Assessment and Repair of Chloride Induced Corrosion of Steel in Reinforced Concrete

7/29/2019 Assessment and Repair of Chloride Induced Corrosion of Steel in Reinforced Concrete

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INDIVIDUAL ASSIGNMENT B

CONCRETE DURABILTY

Assessment and Repair of Chloride Induced

Corrosion of Steel in Reinforced Concrete

KN Volmink

Word CountMain text 3455

Tables (5 x 150) 750Figures (2 x 150) 300

Total 4505


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INDIVIDUAL ASSIGNMENT BCONCRETE DURABILITYAssessment of Chloride Induced Corrosion of Steel in Reinforced Concrete

Individual Assignment BA reinforced concrete structure is to be surveyed for the corrosion of the steel due to chlorideattack. Describe and critically evaluate the test methods that can be used for theassessment of

a) the presence of corrosionb) the rate of corrosionc) the total amount of corrosion

By reference to a case study describe the renovation and rehabilitation of a structure thathas been found to suffer from extensive chloride-induced reinforcement corrosion.

Overall maximum length 4,500 words (excluding report title page, contents, reference listand appendices) with each diagram, figure etc. within the main text to count as 150 words.Number of words or word equivalents should be declared on the title page.Key diagrams, figures etc. should not be relegated to appendices.

In submitting your assignment report you are declaring that all the content is entirely yourown work except where indicated (by appropriate citation) that it is the work of others.


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ABSTRACT

Steel reinforced concrete structures exposed to chlorides are prone to corrosion due to the

resultant electrochemical activity. This corrosion reduces the structures service life and, if

not remedied, may lead to structural failure. The encasement of steel reinforcing in concreteinherently provides protection against corrosion however exposure to chlorides associated

with corrosive conditions eliminate this protection and induces corrosion. The exposure of

concrete to chlorides may be as a result of chloride containing constituent materials or by

diffusion from external chloride sources such as de-icing and marine salts. The ability to

successfully prevent or remedy chloride induced corrosion relies on the successful

assessment of the presence of corrosion, the rate of corrosion and the extent of corrosion

based on an understanding of the corrosion mechanism. With this knowledge gained about

corrosion, preventative measures can be implemented and structures which have already

been effected can successfully be repaired and rehabilitated.


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TABLE OF CONTENTS

Page

1. INTRODUCTION ........................................................................................... 11.1 Corrosion Process ................................................................................................... 11.2 Chloride Penetration ................................................................................................ 21.3 Macrocell Corrosion ................................................................................................ 22. CORROSION ASSESSMENT ....................................................................... 42.1 Introduction ............................................................................................................. 42.2 Presence of Corrosion ............................................................................................. 4

2.2.1 Visual Inspection........................................................................................ 42.2.2 Half-cell Potential ....................................................................................... 5

2.3 Corrosion Rate ........................................................................................................ 62.3.1 Concrete Resistivity ................................................................................... 6

2.4 Extent of Corrosion .................................................................................................. 82.4.1 Linear Polarisation ..................................................................................... 8

3. CASE STUDY: REHABILIATION BY USING IMPRESSED-CURRENTCATHODIC PROTECTION ........................................................................... 9

3.1 Introduction ............................................................................................................. 93.2 Cathodic Protection ................................................................................................. 9

3.2.1 Sacrificial Anode Cathodic Protection ........................................................ 93.2.2 Impressed-current Cathodic Protection ...................................................... 9

3.3

Components of an Impressed-current Cathodic Protection System ....................... 10

3.3.1 Preparation and Electrical Continuity ....................................................... 103.3.2 Anode Installation .................................................................................... 103.3.3 Power Connection ................................................................................... 10

3.4 Challenges of Impressed-current Cathodic Protection ........................................... 113.5 Conclusion ............................................................................................................ 114. REFERENCES ............................................................................................ 12APPENDIX A ........................................................................................................... 13


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LIST OF FIGURES

Figure 2-1 Corrosion of steel in aerated water (Domone, 2010) ............................................ 1Figure 2-2 Corrosion initiation from Chloride attack (Glass, 2003) ........................................ 2Figure 2-3 Macrocell corrosion inside concrete (Berke, 2006) ............................................... 3Figure 3-1 Cracking and spalling of cover concrete ............................................................... 4Figure 3-2 Wenner technique for measuring resistivity (Gowers and Millard, 1999) .............. 6LIST OF TABLES

Table 3-1 Half-cell potential (voltage in mV) vs. probability of corrosion (ASTM 876, 2009) .. 5Table 3-2 Factors causing errors in resistivity measurements (Gowers and MIllard, 1999) ... 7


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1. INTRODUCTION

1.1 Corrosion Process

Metals, such as steel used for reinforcing concrete, are naturally prone to corrosion.

This is because corroded (oxidised) steel is at a lower energy level than in itsmetallic state. However when in contact with an alkaline solution, such as in

concrete, reactions at the steel concrete interface form hydrated oxides which

create a passive film to the steel stopping any further corrosion. (Glass, 2003)

Disruption to this passive film by chloride ions is the initiation process (Berke, 2006)

of chloride induced corrosion.

The corrosion of the steel is further driven by an electrochemical process in which a

corrosion cell is produced. Positive steel (iron) ions are dissolved at the anode and

gives up electrons which are transported, through the steel, to the cathode where

the electrons are consumed in the formation of negative hydroxyl ions. This processis illustrated in Figure 1-1. (Domone, 2010)

The ions produced in the anodic and cathodic reactions then become Ferrous

hydroxide and then, through the consumption of oxygen, Ferric oxide (rust). The

volume of Ferric oxide is twice that of steel and when hydrated swells even further.(Broomfield, 1997) The increase in volume of these corrosion products result in

tensile stresses in the concrete which lead to cracking, particularly over the

reinforcement.

The corrosion process, from before any corrosion activity, to the disruption of the

passive film (depassivation) and finally to the cracking of the concrete is best

described as the service life of a structure. (Domone, 2010) This service life model

is further illustrated in Figure A-1 in Appendix A.

Assessment of where in the corrosion process a structure is would therefore

provide invaluable information into determining the remaining service life of a

structure.

Figure 1-1 Corrosion of steel in aerated water (Domone, 2010)


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1.2 Chloride Penetration

As stated previously it is the disruption of the passive film (which is stable in an

alkaline environment) around the steel reinforcing by chloride ions that induces

corrosion. The presence of these chloride ions can be as a result of chloride

contaminated materials and from de-icing salts and sea spray which penetrate the

concrete through diffusion as a result of a concentration gradient. (Glass, et al.,

2000)

Chloride ions attack the passive layer around the steel forming pits. This pit

formation coupled with a reduction in alkalinity, due to the hydrolysis of iron ions,

initiates corrosion and further produces hydrochloric acid. (Glass, 2003) This

initiation process is illustrated in Figure 1-2. (Glass, 2003)

The chloride ions are not consumed in the depassivation process but further allow

faster corrosion. The chlorides are recycled and difficult to remove making chloride

attack hard to remedy. (Broomfield, 1997)

Corrosion initiation however only occurs at a certain Chloride threshold level.

Values for this level cited by Glass (2003) range between 0.2 per cent and 2.5 per

cent (expressed as the ratio of Chloride to cement). The in-situ Chloride content of

a concrete structure can therefore be measured and used as an indicator of

corrosion potential, the more chlorides the greater the corrosion potential.

1.3 Macrocell Corrosion

Microcell corrosion occurs when the anodic and cathodic reactions are very closely

spaced which results in general, widespread corrosion. Chloride induced corrosionis however local with relatively small portions of corrosion, separated by large rust

free sections. This is indicative of a separation between the anodic and cathodic

reactions forming well defined macrocells.

The macrocell corrosion process is illustrated in Figure 1-3 with the top and bottom

layers of steel reinforcement in a slab forming the anode and the cathode

respectively. For the macrocell to be sustained a closed circuit of electrons flowing

from the anode to the cathode through a conductor, in this case other transverse

steel reinforcement and ions from the cathode to the anode, through the concrete

pore solution (electrolyte) must be maintained.

Figure 1-2 Corrosion initiation from Chloride attack (Glass, 2003)


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Broomfield (1997) states the following as contribtuting factors to macrocell

formation:

Chloride attack results in pit formation with small anodes being fed by large

cathodes.

The high levels of moisture associated with Chloride attack provides easy

transfer of ions through the concrete allowing separation between anodes

and cathodes.

The resistivity of the concrete determines the ease of transportation of ions between

the anode and the cathode thus also impacting on the rate of corrosion once a

corrosion cell (macrocell) has formed. (Gowers & Millard, 1999) If the resistivity of

concrete and the associated electrical current flow can be measured it can be used

to determine the corrosion rate which will be discussed later.

The disruption of the macrocell can also be used in the rehabilitation of structures

affected by chloride induced corrosion which will be discussed in the section on

Rehabilitation by using Impressed-current Cathodic Protection.

Figure 1-3 Macrocell corrosion inside concrete (Berke, 2006)


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2. CORROSION ASSESSMENT

2.1 Introduction

There are various methods for assessing chloride induced corrosion. These

methods range from basic physical methods such as visual inspection, chloridecontent and gravimetric weight loss measurements. To more complex methods

such as Half-cell Potential, Resistivity and Linear Polarisation measurements that

make use of electrochemical techniques to assess chloride induced corrosion.

These methods are well documented some of which are described and evaluated

below according to the corrosion property it assesses.

2.2 Presence of Corrosion

2.2.1 Visual Inspection

Visual inspection is the most basic method of assessing for the presence of

corrosion. It however needs to be conducted by trained inspectors and the criteria

for assessment should be as objective as possible.

As discussed previously corrosion results in a build-up of corrosion products around

the rebar. These corrosion products occupy up to 10 times (Broomfield, 1997) more

volume than the original metal from which they were derived. This generates the

tensile stresses causing cracking and spalling of the concrete cover (Figure 2-1).

The first indication of a problem is the formation of a crack along the reinforcement

accompanied very often by rust staining. This presents one of the limitations to

Figure 2-1 Cracking and spalling of cover concrete


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visual inspection is that corrosion is already in an advanced stage once cracking

starts and the structure would have already reached its service life at this point.

Visual inspection is also heavily reliant on the skill of the inspector and results such

as rust staining (due to various other causes other than reinforcement corrosion)

and different types of cracks can be misleading. Therefore visual inspection resultsmust be confirmed by testing to determine the source and cause of defects.

(Broomfield, 1997)

2.2.2 Half-cell Potential

Due to the electrochemical nature and macrocell formation indicative of chloride

induced corrosion different areas along the rebar are in different states of corrosion.

As a result the flow of ions through in the pore solution of the concrete also varies

over the concrete surface and results in potential (voltage) differences.

The use of half-cell potential as a method for assessing the presence or potential of

corrosion is widely used and described in ASTM C876 (2009) Standard test method

for half-cell potentials of uncoated reinforcing. In this method the potential difference

(voltage) between a reference electrode (in contact with the concrete surface) and

the steel embedded in the concrete is measured.

A voltmeter connected to the reference electrode and the embedded steel, as

detailed in Figure A-2 in Appendix A, measures the numeric value of voltage at

various positions on the concrete surface. The more negative the voltage the

greater the probability of corrosion. The probability of corrosion corresponding with

the different voltage ranges from ASTM C876 (using a Copper-Copper Sulphate

reference electrode) is presented in Table 2-1 compared with other referenceelectrodes cited by Broomfield (1997).

Copper-

Copper

Sulphate

Silver-Silver

Chloride

Calomel Standard

Hydrogen

Electrode

Probability of

Corrosion (%)

> -200 > -106 > -126 > 116 Less than 10

(Low)

-200 to -350 -106 to -256 -126 to -276 116 to -34 Uncertain

(Intermediate)

< -350 < -256 < -276 < -34 Greater than 90%

(High)

< -500 < -406 < -426 < 184- Severe corrosion

Broomfield (1997) also states that the corrosion potentials measured by the half-cellmethod can be misleading. In saturated conditions with no oxygen to form a passive

Table 2-1 Half-cell potential (voltage in mV) vs. probability of corrosion (ASTM876, 2009)


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layer and corrosion very negative potentials can be found. This is because the

method measures the thermodynamics of corrosion and not the rate of corrosion.

(Broomfield, 1997)

The resistivity of the concrete can also affect the accuracy of the half-cell potential

readings. It is only when the resistivity of the concrete is much larger than theresistance of the voltmeter that the true potential values are approached. (Otieno, et

al., 2010)

2.3 Corrosion Rate

Gowers and Millard (1999) states that the ionic flow of current between the anodic

and cathodic areas of the reinforcement are regulated by the electrical resistance of

concrete. The higher the concrete resistivity is the lower the current flowing

between anodic and cathodic areas and therefore the lower the corrosion rate.

2.3.1 Concrete ResistivityThe Wenner technique described by Gowers and Millard (1999) is most commonly

used to measure the resistivity of concrete. The measurement is done with a four-

probe resistivity meter with four equally spaced contacts placed on the concrete

surface as show in Figure 2-2.

A small AC current (I) is then passed between the two outermost contacts and the

resultant potential difference between the inner two contacts (V) measured. The

resistivity () of the concrete is then calculated using the equation as shown in

Figure 3-2 (Gowers and Millard, 1999). The interpretation of these resistivity

measurements from Langford and Broomfield (1987) are given below:> 20 kcm Low corrosion rate

Figure 2-2 Wenner technique for measuring resistivity (Gowers and Millard, 1999)


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10 20 kcm Low to moderate corrosion rate

5 10 kcm High corrosion rate

< 5 kcm Very high corrosion rate

Gowers and Millard (1999) states that this method should however be used withcare as significant errors can be obtained. The factors that contribute to these

errors, presented by Gowers and Millard (1999), are described in Table 2-2.

Factor causing error Description

Geometrical

constraints

If the dimensions of the concrete element being

measured are relatively small, the current is constricted

to flow into a different field pattern resulting in anoverestimation the resistivity of the concrete.

Concrete

non-homogeneity

Concrete contains aggregate particles and cement

paste with different resistivity measurements. If the

Wenner contact spacing is reduced the presence of a

high-resistivity aggregate particle immediately beneath

one of the surface contacts will result in a random

scatter in the repeatability of the measurement.

Poor surface contact

An uneven electrical contact between the two innercontacts and the surface of the concrete can lead to

false common mode voltages resulting in significant

errors.

Surface layers of

different resistivity

from the bulk

concrete

This causes distortion in applied current field. The

resultant effect depends on whether the surface layer

has a higher or a lower resistivity than that of the

underlying concrete. Greater errors were found with a

low resistivity to that of a surface layer with a high

resistivity.

Presence of steel

reinforcement

The current field is also distorted by the presence of a

steel reinforcing bar directly underneath the position of

measurement.

Ambient

environmental

conditions

The relationship between resistivity and air temperature

was found to be inversely linear. Thus as the air

temperature increased the resistivity of the same

concrete decreased.

Table 2-2 Factors causing errors in resistivity measurements (Gowers andMIllard, 1999)


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2.4 Extent of Corrosion

Despite the widespread use of the corrosion rate measurements discussed in the

previous section these cannot yet be used to calculate the total extent of the

corrosion in terms of steel section loss. (Broomfield, 1997) However it is possible to

measure how much steel is being oxidised and forming rust with techniques such

as Linear Polarisation.

2.4.1 Linear Polarisation

This method measures the current generated in the anodic and cathodic reactions

of a macrocell and converts the current flow, by Faradays law, to metal loss such

that 1A.cm-2 = 11.6m steel loss per year. (Broomfield, 1997)

Linear polarisation is achieved by polarising the steel reinforcement with an

electrical current and comparing it to the effect on the half-cell potential. A

schematic diagram of the linear polarization measurement device is given inAppendix A, Figure A-3 (Grantham, 2003).

The technique involves the measurement of the half-cell potential after which a

small current is transmitted from an auxiliary electrode to the reinforcement. The

half-cell potential is then measured with the transmitted current and the change in

half-cell potential recorded. The change in half-cell potential is the related to the

corrosion current which is in turn used to determine the corrosion condition over a

specific area of steel. (Broomfield, 1997)

The corrosion current (measured with a guard ring to confine the current to a known

area of reinforcement) and the associated corrosion condition from Broomfield, etal., (1994) is given below:

< 0.1A.cm-2 Passive condition

0.1A.cm-2 0.5A.cm-2 Low to moderate corrosion

0.5A.cm-2 1.0A.cm-2 Moderate to high corrosion

> 1.0A.cm-2 High corrosion

There are two main limitations (Broomfield, 1997) to Linear Polarisation. The first is

environmental conditions such as temperature and humidity both of which affect the

chloride induced corrosion process. Temperature affects the rate of oxidationreaction and relative humidity, moisture, enables the corrosion process to be

sustained.

The second is the determination of the surface area of the steel being measured.

With pitting corrosion the area of reinforcement can result in the underestimation of

the corrosion extent. (Broomfield, 1997)


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3. CASE STUDY: REHABILIATION BY USING IMPRESSED-

CURRENT CATHODIC PROTECTION

3.1 Introduction

This section describes the renovation and rehabilitation of bridges with extensive

chloride-induced reinforcement corrosion. This is presented in the form of a case

study of an article by R. Bottenberg published in Concrete International September

2008.

Bottenberg (2008) presented the successful rehabilitation of six legendry bridges on

the Oregon Coast Highway by Impressed-current Cathodic Protection (ICCP). This

method makes use of the electrochemical nature of chloride induced corrosion, as

described and discussed in previous sections, to protect and rehabilitate structures

already effected by corrosion.

This section will look briefly at the theory behind cathodic protection and discuss

how it was successfully used as described by Bottenburg (2008) to rehabilitate

bridges with chloride induced corrosion.

3.2 Cathodic Protection

As discussed previously macrocell corrosion, indicative of chloride attack, consists

of an anode and a cathode connected by a conductor and an electrolyte. Electrons

stripped from the Iron (steel) atoms flow from the anode to the cathode where they

combine with positive ions to form compounds such as hydrogen and water.

(Bottenberg, 2008)

Cathodic protection takes advantage of this compound formation at the cathode of a

macrocell by causing the previously anodic steel reinforcement to become cathodic.

The cathodic reaction causes the PH to increase resulting in the re-passivation of

the steel reinforcing bars.

There are two forms of cathodic protection namely sacrificial anode cathodic

protection (SACP) and impressed-current cathodic protection (ICCP). (Broomfield,

1997)

3.2.1 Sacrificial Anode Cathodic Protection

SACP is achieved through the formation of a galvanic cell by the wasting of a

sacrificial anode, liberating electrons which are transported to the cathode. The

wasting of the anode therefore protects the previously anodic steel reinforcement by

causing it to become cathodic.

3.2.2 Impressed-current Cathodic Protection

With ICCP an external power supply is connected to the steel reinforcement at the

one end and a permanent anode at the other. The power supply passes sufficient

current to cause the anodic reaction at the steel reinforcement to stop and make the

reaction cathodic. (Broomfield, 1997) ICCP was used to repair and rehabilitate the

bridges presented by Bottenberg (2008).


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3.3 Components of an Impressed-current Cathodic Protection System

Broomfield (2008) discusses several components, listed below, of an impressed-

current cathodic system to ensure its success.

Electrical continuity of the cathode (reinforcement) Minimal current supply

An anode distributed over the concrete surface

Gas permeability of the anode

Maintained moisture around the anode

Transformer/Rectifier to regulated DC input

Half-cells or other monitoring instrumentation

These components were incorporated by Bottenburg (2008) in the repair and

rehabilitation of six bridges on the Oregon Coast Highway as discussed below.

3.3.1 Preparation and Electrical ContinuityWork starts by sounding the entire concrete surface with a 450g hammer to locate

delaminated or spalling areas of concrete which are marked and removed using

pneumatic hammers. The exposed concrete and steel reinforcement is then treated

by abrasive blasting and extra steel added if the steel section loss is beyond limits.

The resistance across the rebar grid is then measured to ensure electrical continuity

and additional steel welded on in areas of high resistance (poor connectivity). Brass

terminals to connect the rebar to the current source are fixed to the reinforcement.

Reference silver-silver chloride cells are also installed for monitoring of the electrical

potential within the repaired area. This allows for the correct current to be suppliedensuring that the reinforcement becomes cathodic and concrete resistivity is

overcome.

3.3.2 Anode Installation

After the concrete is patched using a cement patching material the anode terminals

and plates, to which the current source is connected, is anchored into the concrete.

The zinc anode is then installed by arc spraying over the surface of the concrete

and the anode terminal plates ensuring complete distribution of the anode over the

surface of the concrete.

The arc sprayed zinc anode is highly conductive and porous allowing the

permeation of gases thorough it. It also has the advantage of being the same colour

as concrete but is however toxic (Broomfield, 1997) and should be used with the

necessary precaution.

3.3.3 Power Connection

With all the components of the ICCP system installed the anode (zinc surface

coating) and cathode (steel reinforcement) is then connected to the positive and

negative terminals of the DC power supply respectively.

The transformer, power regulation, monitoring, control and recording equipment areall housed in a cabinet (constructed from a corrosion resistant material).


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3.4 Challenges of Impressed-current Cathodic Protection

Despite the successful use of ICCP to repair and rehabilitate Six Oregon Coast

Highway Bridges, Bottenberg (2008) also describes some challenges that have

been experienced.

Localized anode failure attributed to the heat of a campfire and the de-bonding of

an anode as a result of high currents which were not regulated have been noted

highlighting the importance of current regulation as discussed by Broomfield (1997).

Further to this the build-up of corrosion products at the zinc concrete interface was

also noted causing an increase in electrical resistance and a decrease in pH

promoting further corrosion. This build-up of corrosion products is due to the

corrosion of the zinc which forms oxides and sulphates (Broomfield, 1997).

Power supply failure (even when placed in corrosion resistant enclosures) was also

experienced due the corrosive environment in which ICCP is implemented.Finally Bottenberg (2008) also noted the high cost ($936 per square meter) and

labour intensity of this method of repair and rehabilitation.

3.5 Conclusion

ICCP therefore, despite its successful use, has considerable challenges that need

to be considered when comparing it to other electrochemical repair and

rehabilitation techniques.


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4. REFERENCES

1. ASTM C876, 2009. Standard test method for half-cell potentials of uncoated

reinforcing steel in concrete. West Conshohocken: ASTM International.

2. Berke, N. S., 2006. Corrosion of Reinforcing Steel. In: Significance of Tests and

Properties of Concrete and Concrete-Making Materials - STP 169D. West

Conshohocken: ASTM International, pp. 164-173.

3. Bottenberg, R., 2008. Cathodic Protection of Historic Bridges - Technology helps

preserve legacies on the Oregon Coast Highway. Concrete International, September,

pp. 37-41.

4. Broomfield, J. P., 1997. Corrosion of Steel in Concrete - Understanding, Investigation

and Repair. London: E & FN Spon.

5. Broomfield, J., Rodriguez, J., Ortega, L. & Garcia, A., 1994. Corrosion RateMeasurements in Reinforced Concrete Structures by a Linear Polarization Device.

American Concrete Institute - Special Publication, Volume 151, pp. 163-182.

6. Domone, P., 2010. Part 2: Metals and Alloys . In: Construction Materials their Nature

and Behaviour (4th Edition). London : Spon Press, pp. 63-67.

7. Domone, P., 2010. Part 3: Concrete. In: Construction Materials their Nature and

Behaviour 4th edition. London: Spon Press, pp. 83-208.

8. Glass, G., 2003. Reinforcement Corrosion. In: J. Newman & B. S. Choo, eds.

Advance Concrete Technology - Concrete Properties. Oxford: Butterworth-Heinemann, pp. 9/1-9/27.

9. Glass, G., Reddy, B. & Buenfeld, N., 2000. The participation of bound chloride in

passive film breakdown on steel in concrete. Corrosion Science, Volume 42, pp.

2013-2021.

10. Gowers, K. & Millard, S., 1999. Measurement of Concrete Resistivity for Assessment

of Corrosion Severity of Steel Using Wenner Technique. ACI Materials Journal,

96(5), pp. 536-541.

11. Grantham, M., 2003. Diagnosis, inspection, testing and repair of reinforced concrete

structures. In: J. Newman & B. S. Choo, eds. Advanced Concrete Technology -Testing and Quality. Oxford: Butterworth Heinemann, pp. 6/1-6/54.

12. Langford, P. & Broomfield, J., 1987. Monitoring the corrosion of reinforcing steel.

Construction Repair, 1(No.2), pp. 32-36.

13. Otieno, M., Alexander, M. & Beushausen, H., 2010. Concrete Materials & Structural

Integrity Research Unit. [Online] Available at: http://www.csirg.uct.ac.za/[Accessed

30 August 2012].


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APPENDIX A

Figure A-1 Service-life model of reinforced concrete exposed to a corrosive environment(Domone, 2010)

Figure A-2 Reference electrode circuitry (ASTM C876, 2009)


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Figure A-3 Schematic diagram of the linear polarization measurement device (Grantham,2003)

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Assessment and Repair of Chloride Induced Corrosion of Steel in Reinforced Concrete

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