added, the solution is pure
Cement (kg) 26 26 26
orange in colour. Bacteria- free solution (only media) is in clear Fine Aggregate (kg) 31.33 31.33 31.33
orange colour. The flasks will be opened later and exactly 1 ml of Coarse Aggregate (kg) 45.66 45.66 45.66
the bacterium will be applied to the sterilized flask and held over- Bacteria (ml) NIL 250 250
night. The bacterial solution was discovered as a whitish yellow Mix 1 – Conventional Concrete
turbid solution after 24 h. This demonstrates bacteria’s growth. Mix 2 – 7 days old bacterial concrete
To get the optimal concentration of bacteria, the medium must Mix 3 – 14 days old bacterial concrete
 P. Pachaivannan et al. / Materials Today: Proceedings 33 (2020) 3148–3154 3151

4.2.2. Mixing of concrete

In electrically operated mixer, the mixing process is done. The
products are put in uniform layers, in order one on the other –
coarse aggregate, fine aggregate, and cemented material. To get a
uniform color, dry mixing is done. In addition to the water, the
required amount of bacteria (Bacillus subtilis JC3) is added. The
workability tests will be performed immediately after concrete
mixing.

4.2.3. Growth of bacteria

On the nutrient broth, Bacillus subtilis JC3 which has been
allowed to grow in the bacterial medium is kept constantly. This
appears on conical flask irregular dry white colonies. It is then
Fig. 2. Cube in UTM after application of load.
taken and separated and allowed to grow in two conical flasks of
250 ml. Nutrient Broth taken for measurement is shown in the
Fig. 1.
it is necessary to determine the tensile strength of concrete. The
5. Testing of concrete splitting tensile strength is calculated using the formula

5.1. Determination of compressive strength Tsp ¼ ð2P=pDLÞ

where
Compressive strength test is the most important of many tests
applied to the concrete, which gives an idea of all the characteris-
P = applied load
tics of concrete. One judges by this single test whether or not Con-
D = diameter of the specimen
creting has been done properly. One determines by this single test
L = length of the specimen
whether or not Concreting has been done properly. Concrete com-
pressive strength depends on many factors such as water cement
The Fig. 3 shows a concrete cylinder after it has been subjected
ratio, cement density, concrete content performance and quality
to loading.
control during concrete production, etc. The Fig. 2 shows the con-
crete cube in UTM after application of load.
5.3. Determination of flexural strength
Compressive strength ¼ Load=Area N=mm2

where, Beam samples were casted for optimal mixing after 28th day
and tested for flexural conduct. The 1200  200  200 mm size
Load is in Newton (N) beam was exposed to two loading points to reveal the RCC beam’s
Area is in mm2 behaviour. As the load increases, the width of the crack is also
enhanced and extended to the top of the beam. RCC beam failure
mode was flexure due to steel yield in the tension zone. The con-
5.2. Determination of Split tensile strength crete was crushed and crushed. Comparison was made of conven-
tional concrete beam flexural strength, beam with 7-day bacterial
One of the fundamental and important properties is the tensile concrete and 14-day bacterial concrete. The test results show
strength of concrete. A method for determining the tensile strength higher load carrying capacity of bacterial concrete beams, energy
of concrete is the splitting of the tensile strength test on concrete absorption capacity and deflection, and lower rigidity and ductility
cylinder. Because of its porous nature, the concrete is very soft in compared to conventional concrete beams [18]. The Fig. 4 shows
stress and is not supposed to withstand direct tension. Once the mode of failure of RCC beam.
exposed to tensile forces, the concrete develops cracks. Therefore,
to determine the load at which the concrete members can break,

Fig. 1. Nutrient Broth taken for measurement. Fig. 3. Cylinder after application of load.
3152 P. Pachaivannan et al. / Materials Today: Proceedings 33 (2020) 3148–3154

Fig. 4. Failure mode of RCC beam.

6. Results and discussion

Fig. 5. Comparison of compressive strength of concrete.
The overall improvement in characteristics of concrete due to
use of bacteria is assessed here. The compressive strength, split
tensile strength and flexural strength of bacterial concrete and con- Table 4
ventional are compared from the experimental results obtained. Results of Split tensile strength test.

Day of Conventional 7 Days Old Bacterial 14 Days Old Bacterial

6.1. Comparison of compression strength Testing Concrete (N/ Concrete (N/mm2) Concrete (N/mm2)
mm2)
The compressive strength test was carried on with 3 cubes of 7th day 1.14 1.21 1.3
conventional concrete on 7 th, 14 th and 28 th day. And the average 14th 2.41 2.63 2.81
day
of the test results was found be 9.75 N/mm2, 16.98 N/mm2 and
28th 3.44 3.81 4.05
26.5 N/mm2. And the results with that 7 days old bacterial concrete day
were found to be 9.57 N/mm2, 21.18 N/mm2 and 29.73 N/mm2.
And for 14 days old bacterial concrete, the results were found to
be 11.11 N/mm2, 22.76 N/mm2 and 31.67 N/mm2. From the Table 3,
we can see that bacterial concrete has higher compressive strength
than normal conventional concrete. The graphical representation
of the comparison is shown below in Fig. 5.

6.2. Comparison of split tensile strength

The Split tensile strength test was carried on with 3 cubes of

conventional concrete on 7 th, 14 th and 28 th day. And the average
of the test results was found be 1.14 N/mm2, 2.41 N/mm2 and
3.44 N/mm2. And the results with that 7 days old bacterial concrete
were found to be 1.28 N/mm2, 2.68 N/mm2 and 3.84 N/mm2. And
for 14 days old bacterial concrete, the results were found to be
1.4 N/mm2, 2.76 N/mm2 and 4.2 N/mm2. From the Table 4, we
can see that bacterial concrete has higher tensile strength than
normal conventional concrete. The graphical representation of
the comparison is shown below in Fig. 6. Tensile test is the prime
test compared to other examines method. Tensile property is the
foremost important property of the material [28–35]. Fig. 6. Comparison of Split tensile strength of concrete.

6.3. Comparison of flexural strength Table 5

Results of Flexural strength test.
The Flexural strength test was carried on with 3 cubes of con-
Day of Conventional 7 Days Old Bacterial 14 Days Old Bacterial
ventional concrete on 7 th, 14 th and 28 th day. And the average
Testing Concrete (N/ Concrete (N/mm2) Concrete (N/mm2)
of the test results was found be 6.85 N/mm2, 7.59 N/mm2 and mm2)
7th day 6.85 7.01 7.47
14th 7.59 8.20 8.86
Table 3
day
Results of Compression strength test.

Day of Conventional 7 Days Old Bacterial 14 Days Old Bacterial 8.45 N/mm2. And the results with that 7 days old bacterial concrete
Testing Concrete (KN/ Concrete (KN/m2) Concrete (KN/m2)
m2)
were found to be 7.01 N/mm2, 8.20 N/mm2 and 9.02 N/mm2. And
for 14 days old bacterial concrete, the results were found to be
7th day 9.57 9.91 11.11
7.47 N/mm2, 8.86 N/mm2 and 9.95 N/mm2. From the Table 5, we
14th 16.98 17.45 19.95
day can see that bacterial concrete has higher flexural strength than
28th 26.5 29.73 31.67 normal conventional concrete. The graphical representation of
day the comparison is shown below in Fig. 7.
 P. Pachaivannan et al. / Materials Today: Proceedings 33 (2020) 3148–3154 3153

Fig. 7. Comparison of Flexural strength of concrete.

Fig. 9. Comparison of Ductiility of concrete beam.

6.4. Stiffness and ductility factor of beams

harmful solutions (alkali, sulphate, etc.,) thereby diminishing the
The Stiffness and ductility characteristics of the concrete cubes deleterious effects that they may cause. This increase in the
made with bacteria were tested and compared to that of standard strength of the matrix would have led to a lower mean expansion
concrete beam. Under lateral monotonic loading, the rigidity factor and eventually would have increased the concrete’s overall dura-
of RCC and bacterial concrete beams was calculated and the com- bility performance. The higher the dose of bacteria, better the per-
parison chart was drawn as shown in Fig. 8. Compared to the RCC formance of durability.
beam, the bacterial concrete beam shows lesser Stiffness. Under
lateral monotonic loading, the ductility factor of RCC and the bac-
terial concrete beam beams was determined and the comparison
7. Conclusions
diagram drawn is as shown in Fig. 9. Compared to RCC beam, the
bacterial concrete beam shows higher ductility.
The experimental work reveals that Bacillus subtilis can be pre-
The microbe Bacillus subtilis has been used here for the purpose
pared in the laboratory and proves to be safe because its level of
of microbiologically induced precipitation, which in turn increases
biosafety is only 1 and it is a bacterium found in the soil. As the
the strength and durability of concrete. Dormant bacteria are
density of bacteria increases, the precipitation of calcite decreases.
embedded in a concrete matrix that activates once external water
Bacterial concrete water absorption has a lower rate compared to
reaches them through the cracks. Calcium carbonate, which fixes
conventional concrete; this is owing to the micro-organisms acti-
the freshly formed cracks, is precipitated when initiated. After
vated calcium carbonate development in concrete voids, resulting
the biodeposited calcite seals off the cracks and natural concrete
in a lower void and therefore a lower permeability. It is possible
pores, healing is achieved. It seals the direction of entry leading
to stop the intake of liquids and ions starting incorporated corro-
to a decrease in permeability to gas and capillary water absorption
sion and thus increase the concrete’s overall strength and durabil-
while enhancing concrete’s strength and resilience characteristics
ity characteristics. The compressive strength test conducted on the
[2,11]. The compressive strength, split tensile strength and bacte-
7th, 14th and 28th day of curing shows that the strength increased
rial concrete flexural strength are comparatively higher than con-
to 3.55%, 2.76% and 12.2% for 7- day bacterial concrete and up to
ventional concrete from the test results. The following important
16.09%, 17.5% and 19.51% for 14- day bacterial concrete. Likewise,
reasons are attributed to improved bacterial concrete performance.
the results of the flexural strength check showed an increase of up
Formation of a new additional layer on the surface of the already
to 2.34%, 8.04% and 6.75% for 7 days old bacterial concrete and
existing concrete layer occurs. This new additional layer of calcite
9.95%, 12.3% and 14.24% respectively for 14 days old bacterial con-
formed by bacteria is highly insoluble and increases the specimen’s
crete. Split tensile strength results showed up to 6.14 percent, 9.13
impermeability. Thus it resists the penetration into the concrete of
percent and 10.8 percent for bacterial concrete aged 7 days and 14
percent, 16.5 percent and 17.8 percent for bacterial concrete aged
14 days. Likewise, the results of the flexural strength check showed
an increase of up to 2.34%, 8.04% and 6.75% for 7 days old bacterial
concrete and 9.95%, 12.3% and 14.24% respectively for 14 days old
bacterial concrete.
The results show that the concrete added Bacillus subtilis has a
compressive, flexural, and split tensile strength that is compara-
tively higher. Also the SHC beam stiffness factor was 26.2 percent
lower than conventional beams and the ductility factor of the bac-
terial concrete beam was 4.92, while conventional beam factor was
4.02. The microbes employed in making the concrete cubes and
beams has been shown to be efficient in enriching the concrete’s
properties by attaining a very high initial strength improve and
so we can infer that the calcium carbonate created has filled some
percentage of void size, making the surface more compact and
resistive to filtering. Once bacterial concrete is fully prepared,
Fig. 8. Comparison of Stiffness of concrete beam. OPC and its hazardous impact on environmental pollution may
3154 P. Pachaivannan et al. / Materials Today: Proceedings 33 (2020) 3148–3154

become another alternative method to substitute. As it is also [18] V. Nagarajan, T. Karthik Prabhu. M. Gowri Shankar, P. Jagadesh, A Study on the
Strength of the Bacterial Concrete Embedded with Bacillus Megaterium, Int.
resistant to corrosion, it can also be used for building.
Res. J. Eng. Technol. 4 (12) (2017).
[19] K. Neha Singla, Sanjay Sharma, Jasvir Singh Rattan, An Experimental
Declaration of Competing Interest Investigation on Properties of High Strength Bacterial Concrete (Bacillus
Subtilis), in: International Research First International Conference On
Advances In Civil Infrastructure And Construction Materials, 14-15, MIST,
The authors declare that they have no known competing finan- Dhaka, Bangladesh, 2015.
cial interests or personal relationships that could have appeared [20] A. Pradeep Kumar, Akila Devi, A. Anestraj, S. Arun, Santhosh kumar, An
to influence the work reported in this paper. Experimental Work on Concrete by Adding Bacillus Subtilis, Int. J. Emerg.
Technol. Eng. 2 (4) (2015)
[21] V. Ramakrishnan, R. Panchalan, S.S. Bang, Bacterial Concrete- A Self
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