1. SELF HEALING BACTERIAL CONCRETE
A SEMINAR REPORT
Submitted by,
SAHEENA BEEVI ABDUL VAHAB
11428054
BACHELOR OF TECHNOLOGY
IN
CIVIL ENGINEERING
RAJADHANI INSTITUTE OF ENGINEERING AND TECHNOLOGY
JULY 2014

2. DEPARTMENT OF CIVIL ENGINEERING,
RAJADHANI INSTITUTE OF ENGINEERING AND
TECHNOLOGY,
ATTINGAL, THIRUVANANTHAPURAM
2014
CERTIFICATE
This is to certify that the Seminar Report entitled ‘SELF HEALING BACTERIAL
CONCRETE’ is a bonafide record of the seminar done by SAHEENA BEEVI ABDUL
VAHAB, Reg. No: 11428054, S7 Civil Engineering, Rajadhani Institute Of
Engineering And Technology during the year 2014 for the partial fulfillment of the
requirements for the award of the degree of Bachelor Of Technology by the
University of Kerala.
Prof.V.Janardhana Iyer
HOD
Asst.Prof
Gayathri U.V
GUI
DE

3. ACKNOWLEDGEMENT
First and foremost I concede the surviving presence and the flourishing
refinement of almighty God for his concealed hand yet substantial supervision all
through the seminar.
I would like to thank our seminar coordinator Smt. Biji.B.J and my guide
Smt.Gayathri U.V for their valuable guidance and assistance.
I sincerely thank Sri.Janardhana Iyer, Head of Department, civil engineering
for his kind co-operation and technical support rendered by him in making my
seminar a success.
I extend my sincere gratitude to our respected principal Sri.R.Sathikumar
For his countenance towards the successful accomplishment of the course.
I sincerely thank all staff of the Civil Engineering Department for providing
their valuable guidance and support
Above all I would like to express my sincere gratitude and thanks to all friends
for their valuable comments and suggestions for making this work a success.
SAHEENA BEEVI ABDUL VAHAB

4. ABSTRACT
Cracks in concrete are inevitable and are one of the inherent weaknesses
of concrete. Water and other salts seep through these cracks, corrosion
initiates, and thus reduces the life of concrete. So there was a need to
develop an inherent biomaterial, a self-repairing material which can
remediate the cracks and fissures in concrete. Bacterial concrete is a
material, which can successfully remediate cracks in concrete. This
technique is highly desirable because the mineral precipitation induced
as a result of microbial activities is pollution free and natural. As the
cell wall of bacteria is anionic, metal accumulation (calcite) on the
surface of the wall is substantial, thus the entire cell becomes
crystalline and they eventually plug the pores and cracks in concrete.
This paper discusses the plugging of artificially cracked cement mortar
using Bacillus Pasteurii and Sporosarcina bacteria combined with sand
as a filling material in artificially made cuts in cement mortar which
was cured in urea and CaCl2 medium. The effect on the compressive
strength and stiffness of the cement mortar cubes due to the mixing of
bacteria is also discussed in this paper. It was found that use of bacteria
improves the stiffness and compressive strength of concrete. Scanning
electron microscope (SEM) is used to document the role of bacteria in
microbiologically induced mineral precipitation. Rod like impressions
were found on the face of calcite crystals indicating the presence of
bacteria in those places. Energy- dispersive X-ray (EDX) spectra of the
microbial precipitation on the surface of the crack indicated the
abundance of calcium and the precipitation was inferred to be calcite
(CaCO3).

5. CHAPTER 1
INTRODUCTION
Concrete is a vital building material that is an
absolutely essential component of public infrastructure and most
buildings. It is most effective when reinforced by steel rebar, mainly
because its tensile strength without reinforcement is considerably low
relative to its compressive strength. It is also a very brittle material
with low tolerance for strain, so it is commonly expected to crack with
time. These cracks, while not compromising structural integrity
immediately, do expose the steel reinforcement to the elements, leading
to corrosion which heightens maintenance costs and compromises
structural integrity over long periods of time. That being said, concrete
is a high maintenance material. It cracks and suffers serious wear and
tear over the decades of its expected term of service. It is not flexible
and cannot handle significant amounts of strain. Self-healing concrete
in general seeks to rectify these flaws in order to extend the service life
of any given concrete structure.
There is a material in the realm of self-healing
concrete in development, now, that can solve many of the problems
commonly associated with standard concrete. This material is bacterial
self-healing concrete. Self-healing concrete consists of a mix with
bacteria incorporated into the concrete and calcium lactate food to
support those bacteria when they become active. The bacteria, feeding
on the provided food source, heal the damage done and can also reduce
the amount of damage sustained by the concrete structure in place.

6. CHAPTER 2
SELF BACTERIAL HEALING CONCRETE
Fig 2.1 Self healing bacterial concrete
Autogenously crack-healing capacity of concrete has been recognized in several
recent studies. Mainly micro cracks with widths typically in the range of 0.05 to 0.1
mm have been observed to become completely sealed particularly under repetitive
dry/wet cycles. The mechanism of this autogenously healing is chiefly due to
secondary hydration of non- or partially reacted cement particles present in the
concrete matrix. Due to capillary forces water is repeatedly drawn into micro cracks
under changing wet and dry cycles, resulting in expansion of hydrated cement
particles due to the formation of calcium silicate hydrates and calcium hydroxide.
These reaction products are able to completely seal cracks provided that crack widths
are small. Larger sized cracks can only be partially filled due to the limited amount of
non-reacted cement particles present, thus resulting in only a thin layer of hydration
products on the crack surface. With respect to crack-sealing capacity, a process
homologous to secondary hydration of cement particles is the process of carbonation.
This reaction is also expansive as ingress atmospheric carbon dioxide (CO2) reacts
with calcium hydroxide particles present in the concrete matrix to various calcium
carbonate minerals. From the perspective of durability, rapid sealing of particularly
freshly formed surface cracks is important as this hampers the ingress of water and
other aggressive chemicals into the concrete matrix.

7. Although bacteria, and particularly acid-producing bacteria, have been traditionally
considered as harmful organisms for concrete, recent research has shown that specific
species such as ureolytic and other bacteria can actually be useful as a tool to repair
cracks or clean the surface of concrete. In the latter studies bacteria were externally
and manually applied on the concrete surface, while for autogenously repair an
intrinsic healing agent is needed.. Species from Bacillus group appear promising
intrinsic agents as their spores, specialized thick-walled dormant cells, have been
shown to be viable for over 200 years under dry conditions. Such bacteria would
comprise one of the two components needed for an autogenously healing system. For
crack repair filler material is needed, and bacteria can act as catalyst for the metabolic
conversion of a suitable organic or inorganic component, the second component, to
produce this. The nature of metabolically produced filler materials could be bio-
minerals such as calcite (calcium carbonate) or apatite (calcium phosphate). These
minerals are relatively dense and can block cracks, and thus hamper ingress of water
efficiently. The development of a self-healing mechanism in concrete that is based on
a potentially cheaper and more sustainable material then cement could thus be
beneficial for both economy and environment.

8. CHAPTER 3
USE OF SELF HEALING BACTERIAL CONCRETE
Concrete will continue to be the most important building material for infrastructure
but most concrete structures are prone to cracking. Tiny cracks on the surface of the
concrete make the whole structure vulnerable because water seeps in to degrade the
concrete and corrode the steel reinforcement, greatly reducing the lifespan of a
structure. Concrete can withstand compressive forces very well but not tensile forces.
When it is subjected to tension it starts to crack, which is why it is reinforced with
steel to withstand the tensile forces.
Structures built in a high water environment, such as underground basements and
marine structures, are particularly vulnerable to corrosion of steel reinforcement.
Motorway bridges are also vulnerable because salts used to de-ice the roads penetrate
into the cracks in the structures and can accelerate the corrosion of steel
reinforcement. In many civil engineering structures tensile forces can lead to cracks
and these can occur relatively soon after the structure is built. Repair of conventional
concrete structures usually involves applying a concrete mortar which is bonded to the
damaged surface. Sometimes, the mortar needs to be keyed into the existing structure
with metal pins to ensure that it does not fall away. Repairs can be particularly time
consuming and expensive because it is often very difficult to gain access to the
structure to make repairs, especially if they are underground or at a great height.

9. CHAPTER 4
BACTERIAS USED
Cement and water have a pH value of up to 13 when mixed together, usually a hostile
environment for life, most organisms die in an environment with a pH value of 10 or
above.
In order to find the right microbes that thrive in alkaline environments can be found in
natural environments, such as alkali lakes in Russia, carbonate-rich soils in desert
areas of Spain and soda lakes in Egypt. Strains of endolithic bacteria of genus
Bacillus were found to thrive in this high-alkaline environment. These bacteria were
grown in a flask of water that would then be used as the part of the water mix for the
concrete. Different types of bacteria were incorporated into a small block of concrete.
Each concrete block would be left for two months to set hard. Then the block would
be pulverized and the remains tested to see whether the bacteria had survived. It was
found that the only group of bacteria that were able to survive were the ones that
produced spores comparable to plant seeds. They are namely bacillus pasturii, bacillus
filla and bacillus cohnii.
Fig 4.1.Bacillus cohnii Fig 4.2.Bacillus filla Fig 4.3.Bacillus parturii
Such spores have extremely thick cell walls that enable them to remain intact for up
to 200 years while waiting for a better environment to germinate. They would become
activated when the concrete starts to crack, food is available, and water seeps into the

10. structure. This process lowers the pH of the highly alkaline concrete to values in the
range (pH 10 to 11.5) where the bacterial spores become activated.
CHAPTER 5
PREPERATION OF BACTERIAL CONCRETE
Self healing bacterial concrete can be prepared in two ways.
• By direct application
• By encapsulation in light weight concrete.
By the method of direct application bacterial spores and calcium lactate are added
directly while making the concrete and mixed. Here when the crack occurs in the
concrete bacterial spores broke and bacteria comes to life and feed on the calcium
lactate and limestone is produced which fill the cracks.
By encapsulation method the bacteria and its food, calcium lactate, are placed inside
treated clay pellets and concrete is made. About 6% of the clay pellets are added for
making bacterial concrete. When concrete structures are made with bacterial concrete,
when the crack occurs in the structure and clay pellets are broken and bacterial
treatment occurs and hence the concrete is healed. Minor cracks about 0.5mm width
can be treated by using bacterial concrete
Among theses two methods encapsulation method is commonly used, even though
it’s costlier than direct application. Bacillus bacteria are harmless to human life and
hence it can be used effectively.

11. CHAPTER 6
TESTING OF BACTERIAL CONCRETE AND RESULT
Concrete disks are prepared containing the porous aggregates filled with food only
and with food and bacteria. The specimens are cured for 56 days and then tested in a
deformation controlled tensile splitting loading to crack them partially. After this
cracking the specimens are placed in a permeability test setup in which water is
applied at one side of the specimen for 24 hours. After the healing the cracks are
examined under the microscope and the results were observed.
Fig 6.1 Test samples Fig 6.2 Test setup
Also the permeability of the healed specimens was determined. The outcome of this
study shows that crack healing in bacterial concrete is much more efficient than in
concrete of the same composition but without added biochemical healing agent. The
reason for this can be explained by the strictly chemical processes in the control and
additional biological processes in the bacterial concrete. On the crack surface of
control concrete some calcium carbonate will be formed due to the reaction of CO2
present in the crack ingress water with Portlandite (calcium hydroxide) present in the
concrete mixture according to the following reaction:
CO2 + Ca(OH)2 → CaCO3 + H2O

12. The amount of calcium carbonate production in this case in only minor due to the
limited amount of CO2 present. As Portlandite is a rather soluble mineral in fact most
of it present on the crack surface will dissolve and diffuse out of the crack into the
overlying water mass. Subsequently, as more CO2 is present in the overlying water,
dissolved Portlandite will as yet precipitate in the form of calcium carbonate but
somewhat away from the crack itself, as can be seen. The self healing process in
bacterial concrete is much more efficient due to the active metabolic conversion of
calcium lactate by the present bacteria:
Ca(C3H5O2)2 + 7O2 → CaCO3 + 5CO2 + 5H2O
This process does not only produce calcium carbonate directly but also indirectly via
the reaction of on site produced CO2 with Portlandite present on the crack surface. In
the latter case, Portlandite does not dissolve and diffuse away from the crack surface,
but instead reacts directly on the spot with local bacterially produced CO2 to
additional calcium carbonate. This process results in efficient crack sealing as
can be seen .
Fig 6.3 Controlled and uncontrolled specimen
The conclusion of the test is that the proposed two component biochemical healing
agent composed of bacterial spores and a suitable organic bio-cement precursor
compound, both immobilized in reservoir porous expanded clay particles, represents a
promising bio-based and thus sustainable alternative to strictly chemical or cement
based healing agents.

13. CHAPTER 7
BIOCONCRETE MECHANISM
When the concrete is mixed with bacteria (bacillus subtilus), the
bacteria go into a dormant state, a lot like seeds. All the bacteria need
is exposure to the air to activate their functions. Any cracks that should
occur provide the necessary exposure. When the cracks form, bacteria
very close proximity to the crack, starts precipitating calcite crystals.
When a concrete structure is damaged and water starts to seep through
the cracks that appear in the concrete, the spores of the bacteria
germinate on contact with the water and nutrients. Having been
activated, the bacteria start to feed on the calcium lactate nutrient. Such
spores have extremely thick cell walls that enable them to remain intact
for up to 200 years while waiting for a better environment to germinate.
Fig 7.1 Bacterial self healing process
As the bacteria feeds oxygen is consumed and the
soluble calcium lactate is converted to insoluble limestone. The
limestone solidifies on the cracked surface, thereby sealing it up.

14. Oxygen is an essential element in the process of corrosion of steel and
when the bacterial activity has consumed it all it increases the
durability of steel reinforced concrete constructions. Tests all show that
bacteria embedded concrete has lower water and chloride permeability
and higher strength regain than the surface application of bacteria. The
last, but certainly not least, key component of the self-healing concrete
formula is the bacteria themselves. The most promising bacteria to use
for self-healing purposes are alkaliphilic (alkali- resistant) spore-
forming bacteria. The bacteria, from the genus Bacillus Subtilus is
adopted for present study. It is of great concern to the construction
industry whether or not these bacteria are “smart” enough to know when
their task is complete because of safety concerns. Bacillus Subtilus
which is a soil bacterium is harmless to humans as it is non-pathogenic
microorganism.

15. CHAPTER 8
ADVANTAGES
• Incorporation of the agent in the concrete will be relatively cheap as well as
easy when the aggregate is immobilized in porous light weight aggregate prior
to addition to the concrete mixture.
• The self healing bacterial concrete helps in reduced maintenance and repair
costs of steel reinforced concrete structures.
• Oxygen is an agent that can induce corrosion, as bacteria feeds on oxygen
tendency for the corrosion of reinforcement can be reduced.
• Self healing bacteria can be used in places where humans find it difficult to
reach for the maintenance of the structures. Hence it reduces risking of human
life in dangerous areas and also increases the durability of the structure.
• Formation of crack will be healed in the initial stage itself thereby increasing
the service life of the structure than expected life.

16. CHAPTER 9
DISADVANTAGES
• If the volume of self healing agents (bacteria and calcium lactate) mixed
becomes greater than 20%, the strength of the concrete is reduced.
• Preparation of self healing concrete needs the requirement of bacteria and
calcium lactate. Preparation of calcium lactate from milk is costlier. Hence
preparation of self healing concrete costs double than conventional concrete.

17. CHAPTER 10
CURRENT RESERCHES
There will be full-scale outdoor testing of self-healing concrete
structures. A small structure or part of a structure will be built with the self-healing
material and observed over two to four years. Structures will be fitted with some
panels of self-healing concrete and others with conventional concrete so that the
behavior of the two can be compared. Cracks will be made in the concrete that are
much larger than the ones that have healed up in the laboratory to determine how well
and fast they heal over time.
The research will test two systems. The first technique will see
bacteria and nutrients applied to the structure as a self-healing mortar, which can be
used to repair large-scale damage. The second technique will see the bacteria and food
Nutrients dissolved into a liquid that is sprayed onto the surface of the concrete from
where it can seep into the cracks. Laboratory tests are being carried out to accelerate
the ageing process of self-healing concrete. The tests will subject the concrete to
extreme environments to simulate changing seasons and extreme temperature cycles,
wetter periods and dryer periods

18. CHAPTER 11
APPLICATIONS
Self healing bacterial concrete can be used for sectors such as
tunnel-lining, structural basement walls, highway bridges, concrete floors and marine
structures.
Fig 10.1 Marine structure Fig 10.2 Base wall
Fig 10.3 Concrete flooring Fig 10.4 Tunnel lining

19. Fig 10.5 Highway bridge Fig 10.6 Underground retaining walls

20. CHAPTER 11
CONCLUSION
The bacteria which are known to be alkali-resistant, i.e. they grow in natural
environments characterized by a relatively high pH (10-11). In addition, these strains
can produce spores which are resting cells with sturdy cell walls that protect them
against extreme environmental mechanical- and chemical stresses. Therefore these
specific bacteria may have the potential to resist the high internal concrete pH values
(12-13 for Portland cement-based concrete), and remain viable for a long time as well,
as spore viability for up to 200 years is documented. We hypothesized that concrete-
immobilized spores of such bacteria may be able to seal cracks by bio mineral
formation after being revived by water and growth nutrients entering freshly formed
cracks.. Although the exact nature of the produced minerals still needs to be clarified,
they appear morphologically related to calcite precipitates.
The mechanism of bacterially-mediated calcite production likely proceeds via organic
carbon respiration with oxygen what results in carbonate ion production under
alkaline conditions. The produced carbonate ions which can locally reach high
concentrations at bacterially active 'hot spots' precipitate with excess calcium ions
leaking out of the concrete matrix. This microbial calcium carbonate precipitation
mechanism is well studied and occurs worldwide in natural systems such as oceans,
bio films, microbial mats and stromatolites. For an autonomous self-healing
mechanism all needed reaction components, or self-healing agents, must be present in
the material matrix to ensure minimal externally needed triggers. To conclude we can
state that the application of bacteria as a self-healing agent in concrete appears
promising

21. REFERENCES
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microfibers and micro particles, MSc Thesis, Delft University of Technology,
2009
• De Muynck, W., Debrouwer, D., De Belie, N., Verstraete, W., 2008. Bacterial
carbonate precipitation improves the durability of cementations materials.
Cement & Concrete Res. 38, 1005–1014.
• Bang, S.S., Galinat, J.K., Ramakrishnan, V., 2001. Calcite precipitatioinduced
by polyurethane-immobilized Bacillus pasteurii. Enzyme Microb. Technol. 28,
404-409
• Jonkers, HM & Schlangen, E. (2009a). Bacteria-based self healing concrete.
International journal of restoration of buildings and monuments, 15(4), 255-
265.
• Jonkers, HM, Thijssen, A, Muijzer, G, Copuroglu, O & Schlangen, E.
(2009b). Application of bacteria as selfhealing agent for the development of
sustainable concrete. Ecological engineering, 1-6.