Corrosion Behaviour Of Steel For Simulated Concete In Choride Aqueous Solution.

UTeM Library (Pind.112007)

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mengaku membenarkan tesis (PSMISarjanalDoktor Falsafah) ini disimpan di
Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat
kegunaan seperti berikut:
1. Tesis adalah hak milik Universiti Teknikal Malaysia Melaka .
2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan
untuk tujuan pengajian sahaja.
3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran
antara institusi pengajian tinggi.
4. **Sila tandakan (d)

(Mengandungi maklumat yang berdarjah keselamatan
atau kepentingan Malaysia yang termaktub di dalam
AKTA RAHSIA RASMl 1972)

SULlT

(Mengandungi maklumat TERHAD yang telah ditentukan
oleh organisasilbadan di mana penyelidikan dijalankan)

TERHAD
TlDAK TERHAD

Disahkan oleh:

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(TANDATANGAN PENULIS)
MOHD. ASYADI ' A U M BIW MOHB. ABI,

Alamat Tetap:
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Fakub K,ruteraan
PensyarahPermuah"

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Maliiysla Melaka
Karung Berkunc~1200 Ayer Keroh
75450 h l a k a

Tarikh: 23 ' 4 .J

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Tesis dimaksudkan sebagai tesis bagi ljazah Doktor Falsafah dan Sarjana secara penyelidikan, atau
disertasi bagi pengajian secara kerja kursus dan penyelidikan, atau Laporan Projek Sarjana Muda (PSM).I
** Jika tesis ini SULlT atau TERHAD, sila lampirkan surat daripada pihak berkuasalorganisasi berkenaan
1
densan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebaqai SULlT atau TERHAD.

DECLARATION

I hereby, declare this thesis entitled "Corrosion Behaviour of

Steel for Simulated Concrete in Chloride Aqueous Solution"
is the result of my own research
except as cited in the references.

Signature
Author's Name
Date

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....................................................
C0 u u
(- k\litd?
:.....................................................
2 o - k-20
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.......................................................

APPROVAL

This PSM submitted to the senate of UTeM and has been as partial fulfillment of the
requirements for the degree of Bachelor of Manufacturing Engineering (Materials
Engineering). The members of the supervisory committee are as follow:

(Main Supervisor: Mohd. Asyadi 'Azam bin Mohd. Abid)
(Official Stamp & Date)
MOHD. ASYADI ' A U M BIN MmHD. M I D

Pensyarah
Fakulti Keiurutenan Pernbuatan
Univers~tiTennikai Malaysia Metaka
Karuna Berkunc~1200, Ayer Keroh

Co-Supervisor
(Oficial Stamp & Date)
MOHAMAD HAlDlR BIN MASLAN
Tutor
Fakulti Kejun~teraanPembuatan
Universili Tekntkal Malaysia Melaka
Karung Berkunci 1200, Ayer Keroh
75450 .Fvlelilka

ABSTRACT

Steel reinforced concrete is probably the most extensively used construction
material in the world. However, many cases of structural failure have occurred during
recent years especially for those structures that are exposed to marine environment
such as harbour structures and bridge structures. Structural failures are mainly due to

the steel reinforcement corrosion. The objective of this study has been conducted to
look into the effect of different concentration of chloride content on corrosion rate in
steel reinforced concrete. The second objective is to compare and study the
morphology of reinforced steel before and after corrosion based on difference
concentration of chloride in concrete. The reinforced steel bar used in this study was
based on commercially available which obtained from Ann Joo Steel Berhad. Four
steel reinforced concrete specimens were manufactured with cement/sand/water ratio
of 1:3:0.5 by weight. Then, each of the specimens was subjected to concentrations of
sodium chloride solution with the percentage of 1%,3%, 5%, and 7% by weight for
reveal the relationship between chloride ion and corrosion rate. The morphology of
reinforced steels is compared and analysis. The study is shown that the corrosion rate
of reinforced steel bar is directly proportional to the chloride concentration. The
corrosion products on reinforced steel bar also increase with the chloride
concentration .Some pits are found on the reinforced steel .Finally, the potential of
cost saving and life saving is high via understanding the corrosion behaviour and
problem of steel reinforced concrete before tragedy occurred.

ABSTRAK

Konkrit jenis besi tetulang merupakan bahan binaan yang paling banyak

digunakan dalam dunia. Akan tetapi, terdapat banyak kes kegagalan stmktur berlaku
kebelakangan ini temtama pada struktur dibina di persekitaran laut seperti struktur di
labuan dan jambatan. Kegagalan struktur ini adalah disebabkan pengaratan besi
tetulang dalam konkrit. Objektif bagi kajian ini adalah menentukan kesan perbezaan
kepekatan klorin ke atas kadar pengaratan pada konkrit jenis tetulang. Objektif kedua
adalah mempelajari and membanding microstruktur untuk tetulang besi sebelum dan
selepas pengaratan pada kepekatan berlainan dalam konkrit. Besi tetulang yang
digunakan adalah diperolehi dari Ann Joo Steel Berhad. Empat konkrit besi tetulang
disediakan pada nisbah simen/pasir/air 1:3:0.5 mengikut berat. Kemudian, empat
sample ini direndamkan dalam cecair natrium klorin.dalam peratusan I%, 3%, 5%
dan 7% mengikut berat supaya hubungan di antara pengaratan dan kepekatan ion
kloride dapat dikaji. Microstruktur untuk besi tetulang adalah dibanding dan
dianalisis.keputusan kajian ini menunjukkan kadar pengaratan tetulang. besi adalah
berkadar langsung dengan kepekatan ion kloride. Bahan pengaratan pada tetulang
besi juga bertambah dengan kepekatan ion kloride yang lebih tinggi. Lubang-lubang
dapat deperhatikan pada tetulang besi. Akhirnya,

berpotensi tinggi untuk

menjirnatkan jumlah wang dan nyawa jika masalah dan amalan pengaratan diketahui

sebelum tragedi berlaku.

DEDICATION

ADKNOWLEDGEMENT

First, I would like to express my sincere and appreciation to my
supervisors,Mohd Asyadi Azam Bin Mohd Abid who always have been providing
guidelines and related information for the completion of the thesis. He has shown
great faith in me and has been very supportive throughout the research. In addition,
not forgetting to extend my gratitude to University Tun Hussein OM (UTHM) and
their technicians where I carried on my research. To staffs of Ann Joo Steel Berhad
who is willing to send me some raw material for the research. Furthermore, I would
like to express my appreciation to technicians in polymer lab and material lab who
willing to share their knowledge to me during the research. Also, not forgetting to
express my sincere to all lecturers of Manufacturing Engineering Faculty
(FKP),UTeM for their nurturing.

Finally, to my family and friend for their care and encouragement that has
inspired me to complete this research. This research could not have been completed

without their unconditional support. I would like to end by saying that people
mentioned above will forever hold dear in my heart and will never be forgotten.
Thank you all.

TABLE OF CONTENTS
Abstract ...........................................................................................i

..

Abstrak .......................................................................................... .ii

...

Dedication .......................................................................................ill
Acknowledgment .............................................................................. .iv
Table of Contents ................................................................................v
List of Figures ...................................................................................ix
List of Tables ....................................................................................xi

..

List of Abbrebiations, Symbols, Specialized Nonmenclature ...........................xi1

1. INTRODUCTION
1.I Background ...............................................................................1
1.2 Problem Statements ..................................................................... .2
1.3 Objectives .................................................................................3
1.4 Scope of Study ............................................................................3

2. LITERATURES REVIEW

2.1 Electrochemical Theory of Corrosion ..................................................5
2.2 Type of Concrete ..........................................................................6
2.2.1

Cement ..............................................................................8

2.2.2

Water ................................................................................9

2.2.3

Aggregates .........................................................................9

2.2.4

Admixtures ........................................................................10

2.3 Type of Steels ............................................................................I0
2.3.1

Carbon Steels or Unalloyed Steels .............................................11

2.3.1.1 Low Carbon Steels ............................................................ 11
2.3.1.2 Medium Carbon Steels ...................................................... ..I1

2.3.1.3 High Carbon Steels ............................................................ 12
2.3.1.4 Ultra Carbon Steels ............................................................ 12
2.4 Mechanisms and Principal of Reinforcement Corrosion in Concrete ............12
2.4.1

General Aspects .................................................................. 12

2.4.1.1 Stages in the Deterioration Process ..........................................14

(a) Initiation Stage .....................................................................15
@) Propagation Stage .................................................................16
2.4.2 Chloride Induced Corrosion ....................................................17
2.4.2.1Pitting Corrosion ...............................................................18
2.4.2.2Chloride Induced Corrosion Initiation .......................................20
2.4.2.3 Chloride Threshold Level (CTL).............................................22
2.4.2.4Penetration of Chloride ........................................................23
2.4.3

ElectrochemicalAspects ........................................................27

2.4.3.1 Electrochemical Mechanism of Corrosion .................................27
2.4.3.2Concrete Containing Chlorides ..............................................30

(a) Corrosion Initiation and Pitting Potential ......................................30
@) Propagation ........................................................................31

2.4.4

Corrosion Behaviour of Steel Reinforced Concrete-Corrosion Rate .....32

2.4.4.1Factors Mecting of Corrosion Rate .........................................33

(a) Concrete Cover Thickness .......................................................33
@) Aggressiveness Condition .......................................................35

(c) Cracks ..............................................................................36
2.4.4.2Corrosion Rate Measurement-Tafel Plot Technique .......................37
2.4.4.3Corrosion Rate Measurement-Linear Polarization Resistance (LPR) ...38
2.4.5

Corrosion Behaviour of Steel Reinforced Concrete-Morphology .......40

2.5 Other Type of Reinforcement Corrosion .............................................41
2.5.1

General Corrosion ..............................................................41

2.5.2

Bacterial Corrosion ............................................................42

2.5.3

Concentration Cells ............................................................ 43

2.5.4

Differential-Oxygen Cells .....................................................
43

2.5.5

Dissimilar Metal Corrosion or Galvanic Cells .............................44

2.5.6

Stray Current ....................................................................44

.

3 METHODOLOGY ........................................................................45
3.1 Introduction ..............................................................................45
3.2 Process Sequence ........................................................................46
3.3 Steel Bar Preparation ...................................................................47
3.4 Formwork Frame ........................................................................49
3.5 Mix and Form Reinforced Concrete ..................................................53
3.6 Electrochemical Testing and Measurement ..........................................57
3.6.1

Electrolyte .........................................................................57

3.6.2

Electrodes ..........................................................................57

3.6.3

Testing Program ..................................................................59

3.7 Microstructure or Morphology Observation .........................................62

.

4 EXPERIMENTAL RESULTS AND DISCUSSIONS ..............................65
4.1 Anodic Polarization Curve ............................................................ -65
4.1.1

Sodium Chloride Aqueous (1%) .............................................. 65

4.1.2

Sodium Chloride Aqueous (3%) .............................................67

4.1.3

Sodium Chloride Aqueous (5%) .............................................69

4.1.4

Sodium Chloride Aqueous (7%) .............................................71

4.1.5

Comparison between 1%.3%. 5% and 7% wt NaCl .......................74

4.2 Corrosion Resistance ...................................................................77
4.3 Corrosion Rate ...........................................................................78
4.4 Microscopic ..............................................................................80
4.4.1

Scanning Electron Microcopy (SEM) .......................................80

vii

4.4.2

Optical Microscope (OM) ................................................... ..85

5. RECOMMENDATION AND CONCLUSION
5.1 Recommendation ........................................................................89
5.2 Conclusion ...............................................................................90

REFERENCES ................................................................................92

APPENDICES

A

Gantt Chart for PSM I

B

Gantt Chart for PSM I1

C

Tafel Plot for Specimen in 1% wt Sodium Chloride Solution

D

Tafel Plot for Specimen in 3%wt Sodium Chloride Solution

E

Tafel Plot for Specimen in 5%wt Sodium Chloride Solution

F

Tafel Plot for Specimen in 7% wt Sodium Chloride Solution

viii

LIST OF FIGURES

Cross Section of Steel Bar and Concrete
Portland Cement
Corrosion in Reinforced Concrete
Initiation and Propagation Periods for Corrosion in a Reinforced
Concrete
Pitting Corrosion of Steel in Concrete
Schematic Representation of the Process of Corrosion Initiation
Arising from Chloride Ions
Corrosion Initiation Evident from the Corrosion Product on the
Concrete Surface at the Location of a Void
Corrosion Mechanism for Concrete Containing Ion Chloride
The Corrosion Process for Steel in Concrete
Electrochemical Mechanism of Corrosion of Steel in Concrete
Example of the anodic polarization curve of steel in concrete with
different aggressive ions
Reduction of the Initiation Time of Corrosion due to Reduction in
Concrete Cover Thickness
Example of Bacteria Corrosion

The Whole Process Sequence in Project Corrosion Study
Low Carbon Steel Deformed Bars (MS 146:2000)
US Portable Cleaner (JEIOTECH LAB COMPANION)
Process Flow for Low Carbon Steel Deformed Bar Preparation
Concept for Formwork Frame Setting Process
Process Sequence for Setting Formwork Frame

Formwork Frame
Concept for Concrete Mixing Process
Process Sequence for Mix and Form Reinforced Concrete
Schematic for Reinforced Concrete
Reinforced Concrete Specimen
Reference Electrode
Counter Electrode
PGSTATlOO Potentiostat
Set up for Polarization Test and Corrosion Rate Measurement
Schematic Diagram of Test Setup for Corrosion Rate Measurement
Process Sequence for Electrochemical Test and Measurement
Optical Microscope (CARL ZE1SS:Axioskop 2 MAT,2003)
Scanning Electron Microscope (CARL ZEISS EVO 50)
Process sequence for Morphology Observation

Anodic Polarization Curve of Low Carbon Steel in Concrete in
Aqueous Solution with 1% wt Sodium Chloride
Anodic Polarization Curve of Low Carbon Steel in Concrete in
Aqueous Solution with 3% wt Sodium Chloride
Anodic Polarization Curve of Low Carbon Steel in Concrete in
Aqueous Solution with 5% wt Sodium Chloride
Anodic Polarization Curve of Low Carbon Steel in Concrete in
Aqueous Solution with 7%wt Sodium Chloride
Anodic Polarization Curve of Low Carbon Steel in Concrete
with Difference Weight Percentage (I%, 3%, 5 % &7%) of
Sodium Chloride Aqueous Solution
Morphology of the Rebar Surface Before Anodic Polarization Test

4.6b

Morphology (SEM) of the Rebar Surface after Anodic Polarization
Test in 1 %(i), 3%(ii), S%(iii) and 7%(iv) Sodium Chloride

4.7a

Microscopic of the rebar surface before anodic polarization
test under magnification 500X

4.7b

82

85

Morphology (OM) of the rebar surface after polarization
test in l%(i), 3%(ii), S%(iii) and 7%(iv) NaCl (Mag:500)

86

LIST OF TABLES

2.1

Minimum Values for Concrete Cover Depth, Simplified from
Eurocode 2 with Regard to Corrosion Protection of Steel for Structure
Class 4 and Exposure Classes defined by EN 206.These Values should
be increased by 10mm to obtain the Nominal Cover Depth.

34

3.1

Composition of Low Carbon Steel Deformed Bar (MS 146:2000)

48

4.1

Electrochemical data for rebar in concrete specimens placed in
sodium chloride aqueous solution at I%, 3%, 5% and 7% C1-

4.2

77

Corrosion rates obtain by extrapolation of Tafel plot after
17 minutes exposure

78

xii

LIST OFABBREBIATIONS, SYMBOLS, SPECIALIZED
NOMENCLATURE

%
f

A

A h 2

-Ampere per centimeter square

ASTM

- American Standard Testing Method

B

- Stern-Greary Constant.

ba

- Slope of the anodic Tafel reaction

bc

- Slope of the cathodic Tafel reaction

BS

-British Standards

BSI

-British Standards Institution

C

-Carbon

c1-

-Chloride Ion

CR

- Corrosion Rate

G
CTL

- Surface Chloride Content

cx

- Total Chloride Content (% by mass of cement or concrete)

D~PP

- Apparent Diffusion Coefficient for Chloride (m2/s)

%i&b

- Pitting Potentialbreakdown potential

Em,

-Corrosion potential

erfc

- Error Function

EW

- Equivalent Weight

Fe

-Ferrite

Fe(OH)2

-Ferum(II)Hydroxide

Fe(OH)3

- Ferum(II1)Hydroxide

- Chloride Threshold Level

~ e ~ + -Ferrite (11) Ion
~ e ~ '

-Ferrite (111) Ion

Fe304

-Ferum(iV)Oxide(III)

g

-Gram

IT

-Hydrogen Ion

H20

-Water

HCl

-Hydrochloric Acid

1 mr

-Rate of the overall process of corrosion

1,

- Anodic current

Ic

-Cathodic Current

Icon

-Current that circulates inside the concrete from the anodic area to
the cathodic area

- Corrosion Current Density
- Intensity of the corrosion current
-Current that flow inside the steel from the cathodic area to the
anodic
Kg

-Kilogram

1

-Little

LPR

- Linear Polarization Resistance

m3

-Meter Cubic

mA/m2

-Miliampere per meter square

ml

-Mililiter

mm

-Millimeter

mdy

-Millimeter per year

MPa

-Mega Pascal

am"

-Megapascal Root Meter Square

MS

- Malaysia Standard

Nat

-Sodium Ion

xiv

NaCl

- Sodium Chloride

0 2

-Oxygen

OH-

-Hydroxide Ion

OM

-Optical Microscope

PSM I

- Project Sarjana Muda I

PSM I1

- Project Sarjana Muda I1

R.H

-Relative Atmospheric Humidity

RP

- Polarization Resistance

S

-Second

SCE

-Saturated Calomel Electrode

SEM

- Scanning Electron Microscope

t

-Time

TP

- Tafel Plot Technique

us

-United State

USA

-United State American

v

-Volt

wlc

-Water over Cement

XRD

- X-ray Diffraction

pVcm2

-Micrometer per centimeter square
-Micrometer

- Density

CHAPTER 1
INTRODUCTION

1.

Background
Corrosion problem occurred on earth for more than a century. It occupied

many fields that have application of metal such as electronic sector, agricultural
sector, manufacturing sector and chemical plant. However, corrosion happen in
construction field is the most critically because it involves large amount of human
that live under these structures.
Corrosion of reinforcing steel in concrete is the most deterioration process
influence steel reinforced concrete structures or construction field. Steel reinforced
concrete structures form an important part of our infrastructure. Buildings, slabs,
beam, bridge decks and piles, all these structures can be executioned with steel
reinforced concrete. Concrete can provides physical and chemical protection to the
reinforcing steel. The main aim of physical protection is hindered the ingress of
aggressive species such as oxygen, moisture and chloride ion to the steel concrete
interface. The chemical protection is involved via high basicity of pore solution such
as sodium, calcium and potassium oxides. Concrete provides the ideal environment
for protecting embedded steel because of its alkalinity. A layer of passive protection
film is formed on the reinforcing steel surface under high alkalinity. Therefore, the
reinforcing steel is not subject to corrosion and possesses almost unlimited durability.

However, the presence of chloride ions introduced into concrete from
contaminated aggregates or water and external environment in excess of a critical
threshold level can damaged the passive protection film. After that, the durability of
reinforced concrete structures may be drastically limited. This chloride induce
corrosion of reinforced concrete structure may often mention on marine structure,
both on shore and off shore. It becomes the major cause of the infrastructure
deterioration in many parts of the world.

When the corrosion is initiated in reinforced concrete structures, the
structures need to be repaired, renewed or replaced within a short period of years.
This is extremely expensive, as can be noticed that the remediation of concrete
bridges in the USA undertaken as a direct result of corrosion of the reinforcing steel
cost the US state departments 5 billion in the year 2000; all forms of corrosion
damage to concrete in UK in 1997 was f750million (BCA,2000).

1.2

Problem Statements
Concrete essentially take care of compressive stresses but weak in tension.

Therefore, steel should embed in concrete to strength its tensile property. The
concrete that after embed steel is called as reinforced concrete.

Usually the interaction between the material of the structure and the
environment is called corrosion. Studying the history of steel reinforced concrete that
very rare cases where a structure failed due to mechanical loadings which have not
been considered at the design stage. The problem, instead, arises due to lack of
sensitivity and knowledge of engineers when dealing with questions of corrosion.
One of the main source of corrosion in reinforce concrete is caused by chloride. The

high numbers of structures where corrosion and especially steel reinforcement
corrosion has led to premature failures and costly restoration. As the saying state that
"prevention is better than cure", it is necessary to understand, study, and prevent the
corrosion problem before it occurred.

Corrosion of steel reinforcement in structures is now a feature which
figures heavily in the maintenance of existing buildings, contributed to a number of
structural collapses and involved large amount of human life. Concrete condition is
simulated to investigate the influence of aggressive element such as ion chloride in
corrosion of steel in concrete.

1.3

Objectives
The purposes of this project are:

i)

To study the effect of different level of chloride content on corrosion rate in
steel reinforced concrete.

ii)

To compare and study the morphology reinforced steel before and after
corrosion based on difference concentration of chloride in concrete.

1.4

Scope of Studies
Basically, the objective of this project is to study the influence of chloride

which led to premature failures of construction. The research work will focus on
study on the behaviour and microstructure of corroded steel in the laboratory scale.
Among the methods that will be carried out to determine current trend of corrosion in
Malaysia's buildings are included internet research, reference of previous and

interview expert in this topic. It will involve several processing stage in corroding
and checking the corrosion rate of samples by using electrochemical technique. This
will followed by the observation stage in order to investigate microstructure and
other. The finding will be analysis and the method of prevention corrosion in
reinforce concrete will be suggested.

CHAPTER 2
LITERATURE REVIEW

2.1

Electrochemical Theory of Corrosion
Corrosion can be defined in different ways but the common interpretation of

the term is deterioration of a material especially metal by reaction with species in the
environment to form chemical compound. The' concept of corrosion can involved
wider sense, where attack on non metallic materials. Corrosion of metallic material
can be separated into three main groups. The first group is corrosion in other fluid
like molten metal and fused salt. The second group is called wet corrosion, where the
corrosive environment is water with dissolved species. The liquid is known as
electrolyte and it is an electrochemical process at room temperature. The last group
of corrosion is involved dry gas corrosive environment. Therefore, this group is
known as dry corrosion. This group of corrosion is also often called chemical
corrosion or high temperature corrosion.

This project concentrates just on wet corrosion. This corrosion process
consists of an anodic reaction and a cathodic reaction. In the anodic reaction
(oxidation), the metal dissolved at one site to form as positive ion

he location

where anodic reaction is called anode. The residual electrons released by the anodic
reaction are conducted via the metal to the cathodic area or cathode where they are
consumed in the cathodic reaction (reduction). It is seen that the process causes an

electrical circuit without any accumulation of charges. Electrode is an electronic
conductor which cathodic reaction and anodic reaction happens. Normally, the metal
works as electronic conductor. Between the anode and cathode, ionic and must flow
to avoid the build up of charge. Therefore, electrolyte is necessary for corrosion
process. The electrolyte is usually an aqueous solution of ions such as Na', Cl-, OHand ~ e ~The
+ . positive ions are called cations and the negative ions are known as
anions. If there is no external source of electrons is applied, the consumption of
electron in cathode must same rate to the generation of electron in anode. Based on
the condition, this dissolution process is called wet corrosion and the mechanism is
electrochemical. This electrochemical is occurred in steel reinforced concrete which
regarding to this project.

2.2

Q p e of Concrete
Concrete (Figure 2.1) is a multiphase material construction material

containing cement paste (unhydrated and hydrated compounds), water, aggregates
(sand and gravel) and sometimes admixtures in required proportions. Concrete
solidifies and hardens after mixing and placement due to a chemical process known
as hydration. The overall mechanical and physical properties of concrete depend on
the volume fraction and properties of the constituents and the mechanisms of
interaction between the separate phases.

Strength grading of concrete is prevalent in many countries. It is useful to
separate concrete into three general types based on compressive strength. These
include low strength concrete(1ess than 20MPa), moderate strength concrete (20 to
40MPa) and high strength concrete (more than 40MPa) (Pedeferri et al., 2000). In
Malaysia, the most common used concrete in structural work is moderate strength