Revista Facultad de Ingeniería, Universidad de Antioquia, No.110, pp. 99-109, Jan-Mar 2024
Flaw recognition in reinforced concrete
bridges using infrared thermography: A case
study
Reconocimiento de defectos en puentes de hormigón armado utilizando termografía
infrarroja: estudio de caso
Joaquin Humberto Aquino-Rocha 1*, Yêda Vieira-Póvoas 2, Pedro Igor. Bezerra-Batista 2
1Programa de Engenharia Civil - PEC/COPPE/UFR, Universidade Federal de Rio de Janeiro. Cidade Universitária, Ilha do
Fundão. CEP 21941-972. Rio de Janeiro, Brazil.
2Programa de Pós-Graduação em Engenharia Civil - PEC/POLI/UPE, Universidade de Pernambuco. Rua Benfica, 455 –
Madalena. CEP 50720-001. Recife, Brazil.
CITE THIS ARTICLE AS:
J. H. Aquino-Rocha, Y.
Vieira-Póvoas and P. I.
Bezerra-Batista. ”Flaw
recognition in reinforced
concrete bridges using
infrared thermography: A case
study”, Revista Facultad de
Ingeniería Universidad de
Antioquia, no. 110, pp. 99-109,
Jan-Mar 2024. [Online].
Available: https:
//www.doi.org/10.17533/
udea.redin.20230521
ARTICLE INFO:
Received: January 20, 2022
Accepted: May 15, 2023
Available online: May 15, 2023
KEYWORDS:
Non-destructive tests; bridge
Inspection; recognition;
thermal gradients
Ensayo no destructivo;
inspección de puentes;
reconocimiento; gradientes
térmicos
ABSTRACT: Infrared thermography is a non-destructive test that is increasingly used in the
inspection of existing buildings, bridges, and civil works. However, its practice is limited
due to the influence of environmental conditions on the results of the test. The present
study aims to evaluate the methodology of the test through the inspection of existing
reinforced concrete bridges in Recife, Brazil. This city presents different environmental
conditions from those reported in the literature, a high ambient temperature and relative
humidity. The study comprises the inspection of five bridges in two days, analyzing their
superstructure and infrastructure separately. The results show that flaw recognition is
possible through the temperature gradient between imperfect and intact regions. Thus,
variation in temperature greater than 0.3 °C allows awareness of the problem. The
results behavior is different based on the bridge section inspected. The defects in the
bridge superstructure are presented as positive thermal gradients. On the other hand,
bridge infrastructure’s deficiencies are shown as negative thermal gradients. Although
the technique presents several advantages for the inspection, the results must be
analyzed in detail to avoid false detections, which may compromise the correct diagnosis
of the bridge structures.
RESUMEN: La termografía infrarroja es una prueba no destructiva que se utiliza cada vez
más en la inspección de edificios, puentes y obras civiles existentes. Sin embargo,
su práctica es limitada, debido a la influencia de las condiciones ambientales en los
resultados de la prueba. El presente estudio tiene como objetivo evaluar la metodología
de la termografía infrarroja a través de la inspección de puentes existentes de hormigón
armado en Recife, Brasil. Esta ciudad presenta condiciones ambientales diferentes a las
reportadas en la literatura, una elevada temperatura ambiental y humedad relativa. El
estudio comprende la inspección de cinco puentes en dos días, analizando por separado
su superestructura e infraestructura. Los resultados muestran que el reconocimiento
de defectos es posible a través del gradiente de temperatura entre regiones imperfectas
y regiones intactas. Por lo tanto, una variación de temperatura superior a 0.3 °C
permite conocer el problema. El comportamiento de los resultados es diferente según
la sección de puente inspeccionada. Los defectos en la superestructura del puente
se presentan como gradientes térmicos positivos. Por otro lado, las deficiencias de la
infraestructura del puente se mostraron como gradientes térmicos negativos. Aunque la
técnica presenta varias ventajas para la inspección, los resultados deben analizarse en
detalle para evitar detecciones falsas, lo que puede comprometer el diagnóstico correcto
de las estructuras del puente.
1. Introduction
Concrete bridge deterioration is a common problem in both
developing and developed countries; therefore, preventive
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* Corresponding author: Joaquin Humberto Aquino-Rocha
E-mail: joaquinaquinorocha@gmail.com
ISSN 0120-6230
e-ISSN 2422-2844
DOI: 10.17533/udea.redin.20230521 99

J. H Aquino-Rocha et al., Revista Facultad de Ingeniería, Universidad de Antioquia, No. 110, pp. 99-109, 2024
actions are necessary to guarantee the useful life of these
structures. In this sense, inspection and maintenance
activities are important to ensure the safety and correct
functionality of a structure. However, bridge structures’
inspection and maintenance tasks have become a slow
process with high fare frequencies [1–3]. As stated by
Brazilian code NBR 9452 [4], bridge inspections can be
conducted within a period of a year to eight years at most,
for routine or special inspections, respectively.
The most common bridge inspection technique is visual
inspection [5, 6], but the information obtained is qualitative
and subjective. This makes it impossible to provide a
trustworthy diagnosis of the state of the structure [7].
Destructive testing methods are also used to investigate
the structure’s current conditions. Core sample extraction
is vastly used to perform mechanical tests (i.e., tensile
testing, bending testing, compressive testing, hardness
testing, impact testing), but these methods cause the
interruption of the structure operability, in some cases
endangering the mechanical properties of the structure
[8].
Due to the high cost of reparation, rehabilitation, and
replacement of reinforced concrete bridge elements, it is
necessary to use efficient methods for flaw recognition
and deterioration degree quantification. To find out the
most efficient technique with minimal impact on traffic
service [9]. In this context, several non-destructive
methods have been developed for an effective bridge
inspection: Impact-Eco (IE), Ultrasonic Testing (UT),
Electrical Resistivity (ER), Ground Penetrating Radar
(GPR), Infrared Thermography (IRT), among others [5–11].
Infrared thermography is a non-destructive test used
to detect unnoticeable anomalies in concrete structures,
such as delaminations and voids [12–14]. This technique
helps reduce inspection time, enabling access to areas
that cannot be inspected with traditional methods. Its use
in bridge inspection is recommended since it does not
require direct contact, and is a fast procedure. In addition,
it does not require traffic interruption; it is easy to collect
data, and presents immediate results [1, 5, 9, 15–17]
There are several academic research regarding defect and
delamination detection in reinforced concrete bridges with
infrared thermography, both experimentally and in situ
[2, 7, 14, 17–19]. Many authors have established different
relationships between the defect’s detectability, size and
depth. Because the more superficial and larger the flaw,
the more efficient it is to detect with the thermographic
camera [20–22].
Some authors compared the detection of defects
experimentally and through numerical simulations
[10, 23]. The findings point out adequate inspection periods
and limitations of the technique in terms of atmospheric
conditions and obstacles that may interfere with the
results. In this sense, the detection efficiency depends on
specific periods and favorable environmental conditions
[2]. Alike, direct solar flare loading, temperature variation,
and wind conditions affect acquiring adequate results
[12]. Other authors mentioned that detection is successful
when there is a considerable temperature difference
between the fault’s surface and the undamaged concrete.
To illustrate, some studies advised a difference of 0.8
°C [17] and 0.3 °C [24]. Moreover, detecting internal
imperfections is more viable during nighttime due to the
cooling effect [25]. However, an accurate characterization
of internal defects should complement this examination
with additional non-destructive tests [7, 16, 25, 26].
Although ASTM D4788-03 [27] provides practical
guidelines for bridge inspection employing infrared
thermography, this standard is limited only to assessing
elements on the bridge superstructure subjected to direct
solar exposure. Other investigations were able to assess
the defects in concrete elements (e.g., beams and piles)
that were not exposed to direct solar radiation up to 50
[28] and 76 mm [29] deep. Surprisingly, defect detection
can be performed on moving vehicles as well [30, 31]
and with the aid of Unmanned Aerial Vehicles (UAV) [32].
For these latter scenarios, thermographic cameras with
better features are required.
Despite improvements in the area, further research
is still required to consolidate infrared thermography as
an alternative method for inspecting bridges. The latter
is deduced from the different conclusions reported when
the technique is applied in different places and conditions
[2, 9, 24, 30]. More experimental studies with controlled
concrete specimens are presented in the literature, where
the material’s mechanical features and the exact location
of defects are known. For in-situ analyses, the results are
specific to the site conditions. Therefore, its practice can
be distorted when applied in other regions or places like
Brazil, due to different environmental conditions. In this
sense, the present study aims to evaluate the applicability
of the infrared thermography testing in the inspection
of reinforced concrete bridges in the city of Recife,
considering this region displays different environmental
conditions. The latter is based on academic research
conducted in the literature. Thus, an additional reference
to the on-field applicability of infrared thermography
is provided, consolidating its use for the inspection of
concrete structures.
2. Methodology
To investigate the applicability of infrared thermography
in the detection of defects in bridges, inspections
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J. H Aquino-Rocha et al., Revista Facultad de Ingeniería, Universidad de Antioquia, No. 110, pp. 99-109, 2024
Figure 1 Block diagram of the system components. Adapted from [33]
were carried out on reinforced concrete bridges in the
downtown area of Recife. A total of five bridges were
inspected: Duarte Coelho, Princesa Isabel, Buarque de
Macedo, Maurício de Nassau, and Giratória. Figure 1
shows the location of the bridges in the present study.
The inspections were conducted investing two workdays.
On the first day, the infrastructure of the bridges was
inspected from 2 pm to 4 pm. This included a temperature
of 30.5 °C and a relative humidity of 71%. On the second
day, the superstructure of the bridges was inspected from
10:00 am to 12:00 pm, at an ambient temperature of 31.2
° C and a relative humidity of 66%. These values were
determined using a digital thermo-hygrometer.
Although several authors recommend different
times to detect abnormalities in reinforced concrete
[2, 9, 12, 16, 25, 29], the inspection times were chosen
based on previous research [34]. Additionally, Standard
D4788-03 [27] was used as a guide for bridge inspection,
including infrared thermography.
The present study does not intend to carry out a
detailed inspection of each bridge. The main goal is
a general inspection to assess the technique’s ability to
detect defects. In addition, it is necessary to present the
technique as a complement and aid in visual inspection,
providing significant information data for a more complete
diagnosis of these structures.
The form of application of infrared thermography was
passive, using the sun’s presence to heat the elements
in the superstructure and the ambient temperature
for the areas of the infrastructure. The thermograms
were captured with a FLIR E-60 camera, which allows
inspection of specific sectors. In addition, it provides
results in real time. The camera simultaneously captures
digital photographs and thermograms. The infrared
camera was calibrated by the manufacturer two months
before testing, by following recommendations in the user’s
manual [35]. Table 1 shows the main characteristics of the
thermographic camera used.
The distance from the camera to the inspected bridge
elements was between two and four meters. In each
thermogram taken, the camera’s focus was adjusted
to obtain a good image resolution. The emissivity was
calculated using the black tape method, where a known
emissivity tape is used. A piece of tape was fixed to the
concrete surface; thus, the object’s emissivity value is
determined through iterations until the temperature of
the concrete matches the temperature of the tape. This
last value corresponds to the emissivity of the concrete.
The emissivity was determined in each bridge, both in the
superstructure and infrastructure. Acquired values vary
between 0.94 and 0.95, according to the range suggested
for the concrete by NBR 15220 standard [36].
For the reflected temperature, the reflection method was
used. This procedure is described in the camera manual
[35], which consists of measuring the temperature of a
bent and crushed aluminum part and taking an emissivity
value equal to one. This parameter was calculated for
each thermogram obtained. Once thermograms were
obtained, data were analyzed using FLIR Tools software
to obtain the temperature for each point. In addition to
thermographic qualitative information, thermal contrast,
T , was used as defined by Equation 1, to detect failure
detection to be analyzed afterwards.
∆T = Ta − Tb (1)
Where, Ta is surface temperature for apparent failure, and
Tb is intact concrete temperature.
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Table 1 Characteristics of the FLIR E-60 thermal
camera
Model FLIR E-60
IR Resolution (Array size) 320 × 240 pixels
Thermal sensitivity < 0.05◦C
Temperature range -20 to 650◦C
Accuracy ±2% rdg. or 2◦C
Visual camera 3.1 MP
Source:[35]
3. Analysis and discussion of results
The analysis and discussion of the results are presented
according to the inspected sector of the bridges:
superstructure and infrastructure.
3.1 Superstructure
Figure 2a shows a portion of the superstructure close to
the main slab of the Duarte Coelho bridge. This section
was exposed to the sun in a northern direction (N) where
detached areas and exposed steel are observed. However,
Figure 2b shows three hot areas not visible in the digital
image. This shows temperature differences of 0.9 ° C
(Sp2-Sp1), 1.2 °C (Sp3-Sp1) and 1.4 °C (Sp4-Sp1). Also,
it indicates the presence of defects internal in concrete,
such as delamination and voids. These problems are
presented as sectors of higher temperature in relation to
intact concrete when exposed to the sun [12, 30]. The
thermogram is included within the red frame of the digital
image. The yellow colors represent high temperatures,
while the colors in purple tones lower temperatures.
Figure 3b presents the thermogram of the beams of the
Princesa Isabel bridge in a northern direction (N), where
a small hot area (Area 1) is observed. This area may
represent a surface problem in the concrete with a thermal
difference of 0.7 °C (Sp2 -Sp1). Larger hot areas (Area 2)
with temperature differences of 0.9 °C (Sp3-Sp1) can also
be observed in the same thermogram; however, they are
not considered as delaminations or defects. As can be
seen in Figure 3a, these regions depict the wearing and
peeling of the paint on the concrete. The latter allowed the
development of irregularities in the surface temperature in
this stretch.
Figure 4a presents the parapet of the Maurício de Nassau
bridge exposed to direct sunlight in a northern direction
(N). Here, no visible defects are observed, due to some
repairs made and the new coat of paint. However, Figure
4b shows several delaminated areas. These areas are
depicted as hot areas because of the sun exposure that
warms the areas above the delaminations faster than the
areas without defects [10, 12]. The measured temperature
differences are greater than 1 °C at the points analyzed:
1.6 °C (Sp2-Sp1), 1.5 °C (Sp3-Sp1) and 1.3 °C (Sp4-Sp1).
Figure 5a presents the digital image of the surface exposed
to the sun from the superstructure of the Giratória bridge.
The transverse section of the bridge is composed of a
prestressed concrete cell box in a northeast direction (NE),
in which no apparent damage was observed. However, the
thermogram illustrated in Figure 5b shows two thermal
gradients on the concrete surface, indicating defects
or internal delaminations. Although the temperature
differences are insignificant, 0.3 ° C (Sp2-Sp1) and 0.4 ° C
(Sp3-Sp1).
The development of detachments, voids, delaminations,
and cracks in bridge elements due to corrosion of the steel
or failures in the construction process can be detected
with infrared thermography, only when these surfaces
are exposed to solar radiation. The latter heats the
concrete elements, providing a high thermal gradient
between the intact areas and the defects, which allows
detection on the surface [12]. In the superstructure of
the inspected bridges, all defects are detected as positive
thermal gradients. This behavior can be described by the
heating of the concrete through the incidental radiation
from the sun and the heat convection with the environment,
being the first source, the most important in the heat
transfer process. During the day, solar radiation reaches
the concrete surface, where it is partially absorbed and
partially reflected, as can be seen in Figure 6. The
absorbed radiation is transferred through the concrete.
This transfer is reduced until reaching the delamination,
which has thermal conductivity different from the concrete
[30, 31]. The more superficial the delamination or defect
is, the faster the concrete above heats up as it is a small
area to heat compared to other deeper defects. This
represents a larger area to be heated by the same amount
of absorbed radiation. In this case, the more superficial
defects acquire a higher temperature, the higher radiation
emitted. This phenomenon was captured by the camera
as positive thermal gradients on the surface, as can be
seen in Figure 7. Deeper defects may show some radiation
difference, but it is minimal, and it is not captured and
visualized in the thermograms.
Standard D4788-03 [27] indicates at least three hours of
sun exposure for the detection of defects in reinforced
concrete bridges. The tests were carried out from
10:00 am. This provided more than 4 hours of sun
exposure. Thus, satisfactory results were obtained in the
superstructure.
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(a) (b)
Figure 2 Superstructure of the Duarte Coelho bridge: a) Digital image and b) Thermogram. Source: The Authors
(a) (b)
Figure 3 Superstructure of Princesa Isabel bridge: a) Digital image and b) Thermogram. Source: The Authors
(a) (b)
Figure 4 Concrete parapet of the Maurício de Nassau bridge: a) Digital image and b) Thermogram. Source: The Authors
3.2 Infrastructure
Figure 8a and Figure 9a show the slab and beams of
the Duarte Coelho bridge infrastructure where signs
of previous repairments can be seen. Figure 8a shows
a damaged area with exposed steel; this can also be
detected in Figure 8b. In addition, other invisible areas
in the digital images are depicted, indicating that the
detached and delaminated areas have been covered. The
latter appear as colder sectors in the thermograms; this
situation is due to the gradient of temperature existing
inside the slab. However, the defects interfere with
the heating of the areas below themselves, presenting
as negative gradients or cold spots. The hotter areas
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J. H Aquino-Rocha et al., Revista Facultad de Ingeniería, Universidad de Antioquia, No. 110, pp. 99-109, 2024
(a) (b)
Figure 5 Giratória bridge: a) Digital image and b) Thermogram. Source: The Authors
Figure 6 Radiation incident on the superstructure. Source: The Authors.
Figure 7 Radiation emitted by the superstructure surface. Source: The Authors.
indicate intact areas without defects. Because they allow
heat transfer without interference. The temperature
variations are -2.0 °C (Sp2-Sp1), -0.6 °C (Sp3-Sp1), and
-2.6 °C (Sp4-Sp1). In the thermogram of Figure 9b, the
differences are -1.5 °C (Sp2-Sp1) and -1.6 °C (Sp3-Sp1).
Figure 10a presents the beams of the Princesa Isabel
bridge in the infrastructure area. Two damaged areas
were observed: Area 1 displays an evident deterioration,
but in the thermogram of Figure 10b, there are no
significant variations in temperature, -0.3 °C (Sp2-Sp1).
This indicates that this area is not delaminated or at
risk of detachment. Nonetheless, this may be a sign
of localized corrosion; thus, the concrete has already
detached. Area 2 also shows deterioration and detached
parts with exposed steel. The thermal image shows a
larger cold area, -1.4 °C (Sp4-Sp3), indicating generalized
corrosion and regions at risk of being detached. As the
areas are in the infrastructure, there is no direct solar
radiation; thus, there is a cold environment in relation
to the superstructure. The delaminated and detached
regions balance more rapidly with the environment
than other areas, which need more time to achieve this
equilibrium.
Figure 11a presents the lower area of the sidewalk with
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J. H Aquino-Rocha et al., Revista Facultad de Ingeniería, Universidad de Antioquia, No. 110, pp. 99-109, 2024
(a) (b)
Figure 8 Duarte Coelho bridge infrastructure 1: a) Digital image and b) Thermogram. Source: The Authors
(a) (b)
Figure 9 Duarte Coelho bridge infrastructure 2: a) Digital image and b) Thermogram. Source: The Authors
(a) (b)
Figure 10 Infrastructure of Princesa Isabel bridge: a) Digital image and b) Thermogram. Source: The Authors
the support pier of the Buarque de Macedo bridge. This
sector has no sun exposure because it is in the south (S)
direction. It is observed in Figure 11b that the cracks and
the delaminated areas are presented as cold in relation
to the intact concrete that has a higher temperature.
The latter can be verified in the temperature variation
between different points of the structural element, -1.5
°C (Sp2-Sp1) and -2.6 °C (Sp3-Sp1). In addition, the
infiltration located in the beam wall is cold due to the
presence of water with a temperature difference of -2.5 °C
(Sp4-Sp1).
Figure 12a displays a deteriorated area with corroded and
exposed steel from the Buarque de Macedo bridge. Figure
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(a) (b)
Figure 11 Lower sidewalk area of the Buarque de Macedo bridge: a) Digital image and b) Thermogram. Source: The Authors
12b shows that this area is completely cold compared
to other areas, -2.8 °C (Sp2-Sp1), suggesting a large
area delaminated by corrosion due to the wetting and
drying process that this sector underwent. Moreover, a
possible infiltration in the bridge is considered, among
other factors, as the cause of this behavior.
Figure 13a presents the lower section of the footpath of
the Maurício de Nassau bridge. This section is in the south
direction (S), which does not receive direct sunlight during
the day. In Figure 13b, the detachments and defects are
also shown as cooler areas. The temperature differences
of the analyzed points are: -0.4 °C (Sp2-Sp1), -0.3 °C
(Sp3-Sp1), -0.6 °C (Sp4-Sp1), -0.3 °C (Sp5-Sp1) and -0.7
°C (Sp6-Sp1).
From the analyzed cases, it can be noted that the
infrastructure presents an opposite behavior compared to
the superstructure, which is attributed to the non-direct
contact of sunlight to develop gradients of temperature.
However, the gradient occurs during the equilibrium of
the concrete temperature and the ambient temperature
through the convection mechanism close to the surface.
In this case, the areas above the most superficial internal
defects balance rapidly with the environment. Because
they exhibit smaller areas in comparison to the deeper
delaminations, they develop negative gradients, appearing
as colder areas [12]. Furthermore, it is important to
mention that gradients are also developed indirectly by
the radiation of the sun, since the elements are heated at
the top, transferring heat to the bottom, as can be seen
in Figure6. Nevertheless, defects and detachments in the
concrete interrupt this transfer and lead to a retention of
heat in upper areas, presenting themselves as regions with
a lower temperature in relation to the intact concrete that
is uniformly heated. These areas of lower temperature
emit less infrared radiation, which allows the formation
of thermal gradients, as can be seen in Figure 14. The
warmest areas represent sectors of the intact concrete
where heat transfer is normal.
Detection may be limited when infrared thermography is
applied to parts not exposed to direct sunlight, such as
infrastructure. However, delaminations and defects can
be detected efficiently when the temperature variations
during the day are large enough to generate noticeable
gradients due to the great mass and the low conductivity
of the concrete [12, 28, 29].
Infrared thermography allows the detection of defects in
reinforced concrete bridges during the inspection. The
results vary according to the bridge sector analyzed.
Also, they are influenced by factors such as ambient
temperature and sun exposure. The temperature variation
between the intact and defective areas is fundamental
for detection. In the present study, differences greater
than 0.3 °C allowed identification. However, the standard
code D4788-03 [27] establishes at least 0.5 °C of thermal
differential and other authors consider values above 0.8
°C [24]. The results presented indicate that the detection
can be performed with lower values; gradients of 0.2 and
0.3 °C are enough to detect defects in the concrete [2, 17].
Although cameras with higher resolution are better
for inspection [30], it was found that the FLIR E-60
camera with lower resolution and thermal sensitivity
features has the same potential to detect delaminations
and defects in reinforced concrete structures [2, 16, 24, 29].
The technique provides more information on the state
of bridge structures than a visual inspection, but it is
necessary to corroborate the results obtained. Thus, other
non-destructive techniques can be used as other authors
have done in their research, such as the use of GPR or IE
[5, 7, 25, 26], to name a few. Infrared thermography results
are consistent with previous research [37], where studied
bridges present diverse pathological manifestations,
such as: cracks, infiltrations, corrosion, and steel
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(a) (b)
Figure 12 Buarque de Macedo bridge infrastructure: a) Digital image and b) Thermogram. Source: The Authors
(a) (b)
Figure 13 Lower area of the Maurício de Nassau Bridge sidewalk: a) Digital image and b) Thermogram. Source: The Authors
Figure 14 Radiation emitted by the infrastructure surface. Source: The Authors.
reinforcement exposure. The authors point out that these
problems are mainly caused by chloride ion penetration
(marine environment). Although bridge concrete has a
satisfactory sclerometric index, it is compromised by an
advanced corrosion process.
4. Conclusions
In the present work, field research was conducted to
analyze the detection of internal defects in reinforced
concrete bridges through infrared thermography in the
city of Recife, Brazil. Detection is possible with this
technique but is limited to certain inspection times of the
day. Consequently, previous tests must be carried out in
the structure as a complement to the inspection procedure.
The analysis in the detection of defects is different
according to the sector inspected. In the superstructure,
the problems are detected as positive thermal gradients;
however, in the infrastructure, as negative thermal
gradients. Direct solar radiation is the main source of
temperature gradient developments in the superstructure
and indirectly in the infrastructure as well. However,
the ambient temperature also favors the development of
temperature differences by the convection mechanism;
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the latter is true, especially for the infrastructure.
The results are qualitative, but most of them can be
used to lay down and define the affected areas. An
analysis of the values of the thermal gradients can
point out the defects that are more superficial than
others are; considering that the greater the variation,
the more superficial the problem is. The environmental
conditions in Recife City are suitable for the use of
the technique in bridge inspections, since temperature
differences were detected and allowed the detection of
problems in the concrete, both in the superstructure and
infrastructure. It is important to highlight that this study
was limited to a specific case study, including specific
environmental conditions, high relative humidity, and
ambient temperature, besides only considering passive
implementation. Other results may be present when this
technique is applied in other conditions or even including
active infrared thermography.
In this study, failure areas were detected and located;
however, it was not possible to determine the damage
nature or extent. The present study was limited to the
analysis of delaminations and cracks, being the only
defects visualized by the thermal camera. Other failures
might require another detection approach. Therefore,
infrared thermography combined with non-destructive
testing for better flaw characterization may be employed
for further research.
In this sense, considering other variables and conditions
for future work is required. Tests in different seasons
of the year may be considered. Since relative humidity
and ambient temperature vary yearly on average, they
may affect results, even for inspections at night hours
before structural thermal balance with the environment to
determine viable planning for flaw detection.
Although infrared thermography has made progress
in recent years for the inspection of civil structures,
especially bridges, there are few standards that govern
the execution of the technique and few parameters
recommended for the analysis of results. In this sense,
more conclusive and comparative research is needed
to determine the reliability of its application for these
purposes.
5. Declaration of competing interest
We declare that we have no significant competing interests
including financial or non-financial, professional, or
personal interests interfering with the full and objective
presentation of the work described in this manuscript.
6. Funding
This work was supported by Coordenação de
aperfeiçoamento de pessoal de nivel superior (CAPES).
7. Author contributions
Joaquin Humberto Aquino Rocha: Conceptualization,
Methodology, Formal analysis, Investigation, and Writing
- Original Draft.
Yêda Vieira Póvoas: Visualization, Methodology, and
Writing - Original Draft.
Pedro Igor Bezerra Batista: Visualization, Methodology,
and Writing - Original Draft.
8. Data availability statement
The authors confirm that the data supporting the findings
of this study are available within the article [and/or] its
supplementary materials.
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