Importance of Self-Healing Concrete

This dissertation aims to understand the importance of self-healing concrete and its applications in the future of civil engineering. It discusses the mechanism of self-healing concrete, its applications, and the cost-effectiveness and sustainability of using this material. The research findings suggest that self-healing concrete is a cost-effective and sustainable alternative to normal concrete, with limited applications currently but potential for future development.

Dissertation - “Self-Healing
Concrete”

ACKNOWLEDGEMENT

ABSTRACT
Aim: “To understand the importance of self-healing concrete and its applications in future of civil engineering”
Methodology: In order to conduct this research the research methodology that has been used covers an inductive
approach. Further, the data that is used in this dissertation are collected from the secondary sources and is qualitative
in nature. The type of philosophy that is required to conduct this researcher is the interpretivism.
Findings: It can be analysed that SHC is a cost-effective and sustainable element that is more beneficial than the
normal concrete. It has been analyzed that SHC being a less permeable material restricts the entry of
foreign substances that increase the strength and thus, a durability of the structure. SHC uses
biological constituents for healing and thus, it does not affect the environment by emitting CO2.
The use of SHC reinforcement should be prevented in health care homes and schools due to the
hazards that are caused by bacteria. it is observed that the production cost of SHC was obtained
comparatively higher which impacts upon its productivity. From the above, it can be analyzed
that presently there is very limited application of the self-healing concrete but in future, there
will be more areas where development can be made. Researchers are trying to find the
effectiveness of the process under different environmental conditions and area.

TABLE OF CONTENTS
TITLE: “Self- Healing Concrete” ..................................................................................................................................1
CHAPTER 1 - INTRODUCTION .................................................................................................................................1
1.1 Background....................................................................................................................................................1
1.2 Rationale........................................................................................................................................................2
1.3 Significance...................................................................................................................................................2
1.4 Aim and Objectives.......................................................................................................................................3
1.5 Research Questions........................................................................................................................................4
CHAPTER 2 LITERATURE REVIEW (LR)................................................................................................................5
2.1 Introduction....................................................................................................................................................5
2.2 Self-healing concrete and its importance......................................................................................................5
2.3 Mechanism and application of self-healing concrete..................................................................................12
2.4 Effectiveness of the self-healing process.....................................................................................................17
2.4.1 Self-healing Attributes. .................................................................................................................17
2.4.2 Robustness Criteria........................................................................................................................18
2.4.3 Robustness in its approaches.........................................................................................................19
2.5 Cost-Benefit Analysis and sustainability of self-healing concrete..............................................................20
CHAPTER 3: RESEARCH METHODOLOGY..........................................................................................................22
3.1 Introduction..................................................................................................................................................22
3.2 Methods, tools and techniques.....................................................................................................................22
Chapter 4: Data Analysis..............................................................................................................................................26
4.1 Introduction..................................................................................................................................................26
4.2 Thematic analysis........................................................................................................................................26
CHAPTER – 5 CONCLUSION AND RECOMMENDATION .................................................................................35
5.1 Conclusion...................................................................................................................................................35
5.3 Recommendations .......................................................................................................................................36
REFERENCES..............................................................................................................................................................38

ILLUSTRATION INDEX
Illustration 1: Types of Cracks in Concrete....................................................................................................................6
Illustration 2: Self_healing techniques............................................................................................................................8
Illustration 3: Difference between the different processes............................................................................................11
Illustration 4: Mechanism of healing process...............................................................................................................13
Illustration 5: Bacillus sphaericus under microscope....................................................................................................14
Illustration 6: Self-healing process...............................................................................................................................15
Illustration 7: Mix-proportions of cementitious composite materials based on the self-healing design......................32
Illustration 8: Mixing proportion of concrete...............................................................................................................32
Illustration 9: Mix-proportions of binder......................................................................................................................32

TITLE: “Self- Healing Concrete”
CHAPTER 1 - INTRODUCTION
1.1 Background
Concrete is a popular material broadly used in the construction of buildings and large civil structures. The
disadvantage that spoils proper functioning of this material is its tendency of getting cracked quite easily when
tension is applied. Considering a situation in which cracks developed in a concrete structure are not sustained but
self-repaired by the material itself (Van Tittelboom and De Belie, 2013). The fact is that such kind of material exists
because it will be very helpful in developing future infrastructure which will be having very robust structure. The
process of recovery which involves direct intervention by the subject that has experienced defects or faults is self-
healing. This new concrete or the self-healing concrete is a quintessential element which has transformed the world
of civil engineering.
Intrinsic characteristics of concrete had largely influenced civil engineering companies to incorporate this
element in building basic structures. However, scientific researches have enlightened the fact that long term use of
concrete is less favorable in the non-ideal environment. There is the development of cracks when concrete is
subjected to continuous pressure in harsh environments (Šavija and et. al., 2016). For instance, rains, earthquakes
and heavy flow of wind lead to movements in the developed structure which further leads to weakening of the entire
structure. Before implementing any new material or element as a step of advancement, it is important to check the
validity and effectiveness of the concerned material.
There is about 4.3 billion tons of production of cement every year (Bacterial Concrete or Self Healing
Concrete For Repair of Cracks in Structures, 2017). This figure is increasing annually due to growing demands of
population and the need to provide facilities and efficient infrastructure to every individual. It is significant that use
of technology has to be installed in a creation of elements and materials that are durable to very harsh environments
and build-up conditions. Mainly, the requirement of an advanced concrete which holds better durability and
resistance to easy cracking was realized a few decades back. The Self-healing concrete was developed by Hendrik
Jonkers in 2006 (Nishiwaki and et. al., 2014). This particular invention opened doors for various other new areas
which can be developed through the effective use of technology.
One of the major causes of breaking of concrete has been leakage. The cracks that are developed due to
certain uncertain conditions leads are grown into much deeper pathways for breakdown because of water leakage.
The water that flows because of leakage or rains causes the cracks to widen and reach the steel reinforcements which
have are the skeletal structure of the building or entire humongous structure (Williams, Kirisits and Ferron, 2017).
This means that chemical reactions and oxidations take place which deteriorates the material qualities and causing
the concrete to break. However, bio-concrete or Self-Healing concrete is a safe and effective technique which helps
in resolving such major civil engineering issues.
1.2 Rationale
The purpose of research is conducted has to be made clear to the readers and in the mind of the researcher . Hence, a
rationale is provided to set clear understanding regarding the reasons that have led to adoption of this research study.
1

The present research on "Self-healing concrete" is intended to dissolve the literature gaps which have been prevalent
in this area. The emerging researchers were not able to completely substantiate whether the use of self-healing
concrete can be useful in developing large scale civil engineering projects. Through this research study, there are
certain recommendations provided to enlighten this area. Additionally, this study on "Self-healing concrete and its
importance" is conducted to contribute to the academic and professional development of presenter (researcher). The
information gathered and structuring of a dissertation adds valuable knowledge to the researcher's experience.
Hence, this study has been conducted and elaborated in the form of a dissertation . Further, it will show the
importance of self healing concrete and how it can reduce the cost of maintenance and repair cost.
1.3 Significance
The relevancy and importance of a study are described in the significance element of the dissertation . The
contributions and value additions which will be made through this research in the existing literature is recognized
through understanding of significance. In many countries, there is research going on this topic. Scientific researchers
are identifying the new ways by which they can make changes in this fields (Schlangen and Sangadji, 2013).
Moreover, the use of the concrete has effectively increased. In most of the developed countries as concrete provides
more features than cement so they are mostly used in the civil constructions. However, as the construction gets older
so its repair and maintenance cost is also increased. In the UK, major construction is made from the concrete. It was
estimated that are many civil structures which required maintenance and repair works. These accounted for more
than 45% in the construction and building industry and expenditure of the more than £40 Billion ( Talaiekhozan
and et.al, 2014). Along with this, same conditions can be seen in the other countries also for example, in the US
there were more than $5.2 billion of the amount that was spent in this areas for reconstructing or modifying the
bridges. In Asia also maintenance and repair have accounted for more than $2 trillion for making their infrastructure
more stronger and better for the longer duration.
As per the research, that is conducted in this areas, self-healing concrete can completely remove the repair
and repair-cost in the civil construction areas by 50%. There are many techniques and methods that can be used in
this areas to recover the damage made due to aging and climatic conditions. Further, these techniques also cater the
concrete more strength and durability which in result increase the strength of the overall civil structure (Van
Tittelboom and De Belie, 2013). Additionally, advancement in this techniques can be seen as they can self-
detect the cracks and repair them autonomously without the interference of the humans. Following points of
consideration help in determining the significance of this study on “the importance of Self-healing concrete”:
 This study contributes certain valuable findings and information to the existing literature on self-healing
concrete.
 Through this research, individuals aspiring their career and profession in civil engineering activities shall
be benefited. The knowledge about such a unique material will enhance their field work competencies.
 It will provide guidance to the civil engineers about the proper usage of self-healing concrete and the
effectiveness of using this concrete in future infrastructure.
2

 The information of this research is helpful in developing pathways for innovative sciences when
modernized civil engineering structures are considered.
1.4 Aim and Objectives
A directional flow is quite important when devising a research study. This flow of information is acquired
when the aim and objectives are defined in the appropriate manner. The main aim of this research study is "To
understand the importance of self-healing concrete and its applications in future of civil engineering".
Following objectives have been defined for this research study on “Self-healing concrete”:
 To study the importance of self-healing concrete.
 To understand the mechanism of self-healing concrete.
 To analyze the applications of self-healing concrete in future of civil engineering.
 To recommend ways by which these methods can become cost-effective and sustainable in future
1.5 Research Questions
The research questions are strategically developed for enhancing the quality of research. The researcher
develops a set of questions which help in covering every perspective of the research and thus producing a better
quality informative content. Below mentioned are the research questions for this dissertation on “Self-healing
concrete”:
 What is self-healing concrete?
 How does self-healing concrete work when applied in civil structures?
 What is the importance associated with self-healing concrete?
 What are the properties of self-healing concrete?
 What are the advantages and disadvantages associated with self-healing concrete?
 Explain cost-effectiveness and sustainability of self-healing concrete?
3

CHAPTER 2 Self-Healing ConcreteLITERATURE REVIEW (LR)
2.1 Introduction
The part of the report is about the LR where important discussion about the research is mentioned. The
section is derived from various studies and sources so that study can be made be more positive aspects. Here
mentioned topic is elaborated and details related to the research objectives are identified. A major topic which will
be discussed under this part is importance of self healing concrete, mechanism related to it. Further, applications of
self healing concrete in future of civil engineering and recommendation on ways for developing innovative
application through the above things in the near future are evaluated.
2.12 Self-healing concrete and its importanceCracks in concrete
According to Alhalabi and Dopudja (2017), concrete has played a major role in the
construction since past Roman Empire. which It was later modified into Portland cement. It is
most versatile used material for the construction purpose. It has provided many advantages in the
civil branch., and in In this,ese the major contribution was made by François Coignet in the year
1853. He was French industrialist who wanted to construct the a building with the help of
concrete (Qian and et. al., 2015). It is began to be considered as the most effective, versatile and
economical material. This which increased its utilization in the mentioned field of construction.
However, as mentioned by the Fre and et. al. (2013), cracks have mostly affected the utilization
of the concrete. They decrease itsthe strength and holding capacity of the concrete. Though the
tensile strength of concrete it has is 10% more than compressive strength, but duringwhen steel
reinforcement, is there cracks are developedgenerated. Further, there are otherdifferent reasons
as well which generates cracks in concrete. The mentioned figure below will clearly help to
understand different types of cracks which affect the strength of concrete.
4

As shown in the figure above, cracks develop at two phases and hence are categorized as those
developing before hardening and after hardening. Cracks that develop after hardening are further
classified into four types. These are physical, chemical, structural and thermal cracks. Before
hardening, three types of cracks may develop. These include early frost, plastic and
5
Figure 1: Types of Cracks in Concrete
Illustration 1: Types of Cracks in Concrete
(Sources: Francesco, 2014)

constructional movement cracks. There are various reasons due to which cracks develop after
hardening. These consist of drying shrinkage, accidental overload, design load, thaw cycles etc.
in contrast to this, cracks developing before hardening may be due to plastic shrinkage, plastic
settlement, form- work movement and sub-grade movement.
As stated by Ramadan, Suleiman and Nehdi (2017), there are two different ways which cause
cracks in the concretecracks developing in concrete may of two different types. These are
intrinsic and structural cracks. The former one is caused due to chemical action and changes
made in the physical state while the laterlatter was is concerned withabout the changes that are
caused by the direct loading. When concrete is affected by the chemical action the main reasons
behind it is the plastic settlement, cement carbonation, and thermal movements. There are
various standards and codes made so that cracks can be prevented., Ddespite all these, the
material gets cracks appear in the material in the development stage (Victor and Emily, 2012).
Cracks affect the concrete by reducing its strength and making it vulnerable in making forming a
structure. They also and decreaseing its durability. Another reason which causes the cracks is
the corrosion caused in the Iron. Due to thea presence of the alkalinity, the material (Iron) gets
degraded and corrosion is caused. Moreover, if there is the presence of oxygen and moisture, it
affects the material adversely them also the material will get affected. All these are the reasons
which makes concrete weakness and affects its durability.
Wang and et. al., (2014) made the statementasserted that there was the only solution
thatwhich can help the concrete to regain its strength and durability was to make it self-healing
so that it can maintain and repair itself. For this purpose, there were many types of researches are
being undertakengoing on which can help to improve the strength on concrete performance.
Based on the research findings, dDifferent chemicals, bacteria, and elements are added in the
structure so that cracks prevention can be donemade. Various approaches are made adopted by
the scientists to improve the performance and strength of the cement (Van Tittelboom and et. al,
2015). One such technique/technology is mentioned below, Self-healing Concrete.
In the earlier period, civil construction was made through the specified and fixed values/
specification which werewas mentioned in the standards. If the material gets deterioratedion,
then repair and maintenance were considered as an effective solutions. But, until 1962, tThe
engineers wereas unable to find an effective solution which couldan prevent the damage until
1962 (VQureshi, Kanellopoulos and Al-Tabbaa, 2016). The development that was made was not
6

based on the concrete, but on the polymers. Later in the same field, many researchers were made
and advancedment in the technologies wereas developedmade related to the self-healing
properties technology of thermoplastic and cross linkage polymer (Van Tittelboom and De Belie,
2013). In late 1990, there was research made by Dr. Carolyn Dry conducted a research, in which
hethey applied the polymer concept to concrete. However, they lack in the fieldthe research was
not successful.
Esser-Kahn, A. P. and et.al., (2010)In the year 2011, Research's was published by White et.al.
carried out a research stating about " Programmable microcapsules from self-immolative
polymersNature about the self-healing in polymer based materials". This was another step
towards the concept of autonomous repair. Healing can be defined as repairing or curing. Self-
Healing iswas the ability by which self-cure or repair can be done. In concrete, these damages
can be self-healed through the similar changes as seen in the human biological system. All living
beings have the ability to self-heal and their damaged parts get regenerated. The sSame
technology was can be used in the concrete to make them it self-healing. In the beginning, the
damages are viewed. This is followed by adopting a and then three stage procedures are
followed (Gilabert, and et.al., 2017). These stages are Damage perception, healing mechanism
and transport system which completes the healing mechanism.
2.2 The healing process
There are various approaches through which healing mechanism can be applied. Broadly,
there are two categories in which the self-healing processes of cement based material can be
classified. These are Autogenic self-healing and autonomic self-healing. Autogenic healing is the
process in which cracks are healed by material through its own generic constituents. In contrast
to this, autonomic self-healing is concerned with use of engineered additions into the
cementitious material. It was mostly classified in three categories these are Intrinsic, Biological
based and chemical based. Under the intrinsic methods, healing agents are not used and changes
are made in the cementitious material. Through other techniques such as Autogenics healing the
repairing procedures is carried out.
Biological Based is the process in which micro- organism are used such as bacteria which
helps in making the changes. They are added in the form of a paste which releases the
precipitates that help to recover the blockage and cracks (Wang, 2013). It is more eco- friendly
7

and the approach does not require much of the approach. The last methods were changes made
through the chemical based, under which healing or repairing is done through the application of
the artificial healing chemicals which are present in nature. There is a use of the system which is
stated as encapsulation in the vascular system which helps to repair the cells. Direct changes can
be seen in the cracks. A figure of self-healing techniques for the reinforced concrete is mentioned
below.
The above figure provides a clear classification of techniques of self-healing. It shows three
broad categories namely intrinsic, biological based and chemical based.
8
Figure 2: Self-healing techniques
Illustration 2: Self_healing techniques
(Sourceas: Sankilichitti, 2016)

The healing process is classified in three categories namely, Intrinsic, Biological based and
chemical based. Under the intrinsic methods, healing agents are not used and changes are made
in the cementitious concrete substance or material. Biological Based is the process in which
micro- organisms such as bacteria are used which help in making the desired changes. These
micro- organisms are added in the form of a paste which releases the precipitates that help to
recover the blockage and cracks (Wang, 2013). It is considered as a more eco- friendly approach.
Under chemical based method, healing or repairing is done through the application of the
artificial healing chemicals. Encapsulation is another method through which properties of
construction material can be enhanced. It is regarded as a versatile and effective strategy for self-
healing. This comprises of using capsules for providing mechanical protection to the healing
agent. The capsules release the healing agents only when they are triggered by the cracks
(through diffusion or rupture) (Gupta and Kua, 2016).
One such method that is Bbiological based self-healing concrete is explained below.
Bio-mimicry is used by the engineers in the civil construction so that cracks can be
repaired naturally. It is more environmentally friendly and cost effective methods. Bio- concrete
is an invention mimics the principle on the basis of which cracks in bones are healed in human
body. In Bio- concrete, the healing agent comprises of bacteriaThey which areare mixed into the
concrete. Various aerobic and anaerobic bacteria are used as healing agent. They have special
properties that they can make the minerals into their precipitates form after coming in contact
with water and oxygen. These minerals which act as remediate to the cracks. Minerals like
carbonates, Metal-oxides, Silica, Sulphides, etc are used in it. In mid 1990, the ideas were
introduced by the Gollapudi et. al. As per his research precipitation can be caused by the
proteolytic bacteria when they are injected in the Concrete (Wang and et. al., 2014). It is
dependent on multiple factors such as pH levels, growth environment and concentration in which
they are injected. They can effectively survive through the presence of alkaline medium,
inorganic carbon and calcium ions concentration. It is based on the simple chemistry where
negative charge is attracted from the positive charge ions and precipitation is formed.
9

The chemical reaction is mentioned below:
When a crack develops, the bacteria come into contact of oxygen and water. Multiplication and
germination of bacteria occurs in calcium based nutrient, calcium lactate. The bacteria feed on
lactate and combine calcium with carbonate ions. This leads to the formation of limestone which
performs the function of sealing the cracks. Moreover, there are many aerobic and anaerobic
bacteria are present which can form precipitate. In order to make the Cell-CaCO 3 precipitates,
they use ammonia and carbonates which are easily available in the concrete in the form of urea
(Formia, and et.al., 2016, Van Belleghem and et.al., 2016). It can be easily decomposed into
carbonates and ammonia. The chemical reaction can be started by 1 mole of CO 32- and NH 4+.
Thus, a chain reaction is formed and the concrete gets self-repaired (Williams, Kirisits and
Ferron, 2017). The chemical reaction for the following chain is mentioned below:
10

Bacteria used for the processin bio-concrete: In the suspension state they are added to the
concretethe concrete mix is added with the bacteria in suspension state. It The concrete is
basically alkaline in nature. It is due to this reason that There aresome special qualities must be
possessed by the which the bacteria. must poses that is Tthey should be capable of surviving into
handle the extreme environmental conditions. This implies that they should withstand , survive
in the dry state and must survive in such alkaline nature. If anaerobic bacteria's are used for the
process there is increase in the compressive strength 30 times., in this Shewanella are added.
When aerobic process is used then bacteria is to be used, then's like Bacillus pasteurii, family
bacteria are used. In these following name are mentioned Bacillus sphaericus, Bacillus cohnii
Escherichia coli, Bacillus subtilis, etc. are added to the concrete.
2.3 Advantages and disadvantages of self- healing methods
There are various advantages and disadvantages of this process. Through the bacteria
spores insertion in the agamete, the healing process can be started. Moreover, it is a more
environmentally friendly method as it does not not pollutecause any pollution. Along with this,
the process is based on use of advanced and innovative methods of utilizingusing the micro-
organisms and the biological processes in healing procedure of concrete. They can easily be
present for the longer duration in the dry state (up to 50 years). This method provides more
viability and reduces the concern over the issue (Šavija and et. al., 2016). In order to maintain the
longevity of the bacteria, they use porous expanded clay particles are used while preparing the
solution for the concrete. This makes the fixed movement of the bacteria which effectively
makes the longer life expectancy of them inside the concrete. The biological based is method can
also be used to fill thosee gaps which have larger size and width. It is the easiest treatment which
can be provided to the civil process and has lowest maintenance cost (Gilabert, and et. al., 2017,
11

Seifan, Samani and Berenjian, 2016). The self-healing process using bio- concrete is more
effective and efficient and has great resistance to freeze-thaw attacks. It also reduces the chances
of corrosion.
However, there are certain disadvantages ofto this methods as it is little complex and, costly. and
Eembedding the micro-organisms can prove to be alittle difficult task. Bio- concrete is costly as
compared to conventional concrete. Further, the bacteria that are added to grow in concrete are
not considered good for human health. Moreover, calcite preparation involves investigations
which may prove to be costly. Though there are other methods which can be used in comparison
to the microorganisms such as Intrinsic and Chemical Based self-healing methods can be used to
recover the cracks generated. There are no details mentioned in the codes or standards that at
what amount or quantity these bacteria's must be added (Van Belleghemand et. al., 2016). There
is hike in the cost of the normal concrete. There is requirement of y require special environment
for making the precipitate. They affect the human health as well as atmosphere. Though there are
other methods which can be used in comparison to the microorganisms such as Intrinsic and
Chemical Based self-healing methods, but these have certain disadvantages as well. Further,
advantages and disadvantage of the other process are mentioned in the table:
Intrinsic healing method is less complex. Also, this method does not require sequestration of
healing agent. However, its healing capacity to narrow cracks is limited. As compared to this,
chemical based self-healing method has an advantage of facilitated release of healing agents.
This method is capable of responding to multiple cracks simultaneously. Furthermore, multiple
healing of repeated damage events can be obtained by using chemical base self-healing method.
However, use of vascular system in this method requires difficult installation of vascular network
and concrete casting. This method has limited healing capacity. When capsule based procedure is
used, it may be a matter of concerned if appropriate bind is not formed between capsule and
matrix.
12

Importance of the
13
Illustration 3: Difference between the different processes

Chapter 3-Self-Healing concrete- Mechanism and advances.
3.1 Role of self-healing concrete
There is various importance of it in civil construction, road making, as well as for building the
bridges. Moreover, it Self-healing concrete plays an important role in solving the problems of
concrete structures that sometimes deteriorate much before their service life. during the time of
the rainy season as direct repair can be made. Many countries face the challenges of the changing
environment. They have concerns regarding the infrastructures that develop and cracks due to
different weather conditions over time.are generated in them. Self healing concrete can act as a
significant solution for preventing serious damages to buildings that are caused due to
appearance of cracksThrough this methods, it can be prevented. Moreover, it is helpful for the
developing countries as their civil structure can be maintained for the longer duration . It
increases the strength and flexibility of the concrete and reduces the gaps or cracks in them (Van
Tittelboom and et. al., 2016). Along with this, it improves the tensile strength and compressive
strength of concrete.
Moreover, there has been an increasing demand for buildings and infrastructures owing to the
rapid growth in world population and booming economies. This also implies that adequate steps
need to be taken for ensuring proper maintenance of these structures. Furthermore, premature
failure of concrete structures causes huge financial losses. Self healing concrete can help in
damage prevention thus avoiding the situation of damage control. It will help in preventing
further widening of cracks thus assisting in averting the danger of deterioration of buildings and
other structures.
2.3.2 Mechanism and application of self-healing concrete.
The mechanism byperformed by which self-healing concrete works in self-healing varies
depending upon the repair agent that is present in the mix. The process of repair can mechanism
will be considered as self-healing only ifwhen there iswill be no human intervention. There are
different methods of self-healing of concrete are investigated by different professionals. These
mechanisms can be divided into three categories and they are intrinsic, chemical and biological.
Concrete can be healed by using its auto-genesis capacity of the dried cement that is present in
the mixture. Depending uponWith respect to this property of concrete, when water molecules
14

come into the contact, then rehydration process taookes place. In this process, CO2 reacts with
ions of Ca and form the crystals of calcium carbonate. But there is a limitation of this method as
they can only heal the small cracks present in the structure.
This mechanism was first observed in water retaining structures. Besides this, a systematic study
on the self-sealing was made by (Van Tittelboom and et.al, 2016), which reflects four different
processes which help in the healing of concrete and they are dissolution, deposition and
crystallization; physical clogging; continuing hydration and swelling of cement mix.
Furthermore, (Perez and et.al, (2015) observed the cracks in the bridges and evaluated that
concrete performs self-healing as some specimens are exposed to the freeze-thaw cycles. To
provide support to the statement, because of possession of these features, concrete is a material
with a lot of forgiveness. The reaction followed under this mechanism is:
Co2 + H2O+ Ca = CaCo3+ H2.
Nevertheless, a number of studies have been made to gain better understanding on this.
Improvising this method, there is some advances present which determines the self-healing of
concrete. The major among them is Crack width control in which a new material, ECC-
engineering cementitious composites are used to provide better support to the traditional auto-
genesis method of healing.
15
Figure 3: Mechanism of healing process
Illustration 4: Mechanism of healing process
Sources: Goyal, 2015

The image depicts the mechanism of healing process that taken place in concrete when a crack
develops. The first part shows the crack that has developed in the concrete. The second part
shows a version of calcite material that fills the crack. Thus, concrete is able to heal itself.
3.3 Advancements associated with self-healing concrete
A number of studies have been made to gain better understanding on this. Improvising this
method, some advances have been made which determine the self-healing method of concrete.
The major among them is Crack width control in which a new material, ECC- engineering
cementitious composites are used to provide better support to the traditional auto-genesis method
of healing.
16

Figure 4: Self healing mechanism (PVA engineered cementitious composite)
(Source: Yu and et.al., 2010)
The above image shows microstructure of self-healing phenomenon in PVA (Poly vinyl alcohol)
engineered cementitious composite. The self-healing sequence shows that large crystal structures
of carbonate have fully occupied a crack of 100 μm.
17

Previously, the fiber used was polythene was used in self-healing concrete but nowadays, it has
been replaced with Polyvinyl Alcohol took the place of that fiber. Moreover, it was investigated
by many researchers that water supply to the concrete helps in the further hydration of the un-
reacted cement (Huang and et. al., 2016, Roig-Flores, and et. al., 2016, Feiteira, and et. al.,
2017). In addition to this, by adding microfibres, the process of healing can be amplified.
Besides this, Sangadji, Wiktor and Schlangen, (2017) explained the importance of hydrogels or
super-absorbent polymers (SAP) as these are the products which can absorb large quantity of
water. Further, these molecules then retain the absorbed water into the structure without any
dissolution. The swelling occurred due to the absorption seals the crack partly, which later
healsed completely by desorption of SAP. This which provides the fluid to the surrounding
structure for internal curing. Afterwards, rehydration takes place and the precipitation of calcium
carbonate takes place. Thus, cracks may close completely with this method has the capability to
repair the cracks completely. As per the views of (Irico and et.al,( 2017), autonomous self-
healing property of method possessed by the concrete is the most effective. In contrary to the
auto-genesis mechanism which is inherent feature of the concrete, autonomous method is a
purposely designed self-healing mechanism.
(Van Tittelboom and et.al, (2015) suggested the best way to study the self-healing mechanism of
this autonomous type of self-healingmethod. It involvesis dispersing the capsules filled with a
cementite or synthetic healing agent. These agents absorb the water and result in healing process
to happen. In order to recover the limitation of penetration of water into a crack from external
sources (Schlangen and Sangadji, S., 2013) suggested that with the help of water-saturated
porous particles, this issue can be resolved. According to (Talaiekhozan, and et.al, 2014), cracks
can be healed by using calcium carbonate precipitating micro-organisms. In this, the
precipitation of CaCo3 will take place which will destroy the bacterial cell by providing a coat of
calcium carbonate. This is a bio-based self healing method. It should be noted that the bacteria
that will be used in this process should be effective enough to heal the cracks for the long period
of time. In order to increase the durability of these bacteria (Dong, and et.al, 2015) proposed the
method of encapsulation. In this method, bacteria are implemented in the mix with an outer
covering that helps them in sustaining in the concrete matrix for a long span of time to achieve
18

the effectiveness of the mechanism. The use of the different kinds of bacteria works in the
various areas which can help to increase the process.
The commonly used bacteria in the self-healing process are anaerobic, aerobic. Further,
few of them are Bacillus sphaericus, Escherichia coli, Bacillus subtilis, etc. Moreover, (Van
Belleghem and et. al., 2016) presented a detailed report on the different bacteria based methods
that can be used governing calcium carbonate precipitation. A deep research on this helps them
in concluding four major factors that govern the CaCo3 are pH, the concentration of calcium,
dissolved inorganic carbon concentration, and nucleation sites. In order to prove this method
effective a three point bending test is performed.
19
Illustration 5: Bacillus sphaericus under microscope
Sources: Goyal, 2015

In contrary to this, Perez and et.al, (2015) put his views and claimed that the most
effective and simple mechanism of self-healing is fly-ash and blast-furnace slag concrete. It is
because of the low hydration degree of the slag and particles of fly ash. In this mechanism, the
alkali activators are the ones who heal the cracks and regain the water impermeability and
strength. A different approach of self-healing of concrete is proposed by Tziviloglou and et.al,
(2016), through a different route and that is the metabolic conversion of the nutrients. In contrary
to these methods, chemical mechanism of self-healing was also observed effectual. The main
chemical based methods are the adhesive agents that are stored in capsules. These capsules help
in connecting two surfaces of a crack together. The commonly used adhesive agents for this
method are epoxy, methylmethacrylate, cyanoacrylate, etc. According to Van Belleghem, and
et.al, (2016), vascular based self-healing method employs the concept of bleeding via a network
of capillaries or hollow channels. This method can be implemented in two type either active or
passive. Active is the one in which, no human intervention is required, the capillaries of the
structure enable this procedure. Whereas passive self-healing is attempted by actuating external
hollow channels (Lucas, and et. al., 2016).
In various fields, there is important application of self-healing concrete. It has provided a
greater solution to the civil engineers who are working in the extreme climatic conditions.
Moreover, its application can be used to improve the different structural system by the use of
modern technologies. There is certain limitation, but its application can be increased in future.
Field application in CRUZSACHA CANAL, ECUADOR
20
Illustration 6: Self-healing process
Sources: Goyal, 2015

In Ecaudor, irrigation channels are there for the supply of water for the drinking and
farming purpose. Due to changing the environment and high turbulent pressure, there are cracks
generated in the canal which causes leakage and water penetration. These impact in the reduced
water supply at the utilization areas such as farming.
Some of the researchers added bacteria and calcium lactate in the Cruzsacha canal. They
used two approaches to reduce the impact of cracks. To develop the self-healing they used the
capsule and natural fibers. The bacteria were saved from the extreme environment through the
capsule. Psychrophilic bacteria's were used in the process to prevent the impact (Seifan, Samani
and Berenjian, 2016). When the alkalinity level increased the bacteria's got activated and within
100 days they repaired the 0.80mm cracks. After the process was completed the bacteria's again
went to the inactive position. The cost which included in the process was based only on the
bacteria's and employees and community training. The price of 1 kg of self-healing bacteria's
was € 2.11. The other cost was totally based on the employee training. Though the initial cost for
the product was little expensive it provides long term benefits. It increased the durability and
strength of the canal which benefited the farmers. Later there was very less cost in maintenance
and repairs of the canal.
Montrose Bridge in Scotland
There was repeatedly cost invested for the maintenance and repair of the bridge which
accounted for £7.5m. Using the methods they can effectively save more than 60 to 80 million
euros which government was investing for the repair annually. Moreover, it was found that life
expectancy of the bridge has expanded by 50%. The bridge that can withstand for 12 years, now
can have the ability to survive more than 18 years that too without the maintenance and repair
cost (Tziviloglou. and et. al., 2016). The Dutch government has recognized that the method is 10
times more cost effective and plays the significant role in the increasing the lifespan and
reducing cost invested in the repairs.
Further, the application based on the Architectural Designs and Structures are mentioned
down below. Building and architecture play major role in the construction. Further, concrete is
the only suitable for construction of such big size buildings (Al-Ansari, and et. al., 2017, Wang,
and et. al., 2017). Hence, there is a great use of the self-healing concrete in the architectural
designs. Use in the residential and public areas:
21

The life span of any building can be estimated through the size and their functioning. For
the construction of the building, concrete is mainly used as the foundation so that structure
lifespan and strength can be maintained. There is the vast use of the self-healing concrete in the
medium size building as they can increase their lifespan and strength by using these process. It
provides more function, flexibility, and effectiveness which reduces the risk of remodeling and
demolition of the services. This will also help in reducing the CO2 emission which increases
when construction process is carried out. However, for the larger building, bridges and roads as
due to heavy load, climatic condition and other factors they get more harm. It can significantly
reduce the cost of maintenance and will effectively increase the safety as well as the strength of
the structure when self-healing concrete is used (Gilabert and et. al., 2017). Along with this,
there will be also enhancement in the durability of the structures.
2.4 Effectiveness of the self-healing process
In terms of the effectiveness, there are various advantages of the self-healing concrete.
However, there is the restriction in the process as the healing can only possible to certain limit
(De Nardi and et. al., 2017). Further, its implementation its limitation for being applied for the
longer period and strength recovery are very less. These can be changed if capsules and vascular
system are used in the traditional concrete.
2.4.1 Self-healing Attributes.
The process is majorly based on the system property and not on the material composition.
So the process has the disadvantage that it cannot be applied to the universal system (Applied at
the all kinds of application). Nevertheless, there are chances that they can be implemented to
recover such losses. Scientist and researchers are identifying the areas which can help them to
make the relevant self-healing concrete which can accomplish all the features required for the
self-repair. They have to spend a lot of research on such topic and identified some of the
techniques related to it. If such technologies are implemented or identified than the system of
self-healing can become more effective and efficacious (Kanellopoulos, and et. al., 2017).
Along with this, using the self-healing concrete there are certain issues to the health of
the humans and environment. So the process must be designed in such as ways that these factors
can be eliminated and it can satisfactorily accomplish the essential properties (Feiteira and et. al.,
2017). The major requirement in the stages of the self-healing concrete is self-reflective and
22

comprise of the self-detecting ability. The system must work similar to the human body and must
apply its healing process whenever such indications are seen. Whenever there is demand the
system must initiate the process and should fulfill the gap or crack. Once their process is
completed it should again come back to its original process. For this embedded configuration
mechanism is required. The self-healing process must be more compatible and reliable so that
the structural performance or bonding does not get affected. It must be assured that it should
perform its duty in more specific and functional ways. Finally, if the concrete must be able to
detect the strength of the construction of its own.
2.4.2 Robustness Criteria
There are 6 criteria which are used to evaluate the robustness of the process. These are: Shelf Life: In the civil construction, as they services last for the 100 years at least so at
any duration there can be cracks in the concrete (Wang, and et. al., 2016). So the process
must serve their assigned time period and should preserve their long shelf life. Pervasiveness: In the civil structure, there are various ways through which cracks can be
generated. This can be due to load and or complexity in the structure. So as per the
location and orientation they must be recovered and should be self-predicted (Al-Ansari
and et. al., 2017). It should not be based on the orientation, however, the structural
integrity must be maintained. Quality: For any type of the self-healing concrete, its effectiveness can be governed
through its ability to regain. The ability to mechanical properties, permeability and
diffusivity, of the crack, developed. Thus, for maintaining the quality, the healing
mechanism must be effective and sealing/crack filling should be filled as soon as cracks
are identified. Moreover, it must develop the mechanical strength which can keep the
civil structure in its place.
 Reliability: When self-healing concrete is applied should perform consistently. If there is
lack of consistency then the Further, the outcomes must be accurate and should be based
on measurement and specification which were used to make the self-healing concrete. As
declared by Sangadji and et. al., (2017), if there is the lack of the consistency in the
solution then there is very minimum relatability of using that mechanism.
23

 Versatility: Versatility can be defined as the ability to perform different function or
activities. As stated by Gruyaert and et. al., (2016) self-healing concrete have effective
versatility as the advancement to recover and regain must be fulfilled as soon as the
cracks are identified. Moreover, they must not get affected by any other factors and
should retain its property for the longer duration.
 Repeatability: As the time duration will be there the civil structure will lose its strength.
Hence, cracks will be developed as the time will pass and due to continuous loading
situation (Mignon and et. al., 2017). Therefore repeatability of such concrete can be
maintained through its multiple properties. The concrete must be able to self-repair the
cracks, must identify it and should regain to its previous position when its use is not
there.
2.4.3 Robustness in its approaches
For the following section, the effectiveness of the self-healing process is evaluated on the
biological process, the other approaches are not discussed as they are not described above. In the
biological process, the bacteria are added and concrete effectiveness is observed for several
periods of time.
In terms of the criteria, in the mentioned process the expanded clay particles are used.
The spores developed after applying these can be uniformly distributed in the concrete matrix.
When discussing about the quality, the healing properties are to the excellent while mechanical
strength is very low. Reliability and versatility, there is still no research made. Repeatable, there
are sufficient data not available.
As per the Sharma and et. al., (2017), the versatility and reliability were seen in the other
approaches, it was very less found in the Biological process. Further, its effectiveness was also
less.
2.5 Cost-Benefit Analysis and sustainability of self-healing concrete
There is need of the maintenance, durability, and self-repair in the traditional concrete
which can adversely affect the civil structure. Further, they require the repair work after every
specified time period. Besides this, adding the self-healing concrete, durability and strength can
be increased. Though it has higher initial cost when long term stability and economic utility are
24

seen it is more effective methods. There is also a reduction in the cost of maintenance and repair.
Many researchers such as Khitab and et. al., (2016), have identified that it would cost them €
31.65 per m3, however, the cost for the maintenance and repair is very large and time-consuming.
As mentioned in the above study that the cost of the reconstructing and re-development
that are used in the other areas like the UK, US, and Asia comes to be over billions and trillions
of dollar and there is hardly cost of the self-healing concrete in comparison to it (Han, and Xing,
2016). Along with this, the sustainability of the report can be gained through the aspects which
are mentioned below:
Safety: As there with the help of the self-healing concrete the general safety of the structure
raises. In addition to this, it may be noted that healing procedure helps concrete in gaining
around 25% more stability.
Cost: Self-healing concrete helps in elimination extra cost associated with the maintenance of the
structure (Abbas, Nehdi and Saleem, 2016). Further, the durability of this type of concrete
structure also makes it a cost-efficient option to prefer.
Durability: From the various researchers that are been conducted on the durability of the SHS, it
was observed that bacteria assists SHS are more durable than concrete.
Availability: SHS lacks in this factor. Unlike regular concrete, they are less available and are not
much wider. The limitation of this section is the obstacles that are faced in its production and a
number of the constituents that are added in this areas.
Effects on Architecture & Design: Whenever self-healing concrete is used in the civil
construction, engineers need to reconsider the design structure (Alghamri and et. al., 2016). For
any structure which is standing for the longer duration, architectures must consider two main
aspects in these:
(i) the expected purpose within a specific construction
(ii) The upcoming role of citified location encompassing a definite building.
Therefore, civil engineers and architectures' have one more role that they must foresee the
future demands that are required by the construction and current requirement which are
necessary for that construction. Moreover, it must be more aesthetic and significantly, having
greater flexibility construction so that its functionality can be easily changed.
25

Environmental impact: There was greater impact caused by the cement plants and when the
building is reconstructed. Further, there is more generation of the CO2 level due to such
construction. These were making more impact to the environment which can be reduced by the
application of self-healing concrete. Moreover, it reduces the resources utilization and serves as
environmentally friendly.
Strength: When the strength is discussed related to traditional concrete, there is the rise in its
level. Further, it increases to more than 25% in the level and duration for holding the structure
also increases. Moreover, the sustainability can be seen in this process as the concrete based on
the biological aspects as they are better and have the effective crack sealing process (Nosouhian
and Mostofinejad, 2016). They have the better approach to fulfill the porous and the gaps which
are generated through the cracks.
26

CHAPTER 3: RESEARCH METHODOLOGY
3.1 Introduction
The section of the report is based on the tools and techniques which are adopted and
implemented in the research for the evaluation and better understanding. Moreover, it is required
to gain knowledge related to aims and achieve answer to the question and answer. In this section,
necessary details about the research approach, design, methods and philosophy are mentioned.
Further, ethics, reliability, validity, and limitation are evaluated in the research. Data collection
and ways they were analyzed are also mentioned.
3.2 Methods, tools and techniques
For conducting any research, its approach must be clear to the researchers. In part, the
best techniques are used to carrying out the study in more general or specific way. It can enact as
the master plan were collected methods and data analysis process is mentioned. Such approaches
help to reduce the chances of mistakes and fault in their findings and process carried out. There
are two ways through which research approaches can be used in the dissertation (Rajesh and
Venugopal, 2017). These are deductive and inductive. In the present research, the approach
chosen is the inductive type were from the general to specific part has been studied. On contrast,
the deductive approach is not used as it was based on the development of the new theories and
themes. Entire focus in research was given on the self-healing concrete and their application and
their process. On the other hand, the other methods were not used because there was no
development of the themes and generalization here.
Another concept which is used in the research is the research philosophy used. It is based
on the values and belief of the researchers to carry out the outcomes of the research (Kalhori and
Bagherpour, 2017). Moreover, what application is used and thoughts are mentioned by the author
are written in this section. It should be properly identified as it is directly related to the research
aims and objectives. For any such study, there are two types of the philosophy, interpretivism,
and positivism that are used in the dissertation. The former-one is based on the belief of the
multiple realities and is dependent on the methods applied. Moreover, it helps to identify the
challenges that will be faced by the research. Generalization is not given importance in this part
and complete focus is given on the human behavior. The other philosophy is based on the belief
and values of others. For the present research, there was a use of interpreting vision which had
been undertaken to understand the role of researchers that are connected to the human belief and
27

provide details about the self-healing concrete. As the topic already contained the truth so the
other philosophy was not used.
Another concept on which research is based on is the designing of the research. It is the
blueprint of the study which is based on the accomplishment of the aims and objectives. It is
used in the dissertation so that its relatability can be increased and enhanced (Hanna, 2017).
There are different ways through which research design can be carried out. Such methods
involved descriptive, casual, exploratory etc.. The beginning is based on the description of the
subject being selected. Exploratory methods are based on the ideas and thoughts development.
In the mentioned dissertation, descriptive research design is selected where the main focus is
given on the self-healing concrete, its effectiveness, application, and sustainable development
through it. On the other hand, the other methods were not used because there was no new
research mentioned about the topic.
Research type reflects nature as well as the techniques used in the research to gain the
outcomes in an effective manner. Before starting the research, its type should be maintained so
that it can be carried in effective ways. There are two types of research, qualitative and
quantitative (Feiteira and et. al., 2017). The first one is carried out when information is present in
non-numeric form and the second is based on the when the data provided is in the numeric form.
Further, in the latter one statistical tools and techniques are engaged for analyzing the
information. Present research is based on the qualitative ways, as there were numeric values are
present. Along with this, there were themes developed on which further discussion was made.
Data from the various professional researchers are selected from the journals, articles, and books
which are effectively used and demonstrated in the research project. This was the main reason
behind considering the research type as qualitative and not as quantitative.
The last part, that is the effective data collection and its analysis. In the above literature
review, the complete details are provided about the importance of the self-healing concrete, its
cost-effectiveness and sustainability are discussed in the complete dissertation. Under this,
analysis, describing and topic evaluation is discussed in the maintained report. To understand the
self-healing concrete the main details which are provided are based on the mechanism, its
application at different areas. For the research as mentioned the secondary type of data collection
methods is used. In this details from the various authors which have published their journals
28

related to the topic are mentioned in the report. Their complete study, data analysis and graphical
methods and other details are mentioned in the reports. The entire report is based on the
secondary data, that is being published on the mentioned topic that is self-healing concrete.
Along with this, to maintain the reliability and ethics of the research its is properly cited and
professional authors are selected for the study who have gained effective outcomes in the study.
In the research, multiple research engines, process, tools, and techniques were used so that only
material related to the topic can be mentioned and studied. Journals, articles, books and other
online sites were used to access the data. Furthermore, the detail was mostly from the biological
scientific studies and technical engineering fields (mostly from the civil engineering areas).
Other than this, relevant publications that which is related to the other topic in the research such
as sustainability, cost effectiveness and mechanism were identified and mentioned in the
dissertation. Digital technologies were mostly used for gaining knowledge and details about the
application of the concrete. Online material is mostly used in the research, materials that were
easily available are used in it. Books and other articles related to this study were used in the
Literature section of the report.
Information and data were also collected from the blogs of some famous scientists who
have contributed in this study are still making progress under the current field. At the end of the
research, recommendations and conclusion are provided based on the study which author has
gained from the study of the secondary data. There are more details which needed to be explored
in this research projects for this many types of research are still going on to make this self-
healing concrete more reliable, cost-effective and sustainable to the customers. Due to this
reason, there is the certain limitation in the completing the research. There are many future
scopes which can be seen in this areas and it can be larger as well as the major part in the civil
construction.
In order to complete the following research project, there was the use of the many journal
papers, books and articles were used. For making the other person gain more information about
the topic some of the key terms were identified which supported the researchers to gain the
details about the topic that is self-healing concrete, its application, cost-effectiveness, and
sustainability. Other than, this the main details which were accessed was only limited to the
biological process. There is two other process than biological, they are intrinsic and chemical
which is not discussed in the present research. Details like advantages and disadvantages are
29

only mentioned about them. Main key words that were search in this research was self-healing
concrete, the material used in building, biological self-healing, cracks, mechanism, repair-
system, construction and design, architecture.
30

Chapter 4: Data Analysis
4.1 Introduction
After the research methodologies, the next section of the research project is data analysis. It is the process
in which the data access is investigated and logical reasoning is accessed in an effective manner. Along with this, it
is required to evaluate the aims and objectives of the report. The part of the chapter contains the details where
information gathering, analysing so that interpretation can be done. All this is completed so that conclusion and
recommendation can be made on the basis of discussion. The subdivision in the report comprises of the data analysis
for 'Self-healing concrete and its application. For analysing the data, secondary data collection method has been used
and outcomes are made in the thematic basis.
4.2 Thematic analysis
Theme 1: Self-healing concrete help in recovering the cracks and maintaining the strength level.
Findings: Being one of the most durable building material, self-healing concrete is famously known for its several
healing properties with a foremost role in improving the cracks in the buildings. This is basically to maintain the
strengthening level of the building that is built using such effective material. Considering the same, self-healing
concrete is itself known as a living concrete that tends to repair the cracks themselves. It is on considering the
secondary sources of data, one can easily look into the healing properties of self-healing concrete where it is widely
used in construction work. Despite being a very old age theory used since Classical times of Roman, it is more
popular these days. It is however preferred to be the outcome of an intense research carried out by a well-known
microbiologist named Hendrik Jonker (Šavija, and et. al., 2016).
It is mainly in context of the most common material concrete that is largely used all over the globe.
However, it does not provide any sustaining results and leads to crack and worsen at the end. It is therefore in order
to find out sustainable outcomes, a new generation of self-healing concrete has taken place where it presented as a
solution to such unsupportive consequences. This, in turn, reflected an important agenda of resolving the aforesaid
issue where there existed a prime need of inventing such effective substance that in turn results in a better
application of concrete. This, in turn, resulted in an active existence of self-healing concrete made up by using
various bacterial contents in it. From the biological perspective, it is proven to be one of the friendliest approaches
where self-concrete is essentially made up of an effective material called bio-concrete.
Theme 2: Elements that can increase the mechanism and reduce its ill-impact on humans.
Findings: It is mainly in context of an increased mechanism of self-concrete where it is created using mineral
producing bacteria that is in turn evident to assist in fixing the minute cracks in the building. It is in accordance with
the studies based on the secondary sources of data were self-concrete formula is apparent to resolve the issues
existing from the corrosion of concrete structures that are supposed to sustain for a longer time period. It is mainly
with reference to a superior use of concrete in the field of construction where deterioration of structures before their
guaranteed service life is proving to be an intense issue. This is also on considering the fact where concrete is
31

extensively used from the establishment of buildings to the structuring of underground parking lots to the formation
of bridges.
It is therefore to maintain a sustainable position of these construction work; use of self-concrete healing is
known to play a major role. This is due to yet another considerate fact where a minute ignorance can also lead to
worsening the entire situation by directly affecting the lives of many people. It is therefore important to such healing
agent that in turn provides an assurance of sustainability to a greater period of time. It is thus on comparing the
traditional way of construction where the concrete used in that process leads to crack when exposed to strain or
pressure. It is however on considering the fact related to the usage of self-concrete healing that is also exposed to
several numbers of ill impacts on the human.
It is a foremost concern of bearing the cost related to an effective use of self-concrete healing. Herein,
studies have revealed the reason behind an increasing cost of self-healing concrete where it is basically due to a
raised price of calcium lactate. Apart from this, the use of bio concrete together has some leading ill effects on the
physical and psychological well-being of individuals. It is mainly in context of the use of various bacterial contents
that could lead to the release of ureases. This, in turn, can lead to the evolution of a disease called Proteus mirabilis.
Though, there exist some non-harmful microorganisms that can be used to reduce such ill impact of bio concrete on
humans. This involves the use of Bacillus pasteurise as a proteolytic that is not harmful in comparison to the
previously specified bacteria. Being a non-pathogenic bacterium, it is widely used in the formation of self-healing
concrete. However, there still exists a matter of concern regarding its expensive price range that often restricts the
individuals to use it on an often basis. Instead, it is important for the construction industry to take a serious
consideration about its effective use for saving the future concern of costs in repairing and restoration of bridges,
buildings and parking lots, etc (Pamulapati, and et. al., 2017).
Theme 3: Possible threats from such methods to the civil structures and environment.
Findings: From the analysis of the overall study it has been gained that there are certain negative outcomes of the
process. 20% of the volume of the concrete comprises of the clay pellets that grasp the SH agent. In this percentage,
there is more composition of the gravel. Hence, clay acts act as the weakening agent and reduces the compressive
strength by 25%. Though the compressive strength is hardly required for many structures when there is special
application then such there will be higher risk. There is a problem related to the addition of the materials or
constituents in the self-healing concrete. It should be more specific or otherwise other problems can be generated.
Moreover, such factors can not be ignored. As per the research of Henk M. Jonkers & Erik Schlangen, they have
identified and developed study which was based on identifying the strength level.
Along with this, it can be seen that the cost of the traditional concrete is just the half of the SHC. The
current price of the self-healing concrete can be up to €160 euros per cubic meter. As there are more advantages of
it, however, people like to choose the most cost effective methods. Nevertheless, the areas where safety is majorly
required SHC can be used. For example, in the construction of the civil structure such as bridges, highways, tunnel
linings and marine structures it can be used as in these type of the structural safety is majorly required. Moreover,
these are the areas having limited access areas for the repairing and maintenance system. Adding the self-healing
32

concrete in such areas regardless of the cost must be considered. Other than this, the cost specified can be reduced
but that will require larger production.
Among the three mentioned methods it was identified that biological based self-healing methods have very
less ill-impact on the environment and humans. Using the micro-organism can help to prevent the damage and it is
pollution free approach (Khaliq and Ehsan, 2016). They are having the greater life span (50 years) and ability to
identify the cracks or damages by themselves. Along with this, they can easily exist in dry concrete for the longer
period. When reconstruction of the civil structure is taken account, there is more CO2 release, as well as resources,
are more utilized. There is further investigation going on this process to reduce its impact on the humans and
environment. Though in the biological process, there is less strong it is found to be more versatile than the other two
methods. There is another important thing required for the biological process, they require special climatic
conditions for their survival which can impact to the civil construction.
Theme 4: Effectiveness in using the self-healing concrete
Findings: From the analysis of overall study it has been gained that there are greater advantages of using the self-
healing concrete in comparison to the traditional concrete. The effectiveness of the mechanism can be seen through
the robustness in the procedures. Many researchers have acknowledged that there are greater advantages of using the
self-healing concrete for the industrial applications. Here the discussion is mainly concentrated on the self-healing
process through the biological method. The criteria used was using the methods in the in-expanded clay particles.
They have the life expectancy of 6 months and can be easily distributed uniformly on the surface. Its reliability is
still to be studied by the scientists. However, the use of different types of bacteria's can helps the structure to survive
in different environmental conditions. Strength is increased and the level of transportation also increases.
The examination was held in the different conditions such as application areas, environment and place and
effectiveness was evaluated. As mentioned, the positive outcomes have been studied by the researchers. Along with
this, from the study of the articles related to using of self-healing concrete in the UK, Scotland, and Ecuador it was
found that methods have provided the greater advantages. The cost they were using for repair, maintenance and
reconstruction were saved and can be used in some other areas. Further, the amount that was saved accounted more
than 100 Billion dollars. Though as per the findings, the initial cost of the concrete was double than the traditional if
the long term investment is seen then using the self-healing concrete is the best methods. The test results from the
study Bhattacharyya, Pelletier and Bose has shown increment in strength and other features in the self-healing
concrete. The only factors that were to be maintained where the environmental conditions and areas where the
solution has been applied. Temperature, thickness, pH level and crack size are the main aspects that need to be
focused on the application of this areas.
As per this research, in the past 10 years, several improvements have been made in self-healing concrete's
effectiveness. Earlier, this type of concrete was used in the small structures with the defined crack shapes and sizes.
The efficiency should be investigated. This is done after the exposure of capsules whenever the crack occurs and the
casting process starts by those capsules. Non-destructive testing can be done by using acoustic emission analysis or
33

X-ray radiography. They are used to finding out the survivability of the capsules when they are mixed in the
concrete. These methods are also done to get to know about the braking ability of the capsules whenever the crack is
formed. The evaluation was done by performing water permeability test. As soon as the crack occurs, the capsules
get activated. They start expanding and replacing the other particles with the bacteria to heal the crack. Such type of
techniques will able to identify the effectiveness of self-healing concrete.
Theme 5: Cost-effectiveness and sustainability can be maintained in such process.
Findings: The factors that highly contributes in the reliance of self-healing concrete are its cost-effectiveness and
sustainability. It has been evaluated from the secondary data collection that irrespective of the high production cost,
the use of SHC in infrastructure is an effective method. It is because of its self-healing properties which help in
diminishing the extra charges associated with the maintenance. The examination conducted on the strength of the
infrastructure prepared from self-healing concrete was observed up to the mark that reveals the durability of the
material. The deterioration of the traditional concrete structures causes economic consequences such as maintenance
and if more damage is there it leads to reconstruction. In contrary to this, the auto-healing capability of SHC gives
economic advantages.
Besides this, the scrutiny on the constituents such as bacteria based strength assists in obtaining positive
outcomes which reflect the advantages of using self-healing concrete over traditional concrete. By making the
analysis of the information gained through secondary sources it has been determined that SHC is a cost-effective and
sustainable element which is more beneficial than the normal concrete. In addition to its cost-effective, the research
also helped in analyzing the sustainability of SHC in the different context. In contrary to this, using SHC in
construction can reduce these environmental impacts. The use of ordinary concrete releases CO2 which becomes
hazardous after enhancing global warming. However, the auto-healing property of SHC makes it a "smart material"
and using SHC in the construction of infrastructure which possesses the quality of durability, there will be less
emission of CO2 and hence, less damage to the environment will occur.
In contrary to these points, the investigation on the self-healing concrete reveals that there are some
problems in its availability which somewhere impacts upon its use till some extent. By making an analysis of data it
is observed that the production cost of SHC was obtained comparatively higher which impacts upon its productivity.
In addition to this, there are some environmental factors which restrict the growth of bacteria which results in failure
of structures based on SHC. However, the success factor of this material lies in its numerous qualities that are being
accessed while constructing structures.
Theme 6: Verification of SH ability on fabricated SHC.
Findings: Self-healing is the terms used in the construction industry where it is related to the concrete source for
constructing buildings. Under these several kinds of methods are included and the present study is based on
biological procedure. In the current theme, experimental method is considered which is highly supportive for
fabricating the self-healing concrete. It is one of the significant methods through which procedure of self-healing can
34

be completed in the proper direction. With the help of biological process, the engineers become more capable in
terms of close self-healing and construct the buildings. Those engineers who are working in the industry of
construction are trying in order to utilize bio-mimicry in which various mechanisms included. Along with this, they
able to develop concrete of bio-based with the help of selected process in self-healing. It is one of the highly
effective methods because it supports to contractors in terms of completing the approach of self-healing with
environment-friendly.
In addition to this, with the self-healing, all the composites are included which rely on the cementitious and
this process of involving known as pre-mixed products. The below-mentioned tables show that up to which extent
the self-healing fabricated is proper and appropriate.
Illustration 7: Mix-proportions of cementitious composite materials
based on the self-healing design
Illustration 8: Mixing proportion of concrete
Illustration 9: Mix-proportions of binder
Theme 7: Potential usage of the biological self-healing concrete.
35

Findings: There are many advantages which can be seen in using the biological self-healing concrete rather than
choosing the intrinsic and chemical methods. From the information that has been gathered from secondary sources,
it can be examined that the biological SHC are effective to a greater extent. It has been scrutinized that there is some
adverse effect on the environment of using chemical methods. In contrary to this, the biological processes are
degradable and does not cause any harm to the ecology which reveals the environmental sustainability of using
biological self-healing concrete. Further, the structures become the victim of chemical methods due to the reaction
that directly impacts upon their strength.
The secondary data that has been collected by secondary sources it can be analyzed that biological concrete
mix validates flexural and compressive strength. In addition to this, some claim was made that polymers are better
than that of the bacterial concrete, however, the further examination explained that these polymers release some
liquid monomers which decrease the shelf life of such type of concrete.
With the help of the secondary sources, it has been evaluated that the biological self-healing concrete is
more durable and provide more strength to the infrastructure. It is due to its inert nature and capsule diffusion which
leads to zero possible chemical change and thus, no deterioration of the construction will take place. By making an
examination on the permeability of conventional and biological concrete, it has been analyzed that the structure that
has bacteria based concrete have the low permeability which makes it more durable than the formulaic concrete
infrastructures. This type of concrete mix is potentially used because it offers a high level of resistance to the freeze-
thaw attacks that reduce the chances of corrosion in reinforcement.
It has been examined from the secondary sources that the use of these concrete structures should be limited
to some extent as there are some adverse effects of these bacteria that are used in such infrastructures on human
health and on atmosphere too. By making the analysis from the data that has been collected from the alternative
sources, the use of such reinforcement should be prevented in health care homes and schools. This factor results in
comparatively higher rates of this concrete which can not be afforded by everyone and this is also a limitation of its
use. Some other factor that limits its use is the weather and the environmental conditions as bacteria are living
organism and their sprouting are suitable in some conditions. Despite this element, biological SHC is significant in
context to the construction field.
Theme 8: Major difference between the self-healing concrete and traditional concrete.
Findings: By making analysis on the secondary sources it was gained that the traditional concrete lacks in pursuing
environmental sustainability as it releases CO2 in surrounding that creates hazardous problems like green house
effect and global warming, in contrary to this, it has been examined that SHC uses biological constituents for
healing and thus, it does not affect the environment by emitting CO2. Further, the inert nature of biological
based concrete structure possesses no or less deterioration as compared to the traditional concrete
which is highly reactive. The diffusion of bacteria in form of capsules makes the reinforcement
noble.
36

From the examination that has been done with the help of secondary information which is
collected from secondary sources, it has been examined that the biggest advantage of using SHC
over the conventional concrete is that it is cost-effective. The permeability segment of the
concrete, it has been analyzed that SHC being a less permeable material restricts the entry of
foreign substances that increase the strength and thus, the durability of the structure. Whereas,
the traditional concrete is more permeable thus there are high chances of corrosion in the
reinforcement based on this mix. In chemical SHC, the capsules containing the calcium mix fill
the cracks that occur due to the pressure of water, unlike the tradition concrete structure that can
not withstand in such situation. Thus, the SHC is a revolutionary tool in the construction of
dams, bridges and boat hulls.
37

CHAPTER – 5 CONCLUSION AND RECOMMENDATION
5.1 Conclusion
From the above study, the conclusion can be carried out on the basis of different objectives. The
dissertation about the self-healing concrete, its application and sustainability have been successfully studied and
positive outcomes have been gained. There is wide application of the SHC in the civil structure and in development
of the traditional concrete buildings. The researchers have tried to accomplish all the objectives mentioned in the
study from the investigation. It has been carried out in more effective and efficacious ways so that recommendation
can be made on the study. Ample amount of information has been collected and sourced in the dissertation so that
study on the self-healing concrete can be made.
Objective: 1 To study the importance of self-healing concrete.
From the above study, it can be concluded that self-healing concrete has changed the ways civil
construction were made. There is greater scope in the application and other industries. It has been inferred that it
saves a lot of money that is being invested in the repair and maintenance. Further, those areas where cracks having
larger gaps people use to make reconstruction which cost them as well as to the environment. Every year, UK, US,
and many other countries were spending more than 100 billion dollars for the reconstruction, repair and
maintenance. When it was applied in the areas, Ecuador, Scotland, and UK, effective outcomes can be seen. After
gaining from the secondary information it has been accessed that there is the increase in the strength, flexibility and
time durability of the concrete areas. Other than this, it has been seen that they can identify the cracks themselves,
repair them and come back to its original position. All this task are completed by them without the involvement of
the humans. These are added at the during the making of the concrete and then life durability of the concrete
increased to double. It has been determined that the application of the self-healing has proved to be advantageous for
the people that have applied it in practice.
Objective: 2 To understand the mechanism and application of self-healing concrete.
From the present report is the mechanism has been effectively evaluated, here details about the biological
process, chemical, intrinsic methods have been mentioned. Proper application areas and the environment or factors
that are required in the research are mentioned in it. Further, it can be evaluated that the process is applied in the
way they are mentioned then they can be effectively applied on the cracks. The process will be faster and the
affected areas can be recovered within few weeks. They have adopted the methods in their civil construction where
danger from the cracks can be more. The challenges to its use in only that, it requires high initial cost and specific
standards of elements added. The mechanisms that are available in the current studies are mentioned but it is also
minimum there will be further study and researchers will be organized in the process.
Objective: 3 To analyze the applications of self-healing concrete in future of civil engineering.
From the application areas, it can be concluded that there is the vast application of it. However, people
prefer the traditional concrete as it is less expensive. However, the government of the Scotland and UK have
recognized the advantages of the self-healing concrete. Further, there are more advantages compared to the
38

disadvantage of the self-healing concrete. People in different countries have started using it and are getting
themselves protected from the repair and maintenance cost. There is the vast scope of the self-healing concrete in the
future of civil engineering.
Objective: 4 To recommend ways by which these methods can become cost-effective and sustainable in future
It has been explored from the study that there stated methods is more cost-effective and sustainable in the
present conditions. There will be more scope in the future for the same. New Research's, ways and elements are
searched by the scientists so that data improvement and advancement both can be implemented in the study.
Moreover, it has been concluded that if the price of the concrete is less then it will be more utilized and preferred.
Further, if the bacteria have increased the process will also hike up and efficiency will also boost. However, research
on such areas and focus on the environmental and climatic conditions are still to be made. Life expansion of the
concrete can be seen and they the ways they can recover themselves makes them more sustainable for the future
application.
5.3 Recommendations
There are several recommendations that can be made on the self-healing concrete, its cost-effectiveness,
and sustainability. These are made so that further development can be made or implemented by the researchers that
are carried out on the same topics. Moreover, the effectiveness of the process can be increased in more significant
manner. It can be suggested from the aim that civil constructions require these type of technologies so that they can
reduce the extra cost that they are adding in the repair and maintenance of the buildings. Moreover, in the countries
like the UK, US and part of Asia where the people are considering the reconstruction as beneficial should implement
self-healing concrete. This can be done through popularizing the details regarding the benefits which are gained by
applying or using the self-healing concrete.
These countries can save billions of money as well as can preserve the environment. When construction
process of new building is made, there is the release of more CO2 in the environment which causes harm to humans
and nature. These can be stopped through the application of the self-healing concrete. As the cost of the product is
more so government must support and should promote the use of such technologies. Other than this, the issues that
are being faced in these areas is the standards and ways the constituents must be added to the solution. It has been
found that to increase the effectiveness and sustainability of the self-healing concrete, researchers are making
progress.
It is suggested that in order to improve the effectiveness and to reduce the cost other similar elements can
be used in the process. Further, the technology development is more required in this areas of the research where the
main focus must be made on the application areas, climatic conditions, and constituents. If cost and its application
areas are identified then more people will adopt this technology for their civil construction.
39

REFERENCES
Books and Journals
Abbas, S., Nehdi, M. L. and Saleem, M. A., 2016. Ultra-high performance concrete: Mechanical performance,
durability, sustainability and implementation challenges. International Journal of Concrete Structures and
Materials. 10(3). pp.271-295.
Al-Ansari, M. and et.al., 2017. Performance of modified self-healing concrete with calcium nitrate micro
encapsulation. Construction and Building Materials. 149. pp.525-534.
Alghamri, R. and et.al., 2016. Impregnation and encapsulation of lightweight aggregates for self-healing concrete.
Construction and Building Materials. 124. pp.910-921.
Alhalabi, Z. S. and Dopudja, D. 2017. SELF-HEALING CONCRETE: DEFINITION, MECHANISM AND
APPLICATION IN DIFFERENT TYPES OF STRUCTURES. ARCHITECTURE. 5(59). pp.55-57.
De Nardi, C. and et.al., 2017. Effectiveness of crystalline admixtures and lime/cement coated granules in engineered
self-healing capacity of lime mortars. Materials and Structures. 50(4). p.191.
Dong, B. and et.al, 2015. Smart releasing behavior of a chemical self-healing microcapsule in
the stimulated concrete pore solution. Cement and Concrete Composites, 56, pp.46-50.
Feiteira, J. and et.al., 2017. Monitoring crack movement in polymer-based self-healing concrete through digital
image correlation, acoustic emission analysis and SEM in-situ loading. Materials & Design. 115. pp.238-
246.
Formia, A. and et.al., 2016. Experimental analysis of self-healing cement-based materials incorporating extruded
cementitious hollow tubes. Journal of Intelligent Material Systems and Structures. 27(19). pp.2633-2652.
Frei, R. and et. al., 2013. Self-healing and self-repairing technologies. The International Journal of Advanced
Manufacturing Technology. 69(5-8). pp.1033-1061.
Gilabert, F. A. and et.al., 2017. Determination of strength and debonding energy of a glass-concrete interface for
encapsulation-based self-healing concrete. Cement and concrete composites. 79. pp.76-93.
Goes, P. B., 2014. Design science research in top information systems journals. MIS Quarterly: Management
Information Systems. 38(1). pp.iii-viii.
Gruyaert, E. and et.al., 2016. Capsules with evolving brittleness to resist the preparation of self-healing concrete.
Materiales de Construcción. 66(323). p.092.
Han, N. X. and Xing, F., 2016. A Comprehensive Review of the Study and Development of Microcapsule Based
Self-Resilience Systems for Concrete Structures at Shenzhen University. Materials.10(1). p.2.
Hanna, K. B., 2017. A Call for Healing: Transphobia, Homophobia, and Historical Trauma in Filipina/o/x American
Activist Organizations. Hypatia. 32(3). pp.696-714.
Huang, H. and et.al., 2016. Self-healing in cementitious materials: Materials, methods and service conditions.
Materials & Design.92. pp.499-511.
Irico, S., and et.al, 2017. A solid-state NMR and X-ray powder diffraction investigation of the
binding mechanism for self-healing cementitious materials design: The assessment of
the reactivity of sodium silicate based systems. Cement and Concrete Composites, 76,
pp. 57-63.
Kalhori, H. and Bagherpour, R., 2017. Application of carbonate precipitating bacteria for improving properties and
repairing cracks of shotcrete. Construction and Building Materials.148. pp.249-260.
Kanellopoulos, A. and et.al., 2017. Polymeric microcapsules with switchable mechanical properties for self-healing
concrete: synthesis, characterisation and proof of concept. Smart Materials and Structures.26(4). p.045025.
Ketokivi, M. and Choi, T., 2014. Renaissance of case research as a scientific method. Journal of Operations
Management. 32(5). pp.232-240.
Khaliq, W. and Ehsan, M.B., 2016. Crack healing in concrete using various bio influenced self-healing techniques.
Construction and Building Materials.102. pp.349-357.
Khitab, A. and et.al., 2016. SUSTAINABLE CONSTRUCTION WITH ADVANCED BIOMATERIALS: AN
OVERVIEW. Science International. 28(3).
Lucas, S. S. and et.al., 2016. Study of quantification methods in self-healing ceramics, polymers and concrete: A
route towards standardization. Journal of Intelligent Material Systems and Structures.27(19). pp.2577-2598.
Mignon, A. and et.al., 2017. Crack Mitigation in Concrete: Superabsorbent Polymers as Key to Success?.
Materials.10(3). p.237.
40

Nishiwaki, T. and et. al., 2014. Self-healing capability of fiber-reinforced cementitious composites for recovery of
watertightness and mechanical properties. Materials. 7(3). pp.2141-2154.
Nosouhian, F. and Mostofinejad, D., 2016. Reducing Permeability of Concrete by Bacterial Mediation on Surface
Using Treatment Gel. ACI Materials Journal. 113(3).
Pamulapati, Y. and et.al., 2017. Evaluation of self-healing of asphalt concrete through induction heating and
metallic fibers. Construction and Building Materials.146. pp.66-75.
Perez, G. and et.al, 2015. Synthesis and characterization of epoxy encapsulating silica
microcapsules and amine functionalized silica nanoparticles for development of an
innovative self-healing concrete. Materials Chemistry and Physics, 165, pp.39-48.
Qian, C. and et.al., 2015. Self-healing of early age cracks in cement-based materials by mineralization of carbonic
anhydrase microorganism. Journal of front microbiology. 6.
Qureshi, T. S., Kanellopoulos, A. and Al-Tabbaa, A., 2016. Encapsulation of expansive powder minerals within a
concentric glass capsule system for self-healing concrete. Construction and Building Materials.121. pp.629-
643.
Rajesh, V. and Venugopal, M., 2017. A Study on Mechanical Properties of Bacterial Concrete Using Fly Ash and
Foundry Sand. i-Manager's Journal on Civil Engineering.7(2). p.20.
Ramadan Suleiman, A. and Nehdi, M. L., 2017. Modeling Self-Healing of Concrete Using Hybrid Genetic
Algorithm–Artificial Neural Network. Materials. 10(2). p.135.
Roig-Flores, M. and et.al., 2016. Effect of crystalline admixtures on the self-healing capability of early-age concrete
studied by means of permeability and crack closing tests. Construction and Building Materials.114. pp.447-
457.
Sangadji, S. and et.al., 2017. The Use of Alkaliphilic Bacteria-based Repair Solution for Porous Network Concrete
Healing Mechanism. Procedia Engineering.171. pp.606-613.
Šavija, B. and et. al., 2016. Simulation-Aided Design of Tubular Polymeric Capsules for Self-Healing Concrete.
Materials, 10(1), p.10.
Schlangen, E. and Sangadji, S., 2013. Addressing infrastructure durability and sustainability by
self healing mechanisms-recent advances in self healing concrete and asphalt. Procedia
engineering, 54, pp.39-57.
Seifan, M., Samani, A. K. and Berenjian, A., 2016. Bioconcrete: next generation of self-healing concrete. Applied
microbiology and biotechnology. 100(6). pp.2591-2602.
Serry, T. and Liamputtong, P., 2013. Computer-assisted qualitative data analysis (CAQDAS). Research methods in
health: Foundations for evidence-based practice. pp.380-393.
Sharma, T. K. and et.al., 2017. Alkaliphilic Bacillus species show potential application in concrete crack repair by
virtue of rapid spore production and germination then extracellular calcite formation. Journal of Applied
Microbiology.122(5). pp.1233-1244.
Talaiekhozan, A. and et.al, 2014. A review of self-healing concrete research
development. Journal of Environmental Treatment Techniques. 2(1). pp.1-11.
Van Belleghem, B. and et. al., 2016. Quantification of the Service Life Extension and
Environmental Benefit of Chloride Exposed Self-Healing Concrete. Materials. 10(1).
pp.5.
Van Tittelboom, K. and De Belie, N., 2013. Self-healing in cementitious materials—A review. Materials. 6(6).
pp.2182-2217.
Van Tittelboom, K. and et. al, 2015. The efficiency of self-healing concrete using alternative
manufacturing procedures and more realistic crack patterns. Cement and concrete
composites, 57, pp.142-152.
Van Tittelboom, K. and et. al, 2016. Comparison of different approaches for self-healing
concrete in a large-scale lab test. Construction and building materials, 107, pp.125-137.
Victor, C. L. and Emily, H., 2012. Journal of Civil Engineering Research. Journal of Civil Engineering Research.
10. pp.207-218.
Wang, J. and et.al., 2017. Bacillus sphaericus LMG 22257 is physiologically suitable for self-healing concrete.
Applied Microbiology and Biotechnology. pp.1-14.
41

Wang, J. Y. and et. al., 2014. Application of hydrogel encapsulated carbonate precipitating bacteria for approaching
a realistic self-healing in concrete. Construction and building materials. 68. pp.110-119.
Wang, X., 2013. The construction of researcher–researched relationships in school ethnography: Doing research,
participating in the field and reflecting on ethical dilemmas. International Journal of Qualitative Studies in
Education. 26(7). pp.763-779.
Wang, Y. Y. and et.al., 2016. Fabrication and characterization of self-healing microcapsules containing bituminous
re juvenator by a nano-inorganic/organic hybrid method. Construction and Building Materials. 121. pp. 471-
482.
Williams, S. L., Kirisits, M. J. and Ferron, R. D., 2017. Influence of concrete-related environmental stressors on
biomineralizing bacteria used in self-healing concrete. Construction and Building Materials. 139. pp.611-
618.
Esser-Kahn, A. P. and et.al., 2010. Programmable microcapsules from self-immolative polymers. J. Am. Chem. Soc.
132, pp10266–10268.
Gupta, S and Kua, H. W., 2016. Encapsulation technology and techniques in self healing
concrete. J. Mater. Civ. Eng.
Online
Francesco, 2014. Cracks in onshore wind turbine foundation. [Online]. Available through: <https://www.wind-
watch.org/documents/cracks-in-onshore-wind-turbine-foundations/>. [Accessed on 5th September 2017].
Sankilichitti, K., 2016. TECHKNOWLEDGE: SELF-HEALING CONCRETE OR BACTERIAL CONCRETE.
[Online]. Available through:
<http://www.adrakmail.com/ajax_main/Insight_gallery/Magazine/2016/12.December/tech.html/>.
[Accessed on 5th September 2017].
Goyal, N., 2015. Self-Healing Concrete Can Repair Its Own Cracks with Bacteria. [Online]. Available through:
<http://www.industrytap.com/self-healing-concrete-can-repair-cracks-bacteria/29051>. [Accessed on 5th
September 2017].
Yu, H. J. and et.al., 2010. The microstructure of self-healed PVA ECC under wet and dry cycles.
[Online]. Available through: <http://www.scielo.br/scielo.php?
script=sci_arttext&pid=S1516-14392010000200017>. [Accessed on 7th September 2017].
42