Self Healing Property of Concrete: Critical Appraisal and Literature Review

This critical appraisal and literature review assignment discusses the self-healing concept of concrete, including review articles and qualitative papers. It also examines two research articles for critical appraisal.

Running head: CRITICAL APPRAISAL
SELF HEALING PROPERTY OF CONCRETE
Name of the Student
Name of the University
Author note

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Abstract
Self-healingis described as the concept that enables materialswith ability to repair or heal
themselves back to their normal and original state. Concrete is determined as a brittle composite
and cementitious material which is prone to cracks and fractures if it is loaded with tensile
pressures.Concrete is a material which is termed as a sensitive material that is prone to cracks,
affecting its strength and durability. Further, due to presence of these cracks, it is become
difficult to use such structures and the maintenance costs also increases. Theself-healing property
of cementing material are of generally three groups such as intrinsic healing, capsule based
healing, and vascular healing. These three groups are classified depending on the origin of the
self-healing polymers. This critical appraisal and literature review assignment will discuss about
the self-healing concept of the concrete and in this aspect will include several review and
qualitative articles in literature review section so that each aspect of this concept could be
addressed properly. On the other hand, two research articles will be chosen for the critical
appraisal and in this aspect a specific format will be used so that complete details of the articles
and relevant critique to those research articles could be provided.

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Part 1
Introduction
Cement or concrete is the material which is known as prone to fractures or cracks with
age or under pressure of tensile pressure. Aging and presence of cracks in the concrete structure
are associated to its porous structure which makes it more prone to such degradation. As per Wu,
Johannessonand Geiker(2012), cracks can occur in any stage of life of a structure and the reason
could vary from eternal factors such as harsh environment, poor process of structure formation,
excessive tensile loading, and poor design of the structure to less durability of the used concrete
in the structure. Self-healing, on the other hand is the property of concrete which helps to change
this property of concrete and then imparts the structure with abilities which heals the
cementitious material and provides the structure with intrinsic ability so that they can heal
themselves (De Rooij et al. 2013). As the self-healing concept of the concrete is a topic of
research nowadays and from recent researches. Hence, the pathway using which self-healing
increases the bonding strength, viscosity and decreases the surface tension from the structure.
Therefore, the terms sustainability, health and strength of the concrete are important terms in this
case. Further due to these aspects of the concrete structure, the research community as well as
industrial communities are focusing on the research aspect of self-healing of concrete (Van
Tittelboom and De Belie 2013). However, the first research about self-healing property of
concrete was done in the year 1979 and in the year 2001, it was discovered that the polymers or
polymer based material which is used in the crack healing of concrete published the paper which
mentioned the structure and pathways of healing of cracks. Therefore, from the research of Van
Tittelboomand De Belie (2013) it can be easily said that with strong research aspect and hold on

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the researcher’s community, this topic is attracting industrial and private organizations. Further,
the primary approach used by such researchers to find out the primary aspects of self-healing
properties of concrete are conducting systematic review of the past research articles and
descriptive papers so that all the concepts and pathways could be easily used to demonstrate the
self-healing procedure (Huang et al. 2016).
1.2. Analysis
From the current specific knowledge and the methodologies that are available it is seen
that the cracks that are made in the concrete might happen in any stage of the service life which
might be a result of the volume instabilities related to autogenous shrinkage or drying shrinkage
(Huang, Qian and Schlangen, 2016). It is seen that the process of self-healing is a phenomenon
that is quite old and has been established to possess some of the properties which are natural
autogenous healing processes. The current researches have shown the development of the novel
techniques which involves the self-healing cracks which have been able to attract attention on a
global basis.
The different methods that have been published in several studies which includes the
various methods of self-healing in the cementitious materials. The studies have suggested that in
order to implement these in a better way. This requires the analysis of the optimal environment
required for self-healing mechanism. Based on the given aspects of self-healing related in the
cementitious materials, there were several perspectives on application of self-healing in the
engineering practice (De Belie et al. 2018).

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The papers which were published were all involved in showing that self-healing
properties were for the first time built-in inside polymeric materials. Some of the articles
published after this revealed that the publications were dealing with the self-healing properties in
thermoplastic and the systems which are crossed linked as they appeared to be. Later the papers
which were published in the 90s showed that the there was some work done on the self-healing
concrete along with the polymers (Mihashiand Nishiwaki, 2012). Later in 2001, a paper was
published which revealed that nature of the self-healing in the materials in the polymer based
materials and this research was able to attract a lot of attention (Van Tittelboom and De Belie,
2013). The papers were connected in the way that showed that the different approaches were able
to explain the process of self-healing. The published articles were also able to show the several
advantages and disadvantages related to the different types of healing agents along with the
techniques of encapsulation which were discussed. This was then followed with the mechanisms
which were responsible for triggering the mechanisms of self-healing.

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Figure 1. Puplished papers related to self-healing materials
Some of the limitations that were met through the methodologies of the process of self-
healing materials suggested that it was required to obtain the properties of self-healing in the
cementitious materials which are different from the ones which are already mentioned. It was
quite difficult to select the approach that is most efficient in terms of the process since each of
the research groups have implemented their own test methods in order to evaluate the efficiency
of healing (Gardner et al. 2017).
There are certain methodologies which are more promising than the ones being
discussed. These methods will be able to conduct the autogenous healing which will be able to
be confined to the small cracks and there will be more reliability of the autogenous healing since
there is a dependence of the composition of the matrix, where the feasible reaction mechanisms
are determined especially at the moment of the crack formation. In regards to the capsule- and
tubular based self-healing, the agents of healing are able to react while they are in contact with
the air and moisture (Davies and Jefferson 2017). There is a possibility of using the tubular and
the spherical capsules which are dependent on the efficient respond which are mentioned
properties. However this too has certain limitations since there is a probability of the crack
hitting the capsule which in turn releases the efficiency thereby the healable crack volume
becomes relatively high. This approach of tubular encapsulation is most of the time only
applicable for the concrete elements which are precast as a manual introduction of the tubular
capsules which are required.

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1.3 Research opportunities
With respect to the research opportunities, it is clear that this research topic of self-
healing concrete is truly interdisciplinary in nature as there is an involvement of various aspects
like that of chemistry, microbiology, material science along with civil engineering. Therefore in
order to choose the most efficient method of the process it is necessary to be able to apply the
approach of self-healing along with the cross-disciplinary cooperation along with vivid
communications among the involved researchers having a range of expertise which will be of
utmost importance (Gardner et al. 2018). Although it is seen that in regards to the in-situ
application, the process of self-healing which will mainly be dependent on the required cost.
There is a requirement of keeping the cost of the mechanism quite low as well as preferential in
comparison to the indirect and the direct repair cost.
Figure 2: Autogenous self-healing due to precipitation of calcium carbonate in the
presence of water and dissolved carbon dioxide.

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The possible engineering benefits are based on the mineral admixtures along with self-
healing which is based on the bacteria along with that of the adhesive agents which have also
been reviewed. The existing literature has shown that most of the mechanisms related to self-
healing are effective in nature however some are applicable in the particular conditions (Blaiszik
et al. 2010). In the context of the previously conducted studies, there are conditions which are
favourable for each of the mechanism of self-healing as has been analysed. It is seen that the
presence of water in the cracks leads to the development of a negative effect. In case of the self-
healing being based in the bacteria, the presence of the CO3 2− ions is considered as a primary
condition however this is not the same for the other mechanisms. In terms of real engineering
applications, it is important that the techniques of self-healing be chosen in accordance to the
conditions of service of the concrete structures. It has also been seen that there are additional
costs for the application of the self-healing in terms of engineering purposes (De Belie et al.
2018). This is however difficult to quantify since there are certain prime techniques for the
realization of self-healing like the process of encapsulation along with the coating of mineral
admixtures, which is still being developed. The studies that are being conducted on self-healing
in an in-situ setting are not that satisfactory which has led to the repeatability of self-healing of
the crack which are under the repeated loads. There is no such determination available between
the self-healing of cracks and extension of service life (Sh, and Dopudja2017).

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Figure 3: Schematic description of the self-healing system

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Part 2
Paper 1 Davies, R., Teall, O., Pilegis, M., Kanellopoulos, A., Sharma, T., Jefferson, A.,
Gardner, D., Al-Tabbaa, A., Paine, K. and Lark, R., 2018. Large Scale
Application of Self-Healing Concrete: Design, Construction, and
Testing. Frontiers in Materials.
Why do you think that the paper is of high quality and academic standards
Journal quality: the journal selected for this research article is frontiers in materials which
is an open access high visibility journal that publishes research papers which are rigorously
peer reviewed. The impact factor of this journal is 2.008. The impact factor is known as the
average of citations of that article researches use in their research within a year. Hence, it
could be said that this journal is moderately preferable for the research community and the
quality of the journal is good and contains high quality papers on material science and
engineering.
Recognition of authors: all the authors are working in universities like Cardiff University,
University of Bath, and University of Hertfordshire and so on which are dedicated for
research about concrete and they worked in the structural engineering department.
Rigour of the paper: as rigour of the paper is discussion about the strengths of the research
process and this article is a review of previous articles, the review and its strength will be
discussed. This review mainly concentrated on the first site trial of the UK’s self healing
concrete. This trail used four self healing techniques and then determined the effectiveness
of all the processes.
Writing quality: the writing of the research article was lucid and all the paragraphs were
connected in such a way which would help the reader to understand the concepts properly.
Impact of the result: the study affects the concepts of the self-healing as it mentions the
pros and cons of each healing process and compared the in situ and external application of
the three processes of self-healing in the onsite trails which increases its effectiveness and
application ability in real time.
Why is this paper relevant to your literature review?
The paper is relevant in various aspects as it helped to understand the four aspects of self
healing and then discussed the effectiveness of each of it in a similar environment. It
provided a detailed idea of self healing techniques on a concrete and conducted an onsite
trail of these processes so that it could be determined. Further, there were linkages between
this research article and other articles included in this literature review as all of them
discussed about the same concept in different aspects and provided a detailed process of
healing, future aspect of this concept in making the structures less prone to cracks and
fractures. Besides this it also included factors which can be incorporated in full scale
structures so that self healing technique of those structures could be understood.
Summary of selected paper
Aim The aim of this paper was to discuss the site trial concept and

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design, the trial panel contents and construction details, the loading
configuration and monitoring undertaken and a summary and
discussion on the key findings of the trial.
Hypotheses and
methodology
As the article was a descriptive article discussing about a concept or
design of self healing concepts on concrete and presented all the
concepts in equal environment, it does not have any hypothesis and as
methodology they conducted analysis of the tests and trails done in this
onsite trail so that the the self-healing concept of concrete could be
presented.
Main findings Researchers were able to determine the self healing concrete and
visualize in large scale, effect of self healing in crack width and then the
structural behaviour of concrete and hence, these were the findings
which elevated the understanding of researchers about self healing and
concrete health.
Novelty Application of all four type of self healing approaches and concepts
were the novelty of this research process further the researchers were
also able to understand the scaling up process of healing technique and
other aspects which increases the novelty of the process.
Limitations
and
opportunities
for further
research
Due to descriptive approach of this review article, it did not provided
any limitation of the study. However, the future aspect of this study
was bright as it provided detailed analysis of processes in an future
research opportunity for this healing process of concrete.
Paper 2 Huang, H., Ye, G., Qian, C. and Schlangen, E., 2016. Self-healing in
cementitious materials: Materials, methods and service conditions. Materials &
Design, 92, pp.499-511.
Why do you think that the paper is of high quality and academic standards
Journal quality: the journal quality of this journal Elsevier is excellent as the impact factor
or the average number of citation used by researchers is 8.57 and hence, this research
journal is of best quality.
Recognition of authors: the authors were recognised as they all worked in reputed
universities and were destined to determine the self-healing process of cementitious
material
Rigour of the paper: the article was able to provide novelty in its finding and presented a
comparison between different methods. This article was the first research article that
included self-healing property related agents and their role in the process.
Writing quality: the paper was lucid and the flow pf language was good and all the
paragraphs were connected which made the information placed in sequence.
Impact of the result: this paper and its result impacted these results properly and influenced
the research topic and other research processes.
Why is this paper relevant to your literature review?
This paper was relevant to literature review as it helped to identify the methods and its

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specifications of self-healing in concrete. in addition it also presented some research
evidences which has been implement and also some sections which can be used as
promising future prospect.
Summary of selected paper
Aim The aim of the paper was to explain the mechanisms of self-healing in
cementitious materials, i.e. autogenous self-healing, self-healing based
on mineral admixtures, self-healing based on bacteria and self-healing
based on adhesive agents and review them.
Hypotheses and
methodology
As the paper was descriptive, it did not had any hypothesis and
methodology for discussion of the study
Main findings The article was able to find a novel idea and provided the required
environmental conditions for each self-healing mechanism as well as
these were analyzed. Additional costs for realizing self-healing in
concrete structures are also discussed.
Novelty This paper was able to provide a complete review on self-healing
process
Limitations
and
opportunities
for further
research
The limitations were:
As the capsules are randomly dispersed in the matrix, only a small part
of them can be hit and ruptured by cracks.
Despite the fact that a crack initiating in the bulk matrix hits a capsule,
it is still possible that the crack deflects along the interface between the
capsule shell and the bulk matrix.
Further these aspects widened the future research aspect about this
topic.

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References
Blaiszik, B.J., Kramer, S.L., Olugebefola, S.C., Moore, J.S., Sottos, N.R. and White, S.R., 2010.
Self-healing polymers and composites. Annual review of materials research, 40, pp.179-211.
Davies, R. and Jefferson, A., 2017. Micromechanical modelling of self-healing cementitious
materials. International Journal of Solids and Structures, 113, pp.180-191.
De Belie, N., Gruyaert, E., Al‐Tabbaa, A., Antonaci, P., Baera, C., Bajare, D., Darquennes, A.,
Davies, R., Ferrara, L., Jefferson, T. and Litina, C., 2018. A Review of Self‐Healing Concrete for
Damage Management of Structures. Advanced Materials Interfaces, p.1800074.
De Rooij, M., Van Tittelboom, K., De Belie, N. and Schlangen, E. eds., 2013. Self-healing
phenomena in cement-Based materials: state-of-the-art report of RILEM technical committee
221-SHC: self-Healing phenomena in cement-Based materials(Vol. 11). Springer Science &
Business Media.
Gardner, D., Herbert, D., Jayaprakash, M., Jefferson, A. and Paul, A., 2017. Capillary Flow
Characteristics of an Autogenic and Autonomic Healing Agent for Self-Healing
Concrete. Journal of Materials in Civil Engineering, 29(11), p.04017228.
Gardner, D., Lark, R., Jefferson, T. and Davies, R., 2018. A survey on problems encountered in
current concrete construction and the potential benefits of self-healing cementitious
materials. Case studies in construction materials, 8, pp.238-247.
Huang, H., Ye, G., Qian, C. and Schlangen, E., 2016. Self-healing in cementitious materials:
Materials, methods and service conditions. Materials & Design, 92, pp.499-511.

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Mihashi, H. and Nishiwaki, T., 2012. Development of engineered self-healing and self-repairing
concrete-state-of-the-art report. Journal of Advanced Concrete Technology, 10(5), pp.170-184.
Sh, A.Z. and Dopudja, D., 2017. SELF-HEALING CONCRETE: DEFINITION, MECHANISM
AND APPLICATION IN DIFFERENT TYPES OF STRUCTURES. Международныйнаучно-
исследовательскийжурнал, (05 (59) Часть 1), pp.55-57.
Van Tittelboom, K. and De Belie, N., 2013. Self-healing in cementitious materials—A
review. Materials, 6(6), pp.2182-2217.
Wu, M., Johannesson, B. and Geiker, M., 2012. A review: Self-healing in cementitious materials
and engineered cementitious composite as a self-healing material. Construction and Building
Materials, 28(1), pp.571-583.