Fyp 1 progress report 2 half cell measurement for reinforce steel concrete %28 mohd izwan khalid%29

UNIVERSITI TENAGA NASIONAL BACHELOR OF MECHANICAL ENGINEERING (HONS)

Author Student ID

Mohd Izwan Khalid b Mohd Supian ME 087189

Code MPRB 412 (Progress Report 2)

Supervisor 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

1st Week

Date due in

16th December 2013

Date received

Assessed date

ASSESSMENT OF REINFORCING STEELS IN CONCRETE BY USING NDT (HALF-CELL POTENTIAL)

MPRB 412 - PROGRESS REPORT 2 REV NO : 000

DATE : 15 DECEMBER 2013

Progress report 2 | MPRB 412 P a g e | i

LIST OF CONTENT

ITEM DESCRIPTION PAGE

1 INTRODUCTION ................................................ 1 1.1 Background study ................................................ 2 1.2 Literature review ................................................ 5

2 WORK COMPLETED ................................................ 6

3 PROBLEMS ................................................ 6

4 METHODOLOGY ................................................ 7 4.1 Experiment 1 procedure ................................................ 7 4.2 Experiment 2 procedure ................................................ 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




Progress report 2 | MPRB 412 P a g e | 1

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 : Specification for Plain Steel Wire for Concrete Reinforcement ASTM A184/A184M : Specification for Fabricated Deformed Steel Bar Mats for Concrete

Reinforcement ASTM A185 : Specification for Welded Plain Steel Wire Fabric for Concrete

Reinforcement ASTM A496 : Specification for Deformed Steel Wire for Concrete Reinforcement ASTM A615/A615M : Deformed and plain carbon-steel bars for concrete reinforcement ASTM A767/A767M : Specification for Zinc-Coated(Galvanized) Steel Bars for Concrete

Reinforcement ASTM A934/A934M : Specification for Epoxy-Coated Prefabricated Steel Reinforcing Bars ASTM A996 : Rail-steel and axle-steel deformed bars for concrete reinforcement ASTM A1035 : 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





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.





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.





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]

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.

0.0007 mm for internal crack 0.0032 mm for Internal Penetration

0.0045 mm for External Cracking 0.0049 mm for External Cracking





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]





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. Obtaining Nuclear Agencies of Malaysia concrete grade measurement; G10, G15, G20, G25, G30, G35, G40 and G45 from Mr. Azreen

II. Discussing with Mr. Azreen about the detailed methodology on the experiment as per industrial standard

III. 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.

IV. Request assistant from material lecturer Mr. Zainuddin Yahya for the investigation of material corrosion rate

V. Early communication has been made with the technician who responsible in keeping the EuroCell™ Electrochemical Cell Kit, Gamry Instrument for corrosion rate investigation

VI. 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

VII. 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.





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)





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)





Normal water

For normal water, the study will use the normal tap water that being used in Malaysian daily life

II. Put each water in pail of close basin III. Obtaining pieces of steel rebar from Nuclear Agency of Malaysia; total

number of 48 specimen IV. Put 12 specimen in each pail of basin V. Set up the Gamry EuroCell™ kit and observe the corrosion process for 3 days

to predict the corrosion pattern to each specimen VI. If the corrosion process is at lower rate, it is best to check the rate weekly

depends on the situation VII. 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. 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

II. 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

III. The dimension for the cube and the embedded rebar steel are as per below:

IV. The concrete are left to dry for about 1 or 2 days V. The cube will be divided into a few identified points and the half cell

measurement of corrosion will be taken from the points identified. VI. All results were recorded into the table as per Attachment 3

150 mm

150 mm

150 mm

50 mm

75 mm

ISOMETRIC VIEW

TOP VIEW





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) Reference Electrode (Cu/CuSO4) b) Reinforcing steel rebar c) Concrete mixture d) Digital voltmeter

II. 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.





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.





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.





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. Dr. Abdul Aziz (FYP Supervisor) b. Mr. Zainuddin Yahya (Material Lecturer) c. Dr. Syukri Mohd (Industrial Supervisor) d. Mr. Noor Azreen (Industrial Supervisor)

APPENDIX 1

(Gantt Chart for FYP 1 and 2)

Gantt Chart for Final Year Project 1

FINAL YEAR PROJECT 1

Month October November December January

Item \ Week 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

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

Gantt Chart for Final Year Project 2 ** All experiment are planned to be conducted during short semester

FINAL YEAR PROJECT 2

Month June July August September

Item \ Week 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

Result analysis

Redo testing

Finalize analysis

Progress report 3

Comparison of data

Discussion

Slide preparation

Oral Presentation

Thesis compilation

Logbook write up

APPENDIX 2 (Mixture of concrete grade according to

Nuclear Agencies)

APPENDIX 3 (Result table)

Water type Concrete Gred Corrosion Rate (%)

0 20 40 60 80 100

Seawater

G10

G20

G30

G40

River water

G10

G20

G30

G40

Salt marsh

G10

G20

G30

G40

Normal water

G10

G20

G30

G40

Fyp 1 progress report 2 half cell measurement for reinforce steel concrete %28 mohd izwan khalid%29

Education

sources google

radial compression

salt marsh

radial expansion

concrete reinforcement

reinforced

radial expansion

pit depth