Fyp 1 progress report 2 half cell measurement for reinforce steel concrete %28 mohd izwan khalid%29
1. UNIVERSITI TENAGA NASIONAL
BACHELOR OF MECHANICAL ENGINEERING (HONS)
Author
Mohd Izwan Khalid b Mohd Supian
Code
Supervisor
Student ID
ME 087189
MPRB 412 (Progress Report 2)
Dr. Abdul Aziz
External Link
Malaysian Nuclear Agencies
Project Title
Assessment of reinforcing steels in concrete by using NDT (Half-Cell Potential)
Grade
Comments
Date hand out
Date received
1st Week
Date due in
Assessed date
16th December 2013
2. ASSESSMENT OF REINFORCING STEELS IN CONCRETE BY USING NDT (HALF-CELL POTENTIAL)
MPRB 412 - PROGRESS REPORT 2
REV NO : 000
DATE : 15 DECEMBER 2013
LIST OF CONTENT
ITEM
DESCRIPTION
PAGE
1
INTRODUCTION
1.1
Background study
1.2
Literature review
................................................
................................................
................................................
1
2
5
2
WORK COMPLETED
................................................
6
3
PROBLEMS
................................................
6
4
METHODOLOGY
4.1
Experiment 1 procedure
4.2
Experiment 2 procedure
................................................
................................................
................................................
7
7
9
5
APPARATUS
................................................
10
6
WORK SCHEDULE
................................................
12
7
REFERENCES
................................................
13
APPENDIX 1 - FYP 1 and 2 Gantt Chart
APPENDIX 2 – Mixture of concrete grade according to Nuclear Agencies
APPENDIX 3 – Result table
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3. ASSESSMENT OF REINFORCING STEELS IN CONCRETE BY USING NDT (HALF-CELL POTENTIAL)
MPRB 412 - PROGRESS REPORT 2
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DATE : 15 DECEMBER 2013
1 INTRODUCTION
Reinforcing steel in concrete is a type of steel which embedded into a particular building
structure and act as sort of bones to the building. The main idea of the steel is to retain
the surface tension of the concrete and without it the concrete would crack and degrade
to collapse. Basically the steel within stops it flexing and therefore holds it together. An
example of reinforced steel and its nature surrounding is transmits as per figure 1.
Figure 1 – Reinforced steel and operation of laying the concrete into the steel
The normal terms used to describe the steel is ‘rebar’. There is numerous type of steel rebar that
being used in the market and varies according to yield strength, ultimate tensile strength,
chemical composition, and percentage of elongation. The common type of steel rebar and its
application is outline in Table 1.
During purchasing of this item, the manufacturer normally will require the customer to provide
them with proper grade of rebar. The grade indicates the minimum yield strength of the bar is
ksi; (1000 psi). The normal preferences for rebar grade are to be 40, 60 and 75.
ASTM A82
ASTM A184/A184M
:
:
ASTM A185
:
ASTM A496
ASTM A615/A615M
ASTM A767/A767M
:
:
:
ASTM A934/A934M
ASTM A996
ASTM A1035
:
:
:
Specification for Plain Steel Wire for Concrete Reinforcement
Specification for Fabricated Deformed Steel Bar Mats for Concrete
Reinforcement
Specification for Welded Plain Steel Wire Fabric for Concrete
Reinforcement
Specification for Deformed Steel Wire for Concrete Reinforcement
Deformed and plain carbon-steel bars for concrete reinforcement
Specification for Zinc-Coated(Galvanized) Steel Bars for Concrete
Reinforcement
Specification for Epoxy-Coated Prefabricated Steel Reinforcing Bars
Rail-steel and axle-steel deformed bars for concrete reinforcement
Standard Specification for Deformed and Plain, Low-carbon,
Chromium, Steel Bars for Concrete Reinforcement
Table 1 – Several type of rebar that being used in the industry
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4. ASSESSMENT OF REINFORCING STEELS IN CONCRETE BY USING NDT (HALF-CELL POTENTIAL)
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1.1. Background study
This type of steel used as a structure in the concrete due to the fact that it’s
characteristic which is versatile, economical and its reputation as successful
construction material. However the corrosion problem that leads too catastrophic
tragedy towards reinforcing steel in concrete is a huge problem that being faced by
the civil engineers. An estimation of USD 150 billion worth of corrosion damage on
their interstate highway bridges is due to deicing and sea salt induced corrosion [1].
An earlier study on the probabilistic model for steel corrosion in reinforced concrete
structures explains that the corrosion can occur when the passive film; thin oxide
film that forms on the surface of the rebars due to the alkaline solution contained in
the pores of the hydrated cement paste, is removed or damaged [2]. Once the film
are removed there are 2 possible causes of corrosion which is carbonation; normally
in old and poorly constructed structure and the presence of chloride due to several
factors such as sea salt spray, seawater wetting and deicing salts [2].
The methodologies of this study is by using a steel concrete cube and divide one
surface of the concrete into several important points such as point A until point E.
The scope of this experiment is by observing the corrosion effects over time.
Figure 2 - Percentage steel mass loss increase with time [2]
From figure 2, we observe that corrosion caused loss of mass towards the steel
rebar and behave differently from one point to another. Point D is the critical point
as it starts to corrode faster than other point and contribute to higher mass losses.
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DATE : 15 DECEMBER 2013
Figure 3 - Pit depth evolution with time [2]
Due to the result in figure 2, the pit depth as transmitted in figure 3 provides with
the results that shows the relativity between losses of mass and the pit depth. All
these points are connected together thus affects the corrosion current and
expedites steel loss and simultaneously increases the crack width. The pattern learn
from this study is when one point start to corrode, it will affect the other point thus
contributing to material failure.
Towards the end of this study, one of the possible ways to prevent the corrosion to
be taken place is by carefully studied on the effects of the water cement ratios to
eliminate the presence of pores in the concrete structure.
There are some studies that applied Finite Element Analysis (FEA) towards the
corrosion of steel rebar in their investigation of concrete cracking due to steel
corrosion. This study highlighted the principal effects of steel corrosion on
structures is due to the cracking of concrete caused by the volumetric expansion of
corroded steel bars [3]. A formation of rust detected through electrochemical
process initiated by the dissolution of iron ions from bar surface and transformation
of the dissolved metal into corrosion products [3]. Since the rusts occupy a larger
volume than their parent metal, a radial expansion of a corroding bar would take
place around its circumference, which causes a hoop tension and radial
compression strains within the surrounding concrete. As corrosion of a steel bar
continues both hoop tension and radial compression strains of concrete increase.
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6. ASSESSMENT OF REINFORCING STEELS IN CONCRETE BY USING NDT (HALF-CELL POTENTIAL)
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DATE : 15 DECEMBER 2013
Once the maximum tensile strain of the concrete due to its hoop and radial strains
exceeds its deformation capacity, cracking, spalling and even delimitation of
concrete cover can occur. [3]
0.0007 mm for internal crack
0.0045 mm for External Cracking
0.0032 mm for Internal Penetration
0.0049 mm for External Cracking
Figure 4 - Mechanism of beam cracking and delamination due to corrosion [3]
Figure 4 shows that, as corrosion of the steel bars in terms of radial expansion
increased from 0.0007 mm to 0.0049 mm, the cracking of the concrete beam
throughout its section experienced four different types or stages: Internal Cracking,
Internal Penetration, External Cracking and External Cracking. Initially, no cracks
could be found for a small radial expansion. However, once the radial expansion
reached at 0.0007 mm, cracks first appeared on the internal surface of the concrete
cover and were distributed equally around and nearby each bar, which is defined as
Internal- Cracking. As the radial expansion increased to about 0.0032 mm, the
cracks already formed propagated through the concrete between two steel bars
and joined up with each other, which is referred to as Internal Penetration or
delamination. As the radial expansion further increased to 0.045 mm and 0.0049
mm, cracks eventually penetrated the 25 mm thick concrete cover and progressed
horizontally to beam side surface (HS) and vertically to beam bottom surfaces (VB),
which were referred to as External Cracking (HS) and External Cracking (VB),
respectively.
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1.2. Literature review
In general terms, the corrosion in steel rebar consists of 3 stages. The first stage or
the initiation stage is the depassivation cause by the diffusion of CO2 or chlorides to
the steel. The second stage or activation stage witness the rebar network to start to
corrode and the formation of rust start to appear visibly. The third stage is the
deterioration as cracking and spalling occur [1].
Since the corrosion is the main elements that threaten the building structures, early
monitoring is necessary before the visible and critical deterioration developed. 2
non-destructive techniques are commercially available in order to investigate this
issue; half-cell potential and polarization resistance [4]. The common selection is the
half-cell potential measurement due to its simplicity and effectiveness in
determined the presence of corrosion. Using half-cell the corrosion potential is
measured not near rebar but on the concrete surface.
The half cell potential measurement is an electrochemical technique commonly
used by engineers to assess the severity of corrosion in reinforced concrete
structures [5]. The normal conceptual of this measurement is using copper/copper
sulphate (Cu/CuSO4) standard reference electrode placed on the surface of the
concrete with the steel reinforcement underneath.
Figure 2 – Schematic diagram of half cell potential measurement technique [5]
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DATE : 15 DECEMBER 2013
From figure 2, the reference electrode is connected to the negative end of the
voltmeter and the steel reinforcement to the positive. This method is found to be a
success for the case of bridge deck corrosion surveys thus formed the basis of the
ASTM standard of C876 that provides general guidelines for evaluating corrosion in
concrete structures [5].
2 WORK COMPLETED
This experiment requires strong relationship between multiple parties. Several work
completed at this stage involves communication. Among the completed task so far are:
I.
II.
III.
IV.
V.
VI.
VII.
Obtaining Nuclear Agencies of Malaysia concrete grade measurement; G10, G15,
G20, G25, G30, G35, G40 and G45 from Mr. Azreen
Discussing with Mr. Azreen about the detailed methodology on the experiment as
per industrial standard
Methodologies proposed with Mr Azreen are being discussed with FYP lecturer
Dr. Abdul Aziz. His comments widen the scope of the study into 4 type of water;
sea water, salt marsh water, river water and normal water (in order to execute
the corrosion process) and the concrete grade investigation to be conducted only
for G10, G20, G30 and G40.
Request assistant from material lecturer Mr. Zainuddin Yahya for the investigation
of material corrosion rate
Early communication has been made with the technician who responsible in
keeping the EuroCell™ Electrochemical Cell Kit, Gamry Instrument for corrosion
rate investigation
Obtaining Letter of Introduction from COE Dean as verification on the
collaboration between Uniten and Nuclear Agencies of Malaysia as requested by
Dr. Syukri Mohd the industrial supervisor
The graph of result has been draft in order to record all the readings for this
experiment (yet to be comments)
3 PROBLEMS
During the execution of this stage, there are 2 main problems. The first problem is
Gamry instrumentation from Uniten lab. Proper procedure about executing this
experiment is yet to be discovered through discussion with Mr. Zainuddin. There are
uncertainties in using this equipment due to the fact that this instrument only was being
used for FYP project only.
The second problem is finding a source of water type. The four type of water that being
specified earlier is available in Malaysia, however obtaining all of them can be time and
money consuming. Further discussion about this is yet to be conducted.
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9. ASSESSMENT OF REINFORCING STEELS IN CONCRETE BY USING NDT (HALF-CELL POTENTIAL)
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DATE : 15 DECEMBER 2013
4 METHODOLOGY
Executing this study requires multiple sample of concrete embedded with steel rebar.
The study will cover up multiple grade of concrete; G10, G15, G20, G25, G30, G35, G40
and G45 and observe the effect of corrosion of steel rebar towards this grade. A
difference between grades is the mixture of cement, water, fine aggregate and course
aggregate content.
The scope of this study covers multiple environment, thus several water sample need to
be search in order to fulfil the study requirements. There are 4 sample of water that
need to be search for; sea water, salt marsh water, river water and normal water.
The study is split into 2 type of experiment. One experiment is to study the corrosion
rate of the steel rebar and another experiment is to observe the severity of corrosion in
concrete.
4.1. Procedure for experiment 1 (Corrosion rate investigation)
I.
Search for 4 water sample in different places:
Sea water
Figure 3 – Tentative place for Sea water, Port Dickson (Sources
Google Maps)
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10. ASSESSMENT OF REINFORCING STEELS IN CONCRETE BY USING NDT (HALF-CELL POTENTIAL)
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DATE : 15 DECEMBER 2013
River water
Figure 4 – Tentative place for river water, Sungai Chilling (Sources
Google Maps)
Salt marsh water
Figure 5 – Tentative place for salt marsh water, Bagan Lalang
(Sources Google Maps)
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Normal water
For normal water, the study will use the normal tap water that being
used in Malaysian daily life
II.
III.
IV.
V.
VI.
VII.
Put each water in pail of close basin
Obtaining pieces of steel rebar from Nuclear Agency of Malaysia; total
number of 48 specimen
Put 12 specimen in each pail of basin
Set up the Gamry EuroCell™ kit and observe the corrosion process for 3 days
to predict the corrosion pattern to each specimen
If the corrosion process is at lower rate, it is best to check the rate weekly
depends on the situation
Obtaining the percentage corrosion to be 0, 20, 40, 60, 80 and 100 for each
water type
4.2. Procedure for experiment 2 (Severity of corrosion in concrete)
I.
II.
III.
After obtaining the desired percentage for each specimen (the reading of
EuroCell™ indicate the corrosion to be at 0, 20, 40, 60, 80 and 100 at specific
steel rebar) the steel rebar is taken out from the basin and embedded into
concrete cube
The concrete mixture are blended according to grade G10, G20, G30 and
G40 and the ratio between cement, fine aggregate (sand), coarse aggregate
(broken stone) and water are highlighted in Attachment 2
The dimension for the cube and the embedded rebar steel are as per below:
150 mm
TOP VIEW
50 mm
ISOMETRIC VIEW
150 mm
75 mm
150 mm
IV.
V.
VI.
The concrete are left to dry for about 1 or 2 days
The cube will be divided into a few identified points and the half cell
measurement of corrosion will be taken from the points identified.
All results were recorded into the table as per Attachment 3
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12. ASSESSMENT OF REINFORCING STEELS IN CONCRETE BY USING NDT (HALF-CELL POTENTIAL)
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DATE : 15 DECEMBER 2013
5 APPARATUS
There will be 2 equipments that will be used in order to conduct this study.
I.
Half cell potential equipment
Half cell or can be called reference electrode circuitry (Figure 3) as a whole
instrument consists of several parts:
Figure 3 – Reference Electrode Circuitry [6]
a)
b)
c)
d)
II.
Reference Electrode (Cu/CuSO4)
Reinforcing steel rebar
Concrete mixture
Digital voltmeter
Gamry and Princenton Computerized Corrosion Measurement Systems
Gamry software is used as a corrosion measurement in order to determine the
percentage of corrosion that occurs in particular steel. Figure 4 shows that the
proper physical set up that need to be done in order to conduct the testing using
this software. All the data linked to software and percentage of corrosion is
transmitted through computer.
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DATE : 15 DECEMBER 2013
Figure 4 – Gamry corrosion instruments, EuroCell™ [7]
The basis of Gamry corrosion testing is by using Tafel graph. Tafel analysis is
performed by extrapolating the linear portions of a log current versus potential
plot back to their intersection.
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DATE : 15 DECEMBER 2013
Figure 5 – Basic Tafel graph [7]
Figure 5 explain that the vertical axis is potential and the horizontal axis is the
logarithm of absolute current. The theoretical current for the anodic and
cathodic reactions are shown as straight lines. The curved line is the total
current - the sum of the anodic and cathodic currents [7]. This is the current that
you measure when you sweep the potential of the metal with your potentiostat.
The sharp point in the curve is actually the point where the current changes signs
as the reaction changes from anodic to cathodic, or vice versa [7]. The sharp
point is due to the use of a logarithmic axis. The use of a log axis is necessary
because of the wide range of current values that must be displayed during a
corrosion experiment [7].
6 WORK SCHEDULE
The change of schedule due to certain circumstances as highlighted in section 2 of this
paper are transmitted in attachment section. Other work schedule will be conducted the
same with the schedule timing subjected to unavoidable reason.
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MPRB 412 - PROGRESS REPORT 2
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DATE : 15 DECEMBER 2013
7 REFERENCES
I.
Books and Technical Journal
[1] John P. Broomfield, “Corrosion of steel in concrete – Understanding,
investigation and repair,” E&FN Spon, 1997.
[2] K.G. Papakonstantinou, M. Shinozuka, “Probabilistic model for steel corrosion
in reinforced concrete structures of large dimensions considering crack effects,”
Department of Civil and Environmental Engineering, University of California
Irvine, Irvine, USA, 19 June 2013.
[3] Y.G. Du, A.H.C. Chan, L.A. Clark, X.T. Wang, F. Gurkalo, S. Bartos, “Finite
element analysis of cracking and delamination of concrete beam due to steel
corrosion,” Department of Engineering and Built Environment, Anglia Ruskin
University, Chelmsford CM1 1SQ, United Kingdom, 8 April 2013.
[4] Veerachai Leelalerkiet, Je-Woon Kyung, Masayasu Ohtsu, Masaru Yokota,
“Analysis of half-cell potential measurement for corrosion of reinforced
concrete,” Shigoku Research Institute, Takamatsu, Japan, 12 October 2003.
[5] Ping Gu, JJ Beaudoin, “Obtaining Effective Half Cell Potential Measurements
in Reinforced Concrete Structures”, National Reasearch Council of Canada, July
1998.
[6] “Standard Test Method for Corrosion Potentials of Uncoated Reinforcing Steel
in Concrete,” American Society for Testing and Materials (ASTM), C876-09, 2012.
[7]
“EuroCell™
Electrochemical
Cell
Kit”,
Gamry
Instruments,
http://www.gamry.com/products/cells/eurocell-corrosion-cell/
II.
People
a.
b.
c.
d.
Dr. Abdul Aziz (FYP Supervisor)
Mr. Zainuddin Yahya (Material Lecturer)
Dr. Syukri Mohd (Industrial Supervisor)
Mr. Noor Azreen (Industrial Supervisor)
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17. Gantt Chart for Final Year Project 1
FINAL YEAR PROJECT 1
October
Month
Item Week
Project title selection
Research and findings
FYP proposal
Literature review
Progress report 1
Experimental setup
Progress report 2
Report compilation
Slide preparation
Oral Presentation
Logbook write up
1
2
3
November
4
1
2
3
December
4
1
2
3
January
4
1
2
3
4
18. Gantt Chart for Final Year Project 2
** All experiment are planned to be conducted during short semester
Month
Item Week
Result analysis
Redo testing
Finalize analysis
Progress report 3
Comparison of data
Discussion
Slide preparation
Oral Presentation
Thesis compilation
Logbook write up
FINAL YEAR PROJECT 2
June
1
2
3
4
July
1
2
August
3
4
1
2
3
September
4
1
2
3
4
