Bacterial Concrete or Self Healing Concrete For Crack Repairs
Bacterial Concrete or Self Healing Concrete For Crack Repairs
Bacterial Concrete or Self Healing Concrete For Crack Repairs
In modern days, the use of technology has taken the standards of construction to a new
high level. Different types of procedures, methods and materials are used to attain a very
good, sustainable and economic concrete construction.
But due to human mistakes, incorrect handling and unskilled labors. An efficient building is
hard to sustain its designed life. Many problems like weathering, cracks, leaks and bending
etc., arises after the construction.
To overcome this types of problems, many remedial procedures are undertaken before and
after the construction.
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The common problem found in buildings is Crack. Crack may be due to many reasons. Some
reasons are listed below,
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10/11/2018 Bacterial Concrete or Self Healing Concrete For Crack Repairs
Table of Contents
It can be observed that small cracks that occur in a structure of width in the range of 0.05
to 0.1mm gets completely sealed in repetitive dry and wet cycles. The mechanism of this
autogenously healing is, the width of range 0.05-0.1mm act as capillary and the water
particles seep through the cracks. These water particles hydrate the non or partial reacted
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cement and the cement expands, which in turn fills the crack.
But when the cracks are of greater width, need of other remedial work is required. One
possible technique is currently being investigated and developed was based on application of
mineral producing bacteria in concrete.
The bacteria used for self-healing of cracks are acid producing bacteria. These types of
bacteria can be in dormant cell and be viable for over 200 years under dry conditions. These
bacteria acts as a catalyst in the cracks healing process.
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Bacillus pasteurizing
Bacillus sphaericus
Escherichia coli
Bacillus subtilis
Bacillus cohnii
Bacillus balodurans
Bacillus pseudofirmus
Special type of bacteria’s known as Bacillus are used along with calcium nutrient known as
Calcium Lactate. While preparation of concrete, this products are added in the wet
concrete when the mixing is done. This bacteria’s can be in dormant stage for around 200
years.
When the cracks appear in the concrete, the water seeps in the cracks. The spores of the
bacteria germinate and starts feeding on the calcium lactate consuming oxygen. The soluble
calcium lactate is converted to insoluble limestone. The insoluble limestone starts to harden.
Thus filling the crack, automatically without any external aide.
The other advantage of this process is, as the oxygen is consumed by the bacteria to
convert calcium into limestone, it helps in the prevention of corrosion of steel due to cracks.
This improves the durability of steel reinforced concrete construction.
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Fig: Process of fixing crack in concrete
By direct application
By encapsulation in lightweight concrete
In the direct application method, bacterial spores and calcium lactate is added into concrete
directly when mixing of concrete is done. The use of this bacteria and calcium lactate
doesn’t change the normal properties of concrete. When cracks are occurred in the structure
due to obvious reasons.
The bacteria are exposed to climatic changes. When water comes in contact with this
bacteria, they germinate and feed on calcium lactate and produces limestone. Thus sealing
the cracks.
By encapsulation method the bacteria and its food i.e. calcium lactate, are placed inside
treated clay pellets and concrete is prepared. About 6% of the clay pellets are added for
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10/11/2018 Bacterial Concrete or Self Healing Concrete For Crack Repairs
When concrete structures are made with bacterial concrete, when the crack occurs in the
structure and clay pellets are broken and the bacteria germinate and eat down the calcium
lactate and produce limestone, which hardens and thus sealing the crack. Minor cracks
about 0.5mm width can be treated by using bacterial concrete.
Among these two methods encapsulation method is commonly used, even though it’s
costlier than direct application.
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The limestone then hardens itself and seals the cracks in the concrete.
1 7 20.85 27.10
2 28 30.00 38.95
Compressive Strength Test result for 7 and 28 days for Bacterial Concrete
NORMAL CONCRETE
SL NO
DAYS (N/mm2) BACTERIAL CONCRETE (N/mm2)
1 7 3.90 4.6
7.80
2 28 7.05
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Fasi Ur Rahman
Fasi is a Civil Engineer who works as an Engineer in Tumkur Smart City Project. He is the author, editor and partner
at theconstructor.org
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