Hindawi Publishing Corporation
Advances in Civil Engineering
Volume 2014, Article ID 970393, 16 pages
http://dx.doi.org/10.1155/2014/970393
Research Article
Case Study of Remaining Service Life Assessment of a Cooling
Water Intake Concrete Structure in Indonesia
M. Sigit Darmawan, Ridho Bayuaji, N. A. Husin, and R. B. Anugraha
Civil Engineering Diploma Program, Institut Teknologi Sepuluh Nopember (ITS), Surabaya 60111, Indonesia
Correspondence should be addressed to M. Sigit Darmawan; msdarmawan@ce.its.ac.id
Received 8 August 2014; Revised 10 October 2014; Accepted 10 October 2014; Published 11 November 2014
Academic Editor: Andreas Kappos
Copyright © 2014 M. Sigit Darmawan et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
This paper deals with the assessment of remaining service life of a cooling water intake concrete structure (CWICS) subjected
to corrosion due to chloride attacks. Field and laboratory tests were performed to determine the current existing condition of the
structure. Both destructive and nondestructive tests were employed to obtain the parameter needed for the assessment. Based on the
current condition and test results, structural analysis was carried out and the remaining safety factor of CWICS was determined.
From the analysis, it was found that most concrete elements of CWICS had safety factor greater than unity and might fulfil its
intended service life up to the year 2033. However, fewer elements require immediate strengthening to extend their service life.
1. Introduction
Corrosion of reinforcing steel due to chloride attack is
considered to be the primary cause of concrete deterioration
of reinforced concrete structure [1]. This factor combined
with poor practice in detail design, bad supervision, and
bad construction execution lead to early deterioration of
concrete structures. Concrete structures built 30–40 years ago
often do not comply with the present day and more modern
code requirement for durability. For example, most of the
present day concrete codes specify that the minimum cover
for concrete structures built in marine environment is 65 mm
[2], whereas the corresponding minimum concrete cover
during that time is around 50 mm. Furthermore, theoretical
foundation of chloride penetration in concrete structure
was not yet fully developed and well understood at that
time. This lack of knowledge and understanding on concrete
deterioration mechanism lead to nonintended faulty concrete
practices. Therefore, it is not surprising that older concrete
structures often has durability problem before their design
life has expired.
It is also expected for concrete structures built in a tropical
country such as Indonesia to have higher corrosion rate than
that of concrete structures built in temperate or cold region
[3]. This higher corrosion rates are caused by higher average
temperature and higher humidity experience by concrete
structures along the years. Furthermore, workmanship and
construction practice in Indonesia is not as good as those in
a developed country. All of these factors may lead to early
deterioration of concrete structures and shorten the service
life of concrete structure.
2. Case Study
This paper presents a study of remaining life assessment
[4] of cooling water intake concrete structure (CWICS) at
Indonesia. The study is comprised of field and laboratory test
and followed by analytical study. CWICS has been in service
for 19 to 33 years and subject to continues chloride attack from
nearby sea. Therefore, it almost reaches its design service
life of 30 years. In addition, part of CWICS also subjects to
high temperature from the discharge cooling water from the
factory. This higher temperature can increase corrosion rate
of steel rebar in concrete [5]. All of these conditions may
shorten the service life of CWICS and endanger the factory
operation. CWICS has an important role in gas production
factory as it supplies cooling sea water needed by the factory.
At present, some parts of CWICS have shown some signs
of damages, such as staining, rusting, cracking, spalling,
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Figure 1: Cracking of concrete plate (slab) of CWICS.
Figure 2: Front view of CWICS.
and delamination of concrete, see Figure 1. These damages
indicate that the chlorides may have already penetrated
concrete cover, reached rebar level, and accumulated to
threshold level chloride concentration to initiate corrosion.
The corrosion may have reduced rebar cross-section and lead
to a reduced strength capacity of some structural elements
of CWICS. If this condition is not rectified soon, it may
endanger the whole structure of CWICS and shut down the
factory operation. The shutdown of the factory can lead to
significant loss of revenue to factory owner.
The purpose of this study can be summarized as follows:
achieve this goal, the following steps and tests were employed
in this study.
(i) determine current existing condition of CWICS;
(ii) determine remaining life of CWICS;
(a) determine the safety factor of CWICS at year
2013;
(b) determine the safety factor of CWICS at year
2033.
3. Structural Configuration of Cooling Water
Intake Concrete Structure
Cooling water intake concrete structure (CWICS) is made
of concrete structure supported by steel piles. The concrete
structure of CWICS comprises plate (slab), beam, and wall
elements. A steel frame is installed on the top of CWICS
for a crane operation (see Figure 2). In addition, a number
of machines for pumping sea water are stationed on top of
the concrete structure. Most of these machines run for 24
hours without stopping. CWICS consists of 4 trains, which
has almost similar structural configuration. These are trains
A/B, C/D, E/F, and G/H, built in 1977, 1982, 1987, and 1995,
respectively. These trains were built by different contractors.
4. Methodology
To determine remaining service life of CWICS, the current
condition of CWICS needs to be investigated and rate of
deterioration needs to be determined. The ultimate goal of
this study was to determine whether CWICS can fulfill its
intended service life up to 2033 without strengthening. To
(i) Collect information regarding design criteria from
available document and as-built drawing and any
changes might occur during service period.
(ii) Determine current concrete density and concrete
compressive strength of CWICS.
(a) Compression test of core-drilled concrete sample.
(b) Ultrasonic pulse velocity (UPV) test.
(c) Hammer test.
(d) Porosity test.
(iii) Determine carbonation depth.
(a) Phenolphthalein test.
(iv) Determine yield strength of rebar and remaining steel
rebar thickness.
(a) Tension test of rebar samples taken from coredrilled concrete samples.
(b) Thickness loss measurement of corroded rebar.
(v) Determine chloride content and pH of the concrete at
different depth.
(a) Chloride content test from core-drilled concrete
samples.
(b) pH test.
(vi) Determine chloride and sulphate contents of seawater.
(vii) Determine probability of corrosion of rebar.
(a) Half-cell potential measurement.
(viii) Structural and load modeling of CWICS using available finite element. program to determine the internal
forces.
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(ix) Determine rate of concrete deterioration.
(a) Concrete cover depth measurement.
(x) Determine present capacity of structural element of
CWICS.
(xi) Determine remaining service life of CWICS.
At present paper, only concrete structure of CWICS
is considered. Steel piles that supported CWICS will be
discussed in another study. It must be mentioned here that,
during field tests, factory operation must not be interrupted.
Further, safety measure in the studied area was very tight and
only limited access was given to do the field test. Therefore,
the number and the location of tests performed were rather
limited. To compensate this deficient, data interpretation of
the tests was combined with engineering judgment to predict
remaining service life of CWICS. Due to limited number of
data obtained from this study, only deterministic approach
was discussed in this paper.
4.1. Determine Current Concrete Condition of CWICS. Information regarding the design compressive concrete strength
of CWICS can be found in the available as-built drawing and
document specification. The specified concrete strength was
28 MPa with a maximum water-cement ratio of 0.4 and used
type II cement. This concrete strength is slightly lower than
the present day minimum concrete strength requirement
for marine environment of 35 MPa. However, the actual
compressive strength achieved during construction was not
well documented. Therefore, this data must be obtained by
performing field and laboratory test. Four different tests were
used to estimate current concrete condition of CWICS. These
included compression test of core-drilled concrete sample,
hammer test, UPV test, and porosity test. The most accurate
method to determine concrete strength is compression test
of core-drilled concrete sample. However, this destructive
method is very expensive to perform and create permanent
defect at the existing structure (see Figure 3). Therefore, this
method was combined with nondestructive test, such as
hammer and UPV test to get more data for concrete strength
indication and homogeneity. Hammer and UPV tests were
performed for each location of core-drilled concrete sample
and other locations. If the number of data is sufficient, a correlation chart between these tests and compressive strength can
be derived. Using this chart, the concrete strength can then
be inferred both from hammer and UPV tests. However, as
shown later in the next section, a good correlation factor was
not always obtained between these tests due to a number of
reasons.
Table 1 gives the number of concrete core-drilled samples
for each train. This table shows that more samples are
taken from older train than newer one. This approach was
employed as older train has shown more sign distress than
newer train. The location of core-drilled sample at train A/B
is shown in Figure 4. A similar pattern of sampling was also
used for other trains. To avoid rebar in the concrete, the
location of core-drilled was first checked using rebar detector
before any drilling operation commenced. However, out of
Figure 3: Core-drilled sample.
Table 1: Number of concrete core-drilled sample.
Train
A/B
C/D
E/F
G/H
Total
Numbers
5
4
3
3
15
Table 2: Compressive strength of core-drilled sample.
No.
Code
Location
Compressive
strength (kg/cm2 )
1
2
3
4
5
6
7
8
9
10
Core 1
Core 2
Core 3
Core 6
Core 8
Core 9
Core 10
Core 11
Core 12
Core 14
Train A/B
Train A/B
Train A/B
Train C/D
Train C/D
Train C/D
Train E/F
Train E/F
Train E/F
Train G/H
222.13
246.63
279.66
408.35
401.70
377.76
373.76
351.93
397.65
411.01
fifteen core-drilled samples, only ten samples were successfully compression tested and five samples were broken during
the drilling process. The broken samples were examined and
it was found that cracks were formed in these samples. The
core-drilled samples were obtained from the top of CWICS as
the access from the other side was very limited and the factory
must operate at all times without stopping. The compressive
strength of core-drilled samples is given in Table 2.
Table 2 shows that the compressive strengths of coredrilled samples of train A/B are lower than the compressive
strength of core-drilled samples from the other trains. This
result may indicate that the concrete at this oldest train
has already experienced more strength degradation than
concrete at the other trains. The concrete strength at train
A/B is lower than the present day minimum concrete strength
requirement for marine environment (i.e., 350 kg/cm2 ) such
as stipulates in [2] and also lower than the specified concrete
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5800
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2650
5800
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5800
PIER
CL
5800
PIER
250
6000
Roadway
5500
PIER
250
2500
N
A
200
PIER
250
200
2075
C1
DWG.NO 32-E-M-209
Pipe support
TYP
CL
725
200
925
EL +4.45
(TYP)
Drain pipe
H.P.E. +3.25
(TYP)
3 0 pipe
drain
3250
EL +5.05
(TYP)
7810
strainer
4850
L.P. EL. 3.22
(TYP)
200
4
H
32-E-M-218
(SIM)
CL
7600
strainer
1254 CL
Protective
crub
EL +4.85
CL C.W. pumps
4350
925
3
Open
Open
Open
Open
Open
4
Open
Open
Open
Open
400 deep
trench
1750
Open
Open
Open
C3
1850
C5
EL +4.00
3700
C2
Open
Open
Open
Open
EL +4.04
(TYP)
EL +4.00
(TYP)
EL. +3.80
Open
Open
200
Open
Open
Open
3600
(control room slab)
Open
Open
Open
Open
Open
Open
2
Open
Open
Open
Open
Open
2 EL. +3.20
Open
EL +4.85
1680
H.p. EL. +3.85
12000
1850
C4
CL Trav screens
1 22000
Open
CL
2120
2100
9790
CL F.W. pumps
3950
Open
Open
Open
Open
Open
Open
2160
4000
TYP
2940
3 0 pipe drain
A
Figure 4: Core-drilled location at train A/B (Core 1/C1 up to Core 5/C5).
Figure 5: UPV test at train A/B.
Figure 6: Hammer test at train A/B.
strength of 280 kg/cm2 as found in as-built drawing. By comparison, the highest compressive strength was obtained at the
newest train G/H at 411.01 kg/cm2 . However, only one coredrilled sample has been successfully tested for this train. In
addition to concrete core drill, UPV and hammer tests were
performed as shown in Figures 5 and 6. The location of these
tests can be seen in Figures 7 and 8, respectively.
Table 3 shows the ultrasonic velocity and its corresponding compressive strength for all trains. This table shows that
almost all ultrasonic velocities in the concrete fall below
3000 m/s, except the ultrasonic velocity of cores 3 and 8.
Based on [6], these low ultrasonic velocities can be classified
as doubtful. These low readings of ultrasonic velocity are
possibly due to discontinuity that presents in the concrete
Advances in Civil Engineering
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5800
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6000
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5500
PIER
250
2500
N
A
200
PIER
250
200
2075
U1
DWG.NO 32-E-M-209
Pipe support
TYP
CL
725
200
925
EL +4.45
(TYP)
Drain pipe
H.P.E. +3.25
(TYP)
3 0 pipe
drain
3250
EL +5.05
(TYP)
7810
strainer
4850
L.P. EL. 3.22
(TYP)
200
U6
EL +4.85
925
CL C.W. pumps
4350
U9
4
H
32-E-M-218
(SIM)
CL
7600
strainer
1254 CL
Protective
curb
3
Open
Open
Open
Open
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4
U2
Open
Open
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3950
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400 deep
trench
1750
Open
Open
Open
U5
1850
U10
3700
EL +4.00
U11
U3
Open
Open
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(TYP)
EL. +3.80
Open
Open
200
Open
Open
Open
3600
(control room slab)
Open
Open
Open
Open
Open
Open
2
Open
Open
Open
Open
Open
2 EL. +3.20
Open
EL +4.85
U12
H.P. EL. +3.85
U7
12000
Open
Open
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1 22000
1850
U8
2120
2100
Open
CL
EL +4.00
(TYP)
1680
9790
Open
Open
Open
Open
Open
Open
Open
2160
U4
4000
TYP
2940
3 0 pipe drain
A
Figure 7: UPV test location at train A/B.
plate (slab) of CWICS. After a close examination of coredrilled samples in the laboratory, it was found that a 20 mm
nonshrinking grouting material was laid on top of concrete
plate to give additional protection against chloride environment. Because this material and the old concrete below have
different properties, discontinuity presents between them.
This discontinuity reduces the ultrasonic velocity in the
concrete. The ultrasonic pulse may be diffracted around the
discontinuities, therefore increasing the travel path and travel
time [7].
Table 3 indicates that core 1 drilled at train A/B gives the
lowest ultrasonic velocity of 1830 m/s. This lowest value corresponds with its lowest compressive strength of 222.13 kg/cm2 .
Similar trend is also found for train C/D where low compressive strength corresponds with low ultrasonic velocity.
However, this trend does not apply for train E/F where low
compressive strength gives high ultrasonic velocity. Table 3
also shows that the highest ultrasonic velocity of 3232 m/s is
found at core 8 with its corresponding compressive strength
of 279.66 kg/cm2 . As each train was built in different years
and used different concrete mixes, correlation chart between
UPV and compression strength for each train was derived
separately. The correlation chart is shown in Figures 9, 10, and
11 for train A/B, C/D, and E/F, respectively.
Figures 9 to 11 show that the best correlation between
ultrasonic velocity and compressive strength is found for
samples taken at train A/B, with a correlation factor (𝑅) of
0.997. On the contrary, Figure 11 shows an opposite trend
between these two tests at train E/F, where the highest
ultrasonic velocity gives a lower strength. Again this result
confirms that nondestructive test results should not be used
solely without destructive test as it may lead to wrong
interpretation.
Figure 12 shows a correlation chart between hammer
and compressive strength at train C/D. It gives a reasonable
correlation factor (𝑅) of 0.72089. However, if all hammer tests
for all trains are combined in one chart, the correlation factor
between hammer and compressive strength drops to 0.19884
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5800
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5800
CL
5800
CL CW pump
2650
5800
CL
5800
PIER
CL
5800
PIER
250
6000
Roadway
5500
PIER
250
2500
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A
PIER
250
200
2075
200
H1
DWGNO 32-E-M-209
Pipe support
TYP
CL
725
200
925
EL +4.45
(TYP)
Drain pipe
H.P.E. +3.25
(TYP)
3 0 pipe
drain
3250
EL +5.05
(TYP)
7810
strainer
4850
L.P. EL. 3.22
(TYP)
200
H40
H6
EL +4.85
925
CL C.W. pumps
4350
H9
4
H
32-E-M-218
(SIM)
CL
7600
strainer
1254 CL
Protective
crub
3
Open
Open
Open
Open
Open
4
H2
Open
Open
CL F.W. pumps
3950
Open
400 deep
trench
1750
Open
Open
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H5
1850
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EL +4.00
3700
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H3
Open
Open
Open
Open
EL +4.04
(TYP)
EL +4.00
(TYP)
Open
EL. +3.80
Open
200
Open
Open
Open
3600
(control room slab)
Open
H39
Open
Open
Open
Open
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2
Open
Open
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Open
1680
EL +4.85
H.P. EL. +3.85
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12000
1850
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CL
2120
2100
9790
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H4
4000
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2940
3 0 pipe drain
A
Figure 8: Hammer test location at train A/B.
Table 3: Compressive strength and ultrasonic velocity of coredrilled samples.
Number Code
1
2
3
4
5
6
7
8
9
10
Core 1
Core 2
Core 3
Core 6
Core 8
Core 9
Core 10
Core 11
Core 12
Core 14
Location
Compressive
strength (kg/cm2 )
Ultrasonic
velocity (m/s)
Train A/B
Train A/B
Train A/B
Train C/D
Train C/D
Train C/D
Train E/F
Train E/F
Train E/F
Train G/H
222.13
246.63
279.66
408.35
401.70
377.76
373.76
351.93
397.65
411.01
1830
2338
3232
2420
3002
2413
1842
2263
2008
2610
as shown in Figure 13. It must be mentioned herein that,
before hammer tests were performed, the hammer equipment
was calibrated first using standard anvil from the manufacturer. Further, the concrete surface was first grinded to obtain
flat surface. However, the rebound numbers obtained during
the test were lower than those available in the literature
and also gave lower correlation factor between hammer and
compressive strength [8]. One possible explanation of this
condition to occur was that the hammer tests were performed
on the top side of concrete plate. As discussed earlier in the
section, it was found that, during the service life of CWICS,
a 20 mm non-shrinking grouting material was laid on top of
the concrete plate. This material does not contain any coarse
aggregate and therefore leads to lower rebound number of
hammer tests. Hammer test performed on the other elements
such as beam and wall elements gave a higher rebound
number than that obtained from concrete plate element.
However, no concrete drill samples were taken from beam
and wall elements as field condition did not allow the drilling
process to be executed on these elements.
Concrete porosity is the major factor that influences both
strength and durability of concrete structure. Concrete with
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400
280
390
Compression strength (kg/cm2 )
Compression strength (kg/cm2 )
270
260
250
240
350
1800
Ultrasonic velocity (m/s)
2000
2100
Ultrasonic velocity (m/s)
y = 149.41 + 0.040568x R = 0.99739
y = 501.95 − 0.062572x R = 0.58026
2000
2200
2400
2600
2800
3000
3200
3400
Figure 9: Correlation between UPV and compression strength for
train A/B.
410
410
405
405
400
395
390
385
2200
2300
400
395
390
385
380
380
375
2400
1900
Figure 11: Correlation between UPV and compression strength for
train E/F.
Compression strength (kg/cm2 )
Compression strength (kg/cm2 )
370
360
230
220
1800
380
2500
2600
2700
2800
2900
Ultrasonic velocity (m/s)
3000
3100
y = 356.16 + 0.015232x R = 0.32005
375
29
30
31
32
33
34
35
Rebound number
y = −13.465 + 0.11432x R = 0.72089
Figure 10: Correlation between UPV and compression strength for
train C/D.
Figure 12: Correlation between hammer and compression strength
for train C/D.
high porosity has a low concrete strength and low durability.
A number of methods can be used to determine the porosity
of concrete such as saturation method, helium pycnometry
and mercury intrusion porosimetry. For this study, porosity
test was performed using vacuum saturation apparatus [9].
The result of this test is presented in Table 4. This table shows
that most of the sample has a porosity less than 10%, except
for the sample taken from core 1. Core 1 has the highest
porosity of 11.5%. This value also corresponds with its lowest
compressive strength of all samples. By comparison, core 6
has the lowest porosity at 4.3%, but it gives only the second
highest value of all compressive strength.
Compared with the available data in the literature [10,
11], the porosity of concrete given in Table 4 is lower for
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450
Compression strength (kg/cm2 )
450
Compression strength (kg/cm2 )
400
350
300
250
200
28
400
350
300
250
200
29
30
31
32
33
34
35
4
5
6
7
8
9
Porosity (%)
10
11
12
y = 496.9 − 18.797x R = 0.53944
Figure 14: Correlation between porosity and compression strength
for all trains.
Rebound number
y = 28.479 + 0.0077793x R = 0.19884
Figure 13: Correlation between hammer and compression strength
for all trains.
Table 4: Porosity test of concrete core-drilled samples.
Code
Train
Porosity
Compressive strength
(kg/cm2 )
Core 1
Core 2
Core 6
Core 9
Core 10
Core 14
A/B
A/B
C/D
C/D
E/F
G/H
11.5%
7.8%
4.3%
9.8%
8.3%
8.4%
222.13
246.63
408.35
377.76
373.76
411.01
the same concrete strength. The data in the literature shows
that for concrete strength of 30 to 40 MPa, the porosity
of concrete is found around 15 to 20%. On the contrary,
data in Table 4 shows concrete porosity of 4.3–11.5% but
with corresponding max concrete strength of only 40 MPa.
It must be mentioned herein that all the available data in
the literatures was mostly taken at 28–90 days old, while
porosity data presented herein was taken after 19–33 years
old. It appears that older concrete gives lower porosity than
younger concrete but without significant strength gains.
Figure 14 shows the correlation chart between porosity
and compressive strength for all trains. Compared with
Figure 13, porosity has a better correlation to compressive
strength than hammer test, having a correlation factor of
0.54. This result again confirms that destructive test such as
porosity test has a better accuracy than nondestructive test
such as UPV test. However, porosity test requires the samples
to be taken from an existing structure and therefore it is
expensive to perform.
Figure 15: Carbonation test of core-drilled samples.
4.2. Determine Carbonation Depth. After concrete coredrilled sample was obtained, the cylinder specimen was
then straight away tested for depth of carbonation. Depth of
carbonation was checked using a solution of phenolphthalein
indicator that appears pink in contact with alkaline concrete
with pH values in excess of 9 and colourless at lower levels of
pH [12]. This test is most commonly performed by spraying
the indicator on freshly exposed surfaces of concrete broken
from the structure or on split cores. All of the fourteen
samples changed their color to pink as shown in Figure 15.
This showed that no concrete carbonation was detected for
CWICS up to the present, despite the fact that some of the
trains have been in service for more than 30 years.
4.3. Determine Yields Strength of Rebar and Remaining Steel
Rebar Thickness. Yield strength of rebar can be obtained from
available as-built drawing. However, to get a more accurate
data of yield strength, tensile test was performed. Reinforcing
bars extracted during concrete core-drilled were used as
specimen samples. Four samples of rebar were successfully
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Table 5: Corrosion thickness of rebar.
Number
1
2
3
Code
Core 3
Core 8
Core 15
Rebar diameter
𝐷 19
𝐷 19
𝐷 19
Train
A/B
C/D
G/H
Corrosion thickness
10∼20 𝜇m
20∼50 𝜇m
3∼8 mm
Corrosion rate (mm/year)
0.0003–0.0006
0.0007–0.0017
0.1875–0.5
Microstructure
Pearlite and Ferrite
Pearlite and Ferrite
Pearlite and Ferrite
80
70
Tension (KN)
60
50
40
30
Figure 18: Microstructure with 500x magnification of rebar taken
from core 15.
20
10
0
0
5
10
15
20
25
Strain (%)
Figure 16: Force and displacement of rebar from tension test.
Figure 17: Corrosion thickness of 3 ∼ 8 mm taken from core 15.
tensile tested. The result of one of tensile test is shown in
Figure 16. The yield strength of rebar was found between 533
and 560 MPa, whereas their corresponding ultimate strengths
were found between 759 and 878 MPa. This yield strength was
higher than that of the specified yield strength of 400 MPa.
The loss of rebar thickness due to corrosion was measured
using Olympus metallurgical camera and Union metallurgical microscope, as shown in Figures 17 and 18. The rebar
samples for this test were obtained from concrete coredrilled. Table 5 shows the corrosion thickness of the rebar
for each train. This table shows that train E/F has the highest
corrosion rates of 0.1875–0.5 mm/year. This corrosion rate is
much higher than the corrosion rate of trains A/B and C/D
at 0.0003–0.0006 and 0.0007–0.0017 mm/year, respectively.
These two trains have almost negligible corrosion. The higher
corrosion rate observed at train E/F is most likely due to local
incidence such as local low concrete compaction. Therefore,
this value should not be used as a representative value of
the steel corrosion rate of train E/F. Furthermore, as only
one sample was taken for this test for each train, this result
should be used cautiously and should be compared with other
forms of tests or formulae to determine the corrosion rate of
CWICS. The representative value of corrosion rate of each
train will be discussed and determined in Section 4.8.
4.4. Determine Depth and Chloride Content and Concrete
pH in the Concrete. After compression test of core-drilled
sample, the debris from this test was chloride tested. Three
different depths were used to measure the chloride content,
that is, 0.0, 2.5, and 5.0 cm from concrete surface. At the same
time, the pH of the concrete was also measured. The results of
chloride test and pH test are presented in Figures 19 and 20,
respectively.
Figure 19 shows that the chloride content measured by
weight of concrete (in %) at concrete surface for all samples
is very close to one another, except sample taken from core
15. Core 15 drilled at train G/H shows the highest chloride
content at all measured depths. This highest chloride content
correlates with its highest thickness loss of rebar as presented
in Table 5. Figure 19 also indicates that all of the samples
have a very similar chloride content of 0.01% at concrete
depth of 50 mm, where the rebar is located. This value can
be compared with the chloride threshold level to initiate
corrosion of 0.025% such as stipulates in Indonesia Concrete
Building Code [2].
Figure 20 shows that the concrete pH is relatively constant
as the depth from concrete surface increases. The lowest pH is
10
Advances in Civil Engineering
Table 6: Main aggressive element in sea water.
0.20
Chloride content (%)
0.15
Parameter
Unit
pH
Sulphate
Chloride
mg/L
mg/L
Sample
1
7.77
1600
14250
2
7.82
1585
14240
0.10
0.050
0.0
0
1
2
3
Depth (cm)
Core 1
Core 3
Core 6
Core 9
Core 11
Core 15
4
5
4.5. Determine Chloride and Sulphate Content of Sea Water.
Sea water surrounding CWICS was tested to determine the
concentration of its main aggressive elements that influence
the degree of chloride attack. Two samples were tested and
the results are presented in Table 6. This table shows that
the highest chloride and sulphate content of the sea water
is 14250 mg/L and 1600 mg/L, respectively. These values are
lower than the chloride and sulphate content of sea water
found in the Persian Gulf [13] at 26800 mg/L and 3460 mg/L,
respectively. These lower contents are possibly caused by high
water rainfall in Indonesia than that in the Persian Gulf.
Figure 19: Chloride content at different depths.
13.0
pH
12.5
12.0
11.5
11.0
0
1
Core 1
Core 3
Core 9
2
3
Depth (cm)
4
5
Core 6
Core 11
Core 15
Figure 20: pH value at different concrete depth.
11.25 at concrete surface and 11.35 at 5 cm depth. This indicates
that the concrete is still in a very high alkaline condition
and has no experience pH reduction due to corrosion attack.
This result corroborates with previous result (see Figure 19)
which indicate that concrete corrosion has not yet initiated
at CWICS. Note that core 15 which has the highest chloride
content also has the lowest pH at concrete depth of 0.0 and
25 mm and the second lowest pH at concrete depth of 50 mm.
Core 15 also has the highest thickness loss of rebar as shown
in Table 5.
4.6. Determine the Probability of Corrosion of Rebar. The risk
of corrosion of rebar in concrete can be estimated using
half-cell potential test. Half-cell potential test is simple,
cheap, and nondestructive. The electrode used for this test
is copper/copper sulphate electrode (CSE). The test was
performed based on ASTM [14]. The result of this test is
summarized in Table 7.
Table 7 shows that the most negative potential of rebar
(i.e., −0.520 mV) was found at train C/D, followed by trains
A/B, E/F, and G/H. All potential readings indicate that the
potential of rebar is already in negative side. According to
ASTM C-876, the potential reading less than −350 mV means
that the probability of corrosion of rebar is greater than 90%.
If the result of potential measurement is combined with pH
test (i.e., −0.520 mV and pH 11.35) and then plotted using
Pourbaix diagram, then the corrosion tendency of rebar can
be seen in Figure 21. This figure shows that the concrete of
CWICS is still in noncorroding stage (at passivation zone).
This result confirms the result of corrosion rate measurement
discussed in Section 4.3 which indicates that the train has
almost negligible corrosion rate as found in cores 3 and 8.
However, this condition may turn in to corroding stage if the
concrete pH decreases to less than 10.0.
4.7. Structural and Load Modelling of CWICS. Structural and
load modeling of CWICS was performed using SAP 2000
to determine the internal forces of CWICS. These internal
forces were then compared with the remaining capacity
of CWICS’s structural elements. The remaining capacity
of CWICS has decreased from its initial design capacity
due to rebar corrosion. If ratio of the capacity of concrete
element to the internal force of the element (defined herein as
safety factor) is greater than unity, the element is considered
in a safe condition. However, if this ratio reaches unity
or less, the element theoretically has failed and has to be
strengthened to achieve the minimum safety of 1.0. Note that
the redundancy effect of this highly indeterminate structure
Advances in Civil Engineering
11
2.0
58.5
54.0
49.5
45.0
40.5
36.0
31.5
27.0
22.5
18.0
13.5
9.0
4.5
0.0
1.5
Passivation
1.0
Corrosion
E (V)
0.50
0.0
Corrosion
Figure 23: Bending moment distribution of train A/B.
−0.50
Table 7: Half-cell potential measurement of rebar.
−1.0
Immunity
−1.5
0
Number
4
8
12
16
pH
Figure 21: Pourbaix diagram of rebar.
Figure 22: Structural model of train A/B.
was not considered in this analysis when safety factor of
element was determined. Therefore, it must be mentioned
here that the actual safety factor of CWICS may be higher
than the calculated safety factor obtained from this analysis.
Figure 22 shows structural model of CWICS of train A/B.
The structure comprises beam, plate (slab), and wall elements.
Loads considered in this analysis were dead, live, equipment, and earthquake load. To get the maximum internal
forces in the concrete element, different load combination
is determined based on Indonesia Concrete Code [2]. The
distribution of bending moment of train A/B due to dead and
live is shown in Figure 23.
4.8. Determine Rate of Deterioration. Rate of concrete deterioration or corrosion rate can be determined by two following
methods. These are
(i) direct method;
(ii) indirect method.
Direct method of corrosion rate estimation can be performed by measuring either weight loss or thickness loss of
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Train A/B Train C/D Train E/F Train G/H
Readings (mV)
−0.380
−0.120
−0.080
−0.090
−0.330
−0.130
−0.090
−0.070
−0.220
−0.090
−0.120
−0.100
−0.370
−0.030
−0.100
−0.070
−0.180
−0.120
−0.110
−0.080
−0.220
−0.090
−0.130
−0.100
−0.120
−0.130
−0.150
−0.120
−0.130
−0.280
−0.130
−0.060
−0.180
−0.140
−0.100
−0.080
−0.200
−0.140
−0.220
−0.160
−0.150
−0.120
−0.180
−0.240
−0.210
−0.190
−0.140
−0.180
−0.050
−0.200
−0.050
−0.270
−0.050
−0.320
−0.050
−0.270
−0.100
−0.270
−0.270
−0.340
−0.510
−0.520
−0.520
Minimum −0.380
−0.520
−0.150
−0.120
Maximum −0.050
−0.030
−0.080
−0.060
Average
−0.177
−0.226
−0.112
−0.086
rebar. This method requires the steel sample to be extracted
from existing structure. Table 5 shows the result of direct
method of corrosion rate measurement of CWICS. This table
shows that trains A/B and C/D have much lower corrosion
rate than the newer train G/H. In this case, this methods
yield a contradictory results with actual field condition of
CWICS, which shows that older train shows more sign of
distress than newer train. For this reason, indirect method of
12
Advances in Civil Engineering
Table 8: Concrete cover thickness.
Concrete cover (mm)
Location
Train A/B
Train C/D
Train E/F
Train G/H
Min
Average
50.0
32.5
53.0
44.0
83.3
65.0
74.0
61.7
corrosion rate measurement was employed in this study and
direct method was mainly used for comparison purpose only.
Indirect method of corrosion rate estimation was performed by using empirical formulae available in many
literatures. These formulae were developed through three
decades of research on corrosion mechanism and will be
discussed briefly in the following paragraph. To estimate
concrete rate of deterioration using indirect method, the
actual concrete cover needs to be measured. The thickness of
concrete cover determines the resistant of concrete structure
against corrosive agent such as chloride. To initiate corrosion,
chloride must penetrate concrete cover, reach the rebar level,
and accumulate to chloride threshold level. In this study,
concrete cover was measured using Profometer 5+. The result
of this test is summarized in Table 8. Note that based on the
available document, the specified concrete cover was 75 mm.
Table 8 shows that the lowest average concrete cover is
61.7 mm found in train G/H. This value can be compared
with the minimum cover thickness as specified in Indonesian
Concrete Standard [2], which stipulates that the minimum
cover for corrosive environment is 65 mm. However, all the
minimum cover found during the test does not comply with
the present day code requirement. The actual concrete cover
found during this test can be also used as indication of quality
control during construction phase. It is very surprising that
the oldest train (train A/B) shows a better quality in terms
of cover thickness than the newer trains. Train A/B has the
highest average concrete cover and the highest minimum
concrete cover at 83.3 mm and 50.0 mm, respectively.
Deterioration stage of reinforced concrete structure subjected to corrosion can be divided in two stages [15]:
(i) corrosion initiation;
(ii) corrosion propagation.
The time required for the chloride concentration at the
steel surface to reach the threshold chloride concentration
needed to destroy the passive layer of the steel is defined
as corrosion initiation. The second stage is called corrosion
propagation, where steel reinforcing bar corrodes causing loss
of area (metal loss) and reduces flexural and shear strength.
Corrosion initiation can be determined using Fick’s second law [16] as
𝑇𝑖 (𝐶𝑜 , 𝐶th , 𝐷, 𝑑𝑐 ) =
𝑑𝑐 2
4𝐷 [erf−1 (1 − (𝐶th /𝐶𝑜 ))]
2
,
(1)
where 𝐶𝑜 = chloride content at concrete surface, 𝐶th =
threshold chloride content to initiate corrosion, 𝐷 = concrete
diffusion coefficient, 𝑑𝑐 = concrete cover, and erf = the error
function.
Chloride content at concrete surface (𝐶𝑜 ) has been
determined from chloride test discussed at Section 4.4, while
threshold chloride content to initiate corrosion (𝐶th ) is
prescribed in most concrete codes or used empirical values
found in the literature. The average and minimum value of
concrete cover shown in Table 8 can be used in corrosion
initiation calculation to obtain two scenarios of deterioration,
that is, average and worst case scenarios.
The concrete diffusion coefficient in (1) can be estimated
using empirical formulae [17] as
𝐷 = 10−10+(4.66w/c) ,
w
27
=
,
c
𝑓cyl + 13.5
(2)
where w/c is the water cement ratio and 𝑓cyl
is the cylinder
compressive strength from core-drilled concrete.
Corrosion propagation is determined using empirical
formula [15] as
𝑖corr =
27.0 (1 − w/c)−1.64
(𝜇A/cm2 ) ,
𝑑𝑐
(3)
where 𝑖corr is corrosion rate in 𝜇A/cm2 . Note that a corrosion
current density of 1 𝜇A/cm2 is equal to a steel section loss of
11.6 𝜇m/year [18].
The above formulae is used to predict the corrosion rates
in concrete structures for mean relative humidity (RH) of
80% and mean temperature of 20∘ C. To obtain corrosion rate
at different temperature, the following formulae [5] can be
utilized:
𝑖corr (𝑡) = 𝑖corr-20 [1 + 0.073 × (𝑡 − 20)] ,
(4)
where 𝑖corr (𝑡) = corrosion rate temperature > 20∘ C, 𝑖corr-20 =
corrosion rate temperature 20∘ C, and 𝑡 = temperature (∘ C).
At the present study, the average temperature used was
31∘ C. Using this value and (4), the corrosion rate increases
around 80% compared with corrosion rate at 20∘ C.
Assuming general uniform corrosion, as displayed in
Figure 24, the diameter reduction of reinforcing bar (rebar)
due to corrosion can be estimated as
Δ𝐷 (𝑇𝑜 ) = 0.0232 × 𝑖corr × 𝑇𝑜 .
(5)
The remaining area of rebar can then be determined as
𝐴 𝑠 (𝑇𝑜 ) =
𝜋
2
(𝐷 − 0.0232 × 𝑖corr 𝑇𝑜 ) ,
4 𝑜
(6)
where 𝑇𝑜 is time measured after corrosion initiation.
Using (1) to (6), concrete deterioration then can be
determined. Two scenarios were used for this study:
(a) worst case condition scenario;
(b) average case condition scenario.
Advances in Civil Engineering
13
Table 9: Corrosion initiation time and concrete deterioration rate.
Train
A/B
C/D
E/F
G/H
Scenarios
Worst case Average case Worst case Average case Worst case Average case Worst case Average case
Built (year)
1977
1982
1987
1995
Operated (year)
1979
1984
1989
1997
22.2
24.9
37.8
39.6
35.1
37.4
41.1
41.1
Compressive strength 𝑓 𝑐 (MPa)
Cover thickness (mm)
50
83
32.5
65
53
74
44
61.7
Corrosion initiation (year)
1.82
13.91
5.73
35.56
10.25
26.13
6.99
26.13
Corrosion rate (mm/year)
0.229
0.100
0.118
0.056
0.081
0.053
0.079
0.056
Remaining capacity at 2013 (%)
44%
83%
77%
100%
90%
100%
94%
100%
Remaining capacity in 20 year (%) 21%
67%
59%
93%
77%
92%
80%
92%
Do
Figure 24: General uniform corrosion.
In the worst case scenario, all parameters used in the
analysis were either the minimum or the maximum value
obtained from the test in order to get the fastest deterioration
of structure. For example, the minimum value was used for
concrete cover thickness and concrete strength parameter,
whereas the maximum value was used for chloride content
parameter. By contrast, average values of parameters were
used for the average case scenario. Table 9 summarizes the
results of analysis using these two scenarios. Note that
concrete strength used in this analysis is concrete strength
obtained from compressive test of concrete core-drilled
samples.
Table 9 shows that train A/B has the shortest corrosion
initiation time for the worst and average scenarios as it
has the lowest compressive strength. This train also has the
highest corrosion rate at around 0.229 mm/year for worst
case scenario and 0.1 mm/year for average case scenario,
respectively. It is interesting to compare these corrosion rates
with corrosion rates obtained using direct method as shown
in Table 5. The corrosion rate of train A/B using indirect
method for the two scenarios is higher than that obtained
from direct method, which gives corrosion rate of 0.0003–
0.0006 mm/year. Therefore, corrosion rate based on indirect
method yields more conservative results than that from direct
method. For this reason, the corrosion rate from indirect
method will be used for determining the remaining capacity
of CWICS.
Based on the above assumption, for the worst case
scenario, the remaining capacity of train A/B at 2013 is 44%
of the initial capacity. However, for the average condition
scenario, the-2013 capacity of train A/B is around 83% of
the initial capacity. This average condition appears to better
represent the actual train condition as up to now this train
is still in service and there is no indication of significant of
distress of the train.
Table 9 also indicates that, for average case scenario, the
remaining capacity of train C/D, E/F, and G/H at year 2013
is still 100% of their initial design capacities. By year 2033,
these remaining capacities have decreased to 93%, 92%, and
92%, respectively. By comparison, for worst case scenario the
remaining capacity of these trains at year 2013 are 77%, 90%,
and 94% of their initial design capacities, respectively. By year
2033, these remaining capacities reduce to 59%, 77%, and 80%
of their initial design capacity, respectively.
4.9. Determine Safety Factor. To better capture the current
condition of CWICS, the reduction of safety factor of different element of CWICS due to rebar corrosion against flexure
and shear action will be presented. Only the result of analysis
of train A/B will be discussed in the next section as this train
has the worst condition.
The safety factor of concrete element against flexure and
shear can be formulated as
SF =
𝜑𝑀𝑛 (𝑇𝑜 )
> 1.0,
𝑀𝑢
(7)
SF =
𝜑𝑉𝑛 (𝑇𝑜 )
> 1.0,
𝑉𝑢
(8)
where 𝑀𝑛 (𝑇𝑜 ) = nominal flexural capacity of concrete element at 𝑇𝑜 after corrosion has initiated, 𝑀𝑢 = flexural
moment due to factor load obtained from structural analysis,
𝑉𝑛 (𝑇𝑜 ) = nominal shear capacity of concrete element at 𝑇𝑜
after corrosion has initiated, and 𝑉𝑢 = shear due to factor load
obtained from structural analysis.
The capacity of concrete element against flexure and shear
at 𝑇𝑜 can be determined as
𝑀𝑛 (𝑇𝑜 ) = 𝐴 𝑠 (𝑇𝑜 ) × 𝑓𝑦 × 0.8 × 𝑑,
𝐴 V (𝑇𝑜 ) × 𝑓𝑦 × 𝑑
1
𝑉𝑛 (𝑇𝑜 ) = √𝑓𝑐 × 𝑏𝑤 × 𝑑 +
,
6
𝑠
(9)
(10)
where 𝐴 𝑠 (𝑇𝑜 ) = area of rebar section at time 𝑇𝑜 , 𝑓𝑦 =
yield strength of rebar, ℎ = height of section, 𝑓𝑐 = concrete
compressive strength, 𝑏𝑤 = width of section, 𝑑 = effective
14
Advances in Civil Engineering
1.6
3.00
1.4
2.50
Safety factor
Safety factor
1.2
1.0
0.8
2.00
1.50
0.6
1.00
0.4
1980
1990
Average case
Worst case
2000
2010
Year
2020
2030
2040
Figure 25: Safety factor for plate element with 600 mm depth and
reinforced with 19 mm diameter rebar at 150 mm spacing.
depth of section, 𝐴 V (𝑇𝑜 ) = area of shear reinforcement at time
𝑇𝑜 , and 𝑠 = spacing of shear reinforcement.
The area of rebar for flexure defined as 𝐴 𝑠 (𝑇𝑜 ) and for
shear defined as 𝐴 V (𝑇𝑜 ) can then be determined using (6).
For the purpose of this study, the safety was determined at
year 2013 and year 2033 using (7) to (10). Figure 25 shows
the reduction of safety factor for concrete plate element with
600 mm depth and reinforced with 19 mm rebar diameter at
150 mm spacing.
Figure 25 indicates that, for average case scenarios, the
safety factor of 600 mm plate element decreases from 1.48
to 1.06 at year 2013 and to 0.82 at year 2033, respectively.
By comparison, for worst case scenarios, the safety factor
decreases from 1.48 to 0.57 at year 2013 and to 0.21 at year
2033, respectively. Therefore, this element requires immediate
strengthening as the safety factor already approaches 1.0 at
year 2013.
Figure 26 shows the reduction of safety factor for concrete
wall element with 600 mm depth and reinforced with 22 mm
diameter rebar at 150 mm spacing. This figure indicates that
for average case scenarios, the safety factor of 600 mm wall
element decreases from 2.54 to 1.95 at year 2013 and to
1.62 at year 2033, respectively. By comparison for worst case
scenarios, the safety factor decreases from 2.54 to 1.20 at year
2013 and to 0.58 at year 2033, respectively. Thus, this element
does not require immediate strengthening as the safety factor
is still greater than 1.0 at year 2013 for both scenarios.
Figure 27 shows the reduction of safety factor for beam
element with 500 mm × 800 mm cross-section and reinforced
with 4D28 mm diameter rebar against flexure. This figure
indicates that, for average case scenarios, the safety factor
of the beam decreases from 2.46 to 1.94 at year 2013 and to
0.500
1970
1980
1990
2000
2010
2020
2030
2040
Year
Average case
Worst case
Figure 26: Safety factor for wall element with 600 mm depth and
reinforced with 22 mm diameter rebar at 150 mm spacing.
2.50
2.00
Safety factor
0.2
1970
1.50
1.00
0.500
1970
1980
1990
2000
2010
Year
2020
2030
2040
Average case
Worst case
Figure 27: Safety factor for beam element with 500 mm × 800 mm
cross-section reinforced with 4D28 mm diameter rebar against
flexure.
1.65 at year 2033, respectively. By comparison, for worst case
scenarios, the safety factor decreases from 2.46 to 1.33 at year
2013 and to 0.81 at year 2033, respectively. Thus, this beam
does not require immediate strengthening as the safety factor
is still greater than 1.0 at year 2013.
Advances in Civil Engineering
15
5. Conclusions
4.50
The main conclusions drawn from this study can be summarized as follows.
Safety factor
4.00
(i) From field and laboratory tests, no significant corrosion activity has been found at CWICS. Most of
the reinforcing bars were still in a relatively passive
condition as concrete surrounding the reinforcing
bars was still in a high alkaline stage. Furthermore,
the chloride level at rebar position was found around
0.01% by weight of concrete. This value was still below
chloride threshold level to initiate corrosion given in
SNI-03-2847 at 0.025%.
3.50
3.00
(ii) From compressive test of core-drilled sample, train
A/B has the lowest average strength of all samples.
However, in terms of cover thickness, train A/B has
the highest cover thickness of all trains.
2.50
2.00
1970
1980
1990
2000
2010
Year
2020
2030
2040
Average case
Worst case
Figure 28: Safety factor for beam element with 500 mm × 800 mm
cross-section and shear reinforced with 2D12 mm diameter rebar
with 150 mm spacing against shear.
Figure 28 shows the reduction of safety factor for beam
element with 500 mm × 800 mm cross-section and shear
reinforced with 2D12 mm diameter rebar with 150 mm spacing against shear. This figure indicates that, for average case
scenarios, the safety factor of the beam decreases from 4.36
to 3.39 at year 2013 and to 2.97 at year 2033, respectively.
By comparison, for worst case scenarios, the safety factor
decreases from 4.36 to 2.48 at year 2013 and to 2.24 at
year 2033, respectively. Thus, this beam does not require
immediate strengthening as the safety factor is still greater
than 1.0 at year 2013.
It should be mentioned here that the remaining life
assessment of concrete structure due to corrosion attack also
has some limitations. Some of the models used in the analysis
are derived based on idealized condition. For example, the
assumption used for corrosion initiation model based on
Fick’s second law given in (1) may not be in agreement with
the actual service conditions. Fick’s second law assumes that
concrete is homogeneous material and relative in moist condition (saturated). In reality, concrete cover is generally not
saturated with water, concrete is a nonhomogeneous material
due to the presence of microcracking, interconnected pores,
and aggregated particles, and the diffusion coefficient 𝐷 may
change with time due to hydration progress [19]. Therefore,
the remaining life assessment of reinforce concrete structure
should be combined with engineering judgment and should
be validated with the actual field condition. Further, the
remaining life assessment should be performed every 5–
10 years as conditions may change significantly than those
predicted by available deterioration model.
(iii) Due to its lowest compressive strength obtained from
compression test of core-drilled sample, train A/B has
the highest corrosion rate for all trains.
(iv) Based on the available data compiled from the tests,
two different scenarios were used to estimate the
remaining life of CWICS. Using this approach, the
average case scenario represented closer to the actual
condition than that of the worst case scenario. The
analysis using worst case scenario for train A/B gives
the remaining capacity of 40% of the initial capacity.
This result does not represent the existing condition
of CWICS, which shows no significant sign of distress
up to the present. By contrast, using average case
scenario for train A/B gives the remaining capacity of
83% of the initial capacity.
(v) Structural analysis shows that the safety factor of most
concrete elements of CWICS was still higher than
unity up to year 2033. However, fewer elements were
also found to have safety factor approach to unity
at year 2013. These elements with low safety factor
require immediate strengthening to fulfill its intended
service life up to 2033.
Conflict of Interests
The authors declare that there is no conflict of interests
regarding the publication of this paper.
Acknowledgments
The authors greatly acknowledge the support of Material
Testing Laboratory of Civil Engineering Diploma Program
and the Institute of Research and Community Services of
Institut Teknologi Sepuluh Nopember (ITS), during field and
laboratory investigation of the study.
References
[1] A. Neville, “Chloride attack of reinforced concrete: an overview,” Materials and Structures, vol. 28, no. 2, pp. 63–70, 1995.
16
[2] “Tata Cara Perhitungan Struktur Beton untuk Bangunan
Gedung (Indonesia concrete building code),” SNI-03-2847,
2013.
[3] P. K. Mehta, Concrete in the Marine Environment, Taylor &
Francis, New York, NY, USA, 2003.
[4] H. S. Müller, M. Haist, and M. Vogel, “Assessment of the
sustainability potential of concrete and concrete structures
considering their environmental impact, performance and lifetime,” Construction and Building Materials, vol. 67, pp. 321–337,
2014.
[5] DuraCrete, Probabilistic Performance Based Durability Design of
Concrete Structures, 2000.
[6] BS-1881:Part203, Recommendations for Measurement of Velocity
of Ultrasonic Pulses in Concrete, British Standards Institution,
London, UK, 1986.
[7] ACI-Committee-228.1R-03, In-Place Methods to Estimate Concrete Strength Building, American Concrete Institute, Farmington Hills, Mich, USA, 2003.
[8] P. K. Mehta and P. J. M. Monteiro, Concrete: Microstructure,
Properties, and Materials, McGraw-Hill, 3rd edition, 2006.
[9] RILEM-Recommendations, “Absorption of water by immersion
under vacuum. Materials and structures,” in RILEM CPC 11.3,
vol. 101, pp. 393–394, 1984.
[10] X. Chen, S. Wu, and J. Zhou, “Influence of porosity on compressive and tensile strength of cement mortar,” Construction and
Building Materials, vol. 40, pp. 869–874, 2013.
[11] Y. Y. Kim, K. M. Lee, J. W. Bang, and S. J. Kwon, “Effect of W/C
ratio on durability and porosity in cement mortar with constant
cement amount,” Advances in Materials Science and Engineering,
vol. 2014, Article ID 273460, 11 pages, 2014.
[12] BS-EN-14630, Products and Systems for the Protection and
Repair of Concrete Structures. Test Methods. Determination of
Carbonation Depth in Hardened Concrete by the Phenolphthalein
Method, British Standards Institution, London, UK, 2006.
[13] M. Shekarchi, F. Moradi-Marani, and F. Pargar, “Corrosion
damage of a reinforced concrete jetty structure in the Persian
Gulf: a case study,” Structure and Infrastructure Engineering:
Maintenance, Management, Life-Cycle Design and Performance,
vol. 7, no. 9, pp. 701–713, 2011.
[14] ASTM-C-876, “Standard test method for half-cell potentials of
uncoated reinforcing steel in concrete,” in Annual Book of ASTM
Standards, vol. 03.02, pp. 11–16, 2006.
[15] K. A. T. Vu and M. G. Stewart, “Structural reliability of concrete
bridges including improved chloride-induced corrosion models,” Structural Safety, vol. 22, no. 4, pp. 313–333, 2000.
[16] J. Zhang and Z. Lounis, “Sensitivity analysis of simplified
diffusion-based corrosion initiation model of concrete structures exposed to chlorides,” Cement and Concrete Research, vol.
36, no. 7, pp. 1312–1323, 2006.
[17] M. G. Stewart and D. V. Rosowsky, “Structural safety and
serviceability of concrete bridges subject to corrosion,” Journal
of Infrastructure Systems, vol. 4, no. 4, pp. 146–155, 1998.
[18] D. A. Jones, “Localized surface plasticity during stress corrosion
cracking,” Corrosion, vol. 52, no. 5, pp. 356–362, 1996.
[19] J.-K. Kim, C.-Y. Kim, S.-T. Yi, and Y. Lee, “Effect of carbonation
on the rebound number and compressive strength of concrete,”
Cement and Concrete Composites, vol. 31, no. 2, pp. 139–144,
2009.
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