Citation
Corrosion of steel members strengthened with carbon fiber reinforced polymer sheets

Material Information

Title:
Corrosion of steel members strengthened with carbon fiber reinforced polymer sheets
Creator:
Bumadian, Ibrahim ( author )
Place of Publication:
Denver, CO
Publisher:
University of Colorado Denver
Publication Date:
Language:
English
Physical Description:
1 electronic file (155 pages). : ;

Subjects

Subjects / Keywords:
Carbon fiber-reinforced plastics ( lcsh )
Iron and steel bridges -- Corrosion -- Prevention ( lcsh )
Steel, Structural ( lcsh )
Genre:
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

Notes

Review:
Due to many years of service at several cases of exposure at various environments there are many steel bridges which are in need of rehabilitation. The infrastructure needs upgrading, repair or maintenance, and also strengthening, but by using an alternative as retrofits methods. The alternative retrofit method, which used fiber reinforced polymer (FRP) composite materials which their strength materials comes largely from the fiber such as carbon, glass, and aramid fiber. Of the most important materials used in the rehabilitation of infrastructure is a composite material newly developed in bonded externally carbon fiber and polymer (CFRP) sheets, which has achieved remarkable success in the rehabilitation and upgrading of structural members. This technique has many disadvantages one of them is galvanic corrosion. This study presents the effect of galvanic corrosion on the interfacial strength between carbon fiber reinforced polymer (CFRP) sheets and a steel substrate. A total of 35 double-lap joint specimens and 19 beams specimens are prepared and exposed to an aggressive service environment in conjunction with an electrical potential method accelerating corrosion damage. Six test categories are planned at a typical exposure interval of 12 hours, including five specimens per category for double-lap joint specimens. And six test categories are planned at a typical exposure interval of 12 hours, including three specimens per category for Beam section specimens. In addition one beam section specimen is control. The degree of corrosion is measured. Fourier transform infrared (FTIR) reflectance spectroscopy has been used to monitor and confirm the proposed corrosion mechanisms on the surface of CFRP. In this study we are using FTIR-spectroscopic measurement systems in the mid infrared (MIR) wavelength region (4000 - 400) cm-1 to monitor characteristic spectral features. Upon completion of corrosion processes., all specimens are monotonically loaded until failure occurs to measure their residual capacity. A relationship between the level of galvanic corrosion and the failure characteristics of steel-composite interface is established.
Thesis:
Thesis (M.S.)--University of Colorado Denver. Civil engineering
Bibliography:
Includes bibliographic references.
General Note:
Department of Civil Engineering
Statement of Responsibility:
by Ibrahim Bumadian.

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Source Institution:
University of Colorado Denver
Holding Location:
|Auraria Library
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
903696969 ( OCLC )
ocn903696969

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i C ORROSION OF STEEL MEMBERS STRENGTHENENED WITH CARBON FIBER REINFORCED POLYMER SHEETS By IBRAHIM BUMADIAN B.S., Omar Al Mukhtar University, 20 02 M .S., Academy of Graduate Studies Benghazi, 2007 A thesis submitted to the Faculty of the Graduat e School of the University of Colorado in partial fulfillment of the requirements for the degree of Master of Science Civil Engineering 201 4

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ii 201 4 IBRAHIM BUMADIAN ALL RIGHTS RESERVED

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iii This thesis for the Master of Science degre e by Ibrahim Bumadian has been approved for the Civil Engineering Program By Yail Jimmy Kim, Chair Cheng Yu Li Nien Yin Chang November 21 201 4

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iv Bumadian Ibrahim (M.S. Civil Engineering) Corrosion of Steel Members Strengthe ned with Carbon F iber Reinforced Polymer Sheets. Thesis directed by Associate Professor. Yail Jimmy Kim A BSTRACT Due to many years of service at several cases of exposure at various environments there are many of steel bridges which are in need of rehabilitation. The in frastructure needs upgrading, repair or maintenance, and also strengthening, but by using an alternative as retrofits methods. The alternative retrofit method which used fiber reinforced polymer (FRP) composite materials which their strength materials com es largely from the fiber such as carbon, glass, and aramid fiber. Of the most important materials used in the rehabilitation of infrastructure is a composite material newly developed in bonded externally carbon fiber and polymer (CFRP) sheets, which has a chieved remarkable success in the rehabilitation and upgrading of structural members. This technique has many disadvantages one of them is galvanic corrosion This study presents the effect of galvanic corrosion on the interfacial strength between carbon f iber reinforced polymer (CFRP) sheets and a steel substrate. A total of 35 double lap joint specimens and 19 beams specimens are prepared and exposed to an aggressive service environment in conjunction with an electrical potential method accelerating corro sion damage. Six test categories are planned at a typical exposure interval of 12 hours, including five specimens per category for double lap joint specimens And six test categories are planned at a typical exposure interval of 12 hours including three

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v s pecimens per category for Beam section specimens In addition one beam section specimen is control. The degree of corrosion is measured. Fourier transform infrared (FTIR) reflectance spectroscopy has been used to monitor and confirm the proposed corrosio n mechanisms on the surface of CFRP In this study we are using FTIR spectroscopic measurement systems in the mid infrared (MIR ) wavelength region (4000 400) cm 1 to monitor characteristic spectral features. Upon completion of corrosion processes, all s pecimens are monotonically loaded until failure occurs to measure their residual capacity. A relationship between the level of galvanic corrosion and the failure characteristics of steel composite interface is established. The form and content of this ab stract are approved. I recommend its publication. Approved: Yail Jimmy Kim

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vi ACKNOWLEDGEMENTS I appreciate the inspiration, guidance, and assistance of many people without whom this work would not have been possible. Associate Professor Yail Jimmy K im my thesis advisor, provided guidance and support not only for this thesis, but also in my professional development. I would also like to thank the department chair, committee chair and committee members of civil engineering for providing generous and support along the way I would like to thank my fellow student at the University of Colorado Denver for their support, encouragement, assistance, and friendship. Abulrhma Namru, Shallah Alwkeel, Thushera, and Abdulsameea Alfed. I also would like to th ank the Chemical Department of University of Colorado Denver for their assistance. A special thanks goes to Deines for her assistance in the FTIR work. I am also thankful to the technical team of the Faculty of Engineering Department, who helped me compl ete the experimental work and to all the staff and graduate students at UCD for sharing ideas, discussion and friendship. I would like to thank all the members of our lab Tom, Jack, and Eric I would like to thank the Libyan government, especially the Mini stry of Higher Education and CBIE for nominating me to study aboard and supporting me and my family with a fully funded scholarship.

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vii Finally, I must take the opportunity to acknowledge and thank my parents for their endless love and support. They have impl anted in me high work ethics and confidence to prosper. I would like to thank my brothers and sisters for standing by my parents when I am gone. I am indebted and very grateful to my wife Amira for her support and encouragement throughout my learning journ ey at UCD.

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viii TABLE OF CONTENTS Chapter 1. Introduction ................................ ................................ ................................ .................. 1 1.1 Background ................................ ................................ ................................ ............... 1 1.2 Researc h Significance ................................ ................................ ............................... 3 1.3 Scope of Research ................................ ................................ ................................ ..... 4 1. 4 Contributions ................................ ................................ ................................ .............. 4 1.5 Outline of the Thesis ................................ ................................ ................................ .. 5 2. Literature Review ................................ ................................ ................................ ............. 7 2.1 Rehabilitation of Steel Structures ................................ ................................ .............. 7 2.2 Background of Rehabilitation Techniques ................................ ................................ 8 2.3 Types of FRP Composites and Applications ................................ ........................... 14 2.3.1. FRP Composite ................................ ................................ .............................. 14 2.3.2. Types of FRP ................................ ................................ ................................ 15 2.3.3. Properties of FRP ................................ ................................ ........................... 1 9 2.3.4. FRP Application on Rehabilitation ................................ ................................ 28 2.4 Corrosion Effect ................................ ................................ ................................ ...... 29 2.5 Fourier Transformaion Infrared Spectroscopy (FTIR) ................................ ............ 30 2. 6 Summary and Conclusion ................................ ................................ .......................... 3 2 3. Behavior of Corrosion for Interface T est Specimen ................................ ...................... 3 3 3.1 Fabri cation and Specimen Design ................................ ................................ .......... 3 3 3.1.1 General Overview ................................ ................................ .......................... 3 3 3.1.2 Materials ................................ ................................ ................................ ......... 3 3

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ix 3.1.3 Preparation ................................ ................................ ................................ ...... 3 4 3.1.4 Test Specimen ................................ ................................ ................................ 3 5 3.1.5 Corrosion Exposure ................................ ................................ ........................ 3 5 3.2 Corrosion Testing ................................ ................................ ................................ .... 3 6 3.2.1 Mass Loss Method ................................ ................................ .......................... 3 6 3.2.2 a w M e thod ................................ ................................ ................... 3 7 3. 2 3 Fourier Transformed Infrared Spectra FTIR Method ................................ ..... 3 7 3. 3 Mechanical Testing ................................ ................................ ............................... 3 8 3. 3 1 Capacity of L oding ................................ ................................ ....................... 3 8 3. 3 2 Strain G age R eading ................................ ................................ ..................... 3 9 3. 4 Experimental Results ................................ ................................ ............................ 3 9 3. 4 .1 Analysis of Corrosion ................................ ................................ .................. 3 9 3. 4 .2 Load D isplacement Response ................................ ................................ ...... 4 1 3. 4 3 Strain Gage Response ................................ ................................ .................. 4 2 3. 4 4 Failure Mode of Interface Test Specimen ................................ .................... 4 2 3. 5 Summary and Conclusion ................................ ................................ .................... 4 3 4. Behavior of Corrosion for Beam Test in Flexure ................................ .......................... 7 4 4.1 Fabrication and Specimen Design ................................ ................................ ......... 7 4 4.1.1 General Overview ................................ ................................ ......................... 7 4 4.1.2 Materials and Preparation ................................ ................................ ............. 7 4 4.1.3 Test Specimen ................................ ................................ ............................... 7 6 4.1.4 Corros ion Exposure ................................ ................................ ...................... 7 6 4.2 Corrosion Testing ................................ ................................ ................................ ... 7 7

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x 4 .2.1 Mass Loss Method ................................ ................................ ........................ 7 7 4 .2.2 a w Mathod ................................ ................................ ................. 7 8 4 2 3 Fourier Tr ansformed Infrared Spectra FTIR Method 7 8 4.3 Mechanical Testing ................................ ................................ ............................... 7 9 4. 3.1 Capacity of Loading ................................ ................................ ....................... 7 9 4 3. 2 Straine Gage Read ing ................................ ................................ .................... 80 4. 4 Experimental Results ................................ ................................ ............................. 80 4. 4 .1 Analysis of Corrosion ................................ ................................ ................... 80 4. 4 .2 Load Displacement Response of the Beam Test ................................ ......... 8 2 4. 4.3 Strain Gage Response of the Beam Test ................................ ........................ 8 3 4. 4. 4 PI Gage Response of the Beam Test ................................ .............................. 8 4 4. 4 5 Failure mode of Beam T est S pecimen ................................ ........................... 8 4 4. 5 Summary and Conclusion ................................ ................................ ..................... 8 6 5 Conclusion and Recommendation ................................ ................................ ............... 1 2 6 5.1 Conclusions on Interface test Specimen Behavior ................................ ............... 1 2 6 5.2 Conclusions on Beam Test in Flexure B ehavior ................................ .................. 1 2 7 5 3 Recommendation for Future Work ................................ ................................ ...... 1 2 9 References ................................ ................................ ................................ ........................ 1 3 1 Appendix A ................................ ................................ ................................ ................................ ...... 1 3 6 B ................................ ................................ ................................ ................................ ..... 1 40 C ................................ ................................ ................................ ................................ ..... 1 4 1

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xi LIST OF TABLES Table (Adapted from ACI 440.2R 08) 29 2.2. Sections of infrared emission and corresponding energy tra nsitions ......................... 3 1 3.1 Material properties from manufacturer ................................ ................................ ........ 4 4 3.2 Test matrix ................................ ................................ ................................ ................... 4 4 3.3 Test specimens for electrical cell ................................ ................................ ................. 4 5 3.4 Corrosion rate by mass loss and Faraday law ................................ .............................. 4 6 3.5 Test results of specimens ................................ ................................ ............................. 4 7 4.1 (a) Test matrix ................................ ................................ ................................ ............... 8 7 4.1 (b) Test matrix ................................ ................................ ................................ ............... 87 4. 2 Test specimens for electrical cell ................................ ................................ ................. 8 8 4.3 Corrosion rate by mass loss and Faraday law ................................ .............................. 8 9 4.4 Test results of specimens ................................ ................................ ............................. 90

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xii LIST OF FIGURES Figure 1.1 View of accelerated corrosion on the surface of a bridge support beam made from weathering steel ( By Ronald F. Kulak, et al 2011) ................................ ............................. 1 1.2 Strengthening of a steel bridge with CFRP ................................ ................................ .... 2 2.1. Reparation of the badly corroded section (Tilly G.P., 2008). ................................ .... 10 2.2. Corroded bottom flange is replaced (Tilly G.P., 2008). ................................ ............ 11 2.3. AFRP (a) tendons and (b), lam inates ................................ ................................ ......... 16 2.4. GFRP size ................................ ................................ ................................ ................... 16 2.5. CFRP (a) tendons, (b) laminates, (c) sheet ................................ ................................ 1 8 2.6. Stress strain relationship for FRP and steel ................................ ............................... 20 3.1 Substrate preparation ................................ ................................ ................................ .. 4 8 3.2 Preparation of a specimen before bonding ................................ ................................ .. 4 8 3.3 Interface test specimens: ( a ) mixing an epoxy adhesive ; ( b ) mark adhesive place ; ( c) epoxy bonding ; ( d ) after curing. ................................ ................................ .............. 4 9 3. 4. Setup for accelerated corrosion testing :(a) schematic ; (b) test picture ..................... 49 3. 5 Measuring weight of specimen: (a) before corrosion; (b) after corrosion .................. 50 3.6 Comparison of specimens: (a) before corrosion ;(b) after the corrosion .................... 5 1 3.7 Tension test: (a) strain gages ; (b)stra in monitoring;(c)displacement monitoring ...... 5 1 3.8 FTIR machine for chemical investigations ................................ ................................ 5 2 3. 9 Variation of cur rent surface area with time ................................ ................................ 5 2 3. 10 Variation of mass loss with time ................................ ................................ ............... 5 3 3. 11. Variation of potential ................................ ................................ ................................ 5 3 3. 12. Variation of current density with time ................................ ................................ ...... 5 4 3.1 3 Corrosion Rate obtained by the Loss of Mass Method ................................ ............. 5 4

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xiii 3.1 4 Method ................................ ............................... 5 5 3.1 5 .................. 5 5 3. 16. Test specimens For FTIR : (a) at 0 Hr ; (b) at 12 Hr ; (c) at 24 Hr ; (d) at 36 Hr ; (e) at 48 Hr ; (f) at 60 Hr ; (g) at 72 Hr ................................ ................................ .................. 5 8 3. 17. Comparison of FTIR for al l specimens ................................ ................................ .... 5 9 3. 18 Test results of specimens ................................ ................................ .......................... 60 3. 19 Load displacement of specimens bonded with epoxy: (a) at 0 Hr ; (b) at 12 Hr ; (c) at 24 Hr ; (d) at 36 Hr ; (e) at 48 Hr ; (f) at 60 Hr ; (g) at 72 Hr ................................ ........ 6 4 3. 20 Comparison of load displacement f or all specimens ................................ .............. 6 4 3. 21 Load strain behavior of specimence: (a) No corrosion: strain gages 1 4 ; (b) After 12 Hr : strain gages 1 4 ; (c) at 24 Hr: strain gages 1 4 ; (d) at 36 Hr : strain gages 1 4 ; (e) at 48 Hr : strain gages 1 4 ; (f) at 60 Hr : strain gages 1 4 ; (g) at 72 Hr : strain gages 1 4 ................................ ................................ ................................ ........................ 6 8 3. 2 2 St rain devlopment along of CFRP : (a) No corrosion: strain gages 1 4 ; (b) After 12 Hr : strain gages 1 4 ; (c) at 24 Hr: strain gages 1 4 ; (d) at 36 Hr : strain gages 1 4 ; (e) at 48 Hr : strain gages 1 4 ; (f) at 60 Hr : strain gages 1 4 ; (g) at 72 Hr : strain gages 1 4 ................................ ................................ ................................ ........................ 7 2 3.2 3 Failure mode of the interface test ................................ ................................ .............. 7 3 4.1 Beam details and test setup ................................ ................................ ......................... 9 1 4.2 Beam preparation: (a) cutting the beam; (b) grind the beam; (c) clean t he surface; (d) flange cut. ................................ ................................ ................................ .................... 9 2 4.3 Preparation of a specimen before bonding: (a) p recut CFRP sheets; (b) prepared beams ................................ ................................ ................................ ................................ 9 2 4.4 Beam test specimens: (a) mixing an epoxy adhesive; (b) epoxy bonding; (c) after curing ................................ ................................ ................................ ................................ 9 3 4. 5. Setup for ac celerated corrosion testing :(a) schematic; (b) test picture ...................... 9 3 4.6 Measuring dimensions of specimen: (a) thickness of flange; (b) total depth; (c) thickness web (d) width flange ................................ ................................ .......................... 9 4 4. 7. Measuring weight of specimen: (a) before corrosion; (b) after c orrosion .................. 9 4

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xiv 4.8 Comparison of specimens: (a) after 12 Hr ; (b) after 24 Hr; (c) after 36 Hr ; (d) after 48 Hr ; (e) after 60 Hr ; (f) after 72 Hr. ................................ ................................ ............ 9 5 4 .9 Flexural test ................................ ................................ ................................ ................. 9 6 4.10 Strain gages for tension flange ................................ ................................ .................. 9 6 4.1 1. Variation of current surface area with time ................................ .............................. 9 7 4.1 2. Variation of mass loss with time ................................ ................................ ............... 9 8 4.1 3 Variation of potential ................................ ................................ ................................ 9 8 4.1 4 Variation of current density with time ................................ ................................ ...... 9 9 4.15 Corr osion Rate obtained by the Loss of Mass Method ................................ ............. 9 9 4.16 ................................ ............................. 100 4.17 ................ 100 4. 18. Test specimens For FTIR: (a) Contorol beam (b) After 12 Hr; (c) at 24 Hr; (d) at 36 Hr; (e) at 48 Hr; (f) at 60 Hr; (g) at 72 Hr. ................................ ...................... 10 4 4. 19. Comparison of FTIR for all specimens ................................ ................................ ... 10 5 4. 20 Test results of specimens ................................ ................................ ........................ 10 6 4. 21 Load displacemant behavior of specimence:; ( a) contorol beam ; (b) after 12 Hr; (c) a fter 24 Hr; (d) after 36 Hr ; (e) after 48 Hr ; ( f) after 60 Hr; (g) after 72 Hr ....... 10 9 4. 2 2 Load strain behavior of specimence: (a) control beam 0 Hr : strain gages 1 6; (b) After 12 Hr : strain gages 1 6; (c) at 24 Hr: strain gages 1 6; (d) at 36 Hr : strain gages 1 6 ; (e) at 48 Hr : strain gages 1 6 ; (f) at 60 Hr : strain gages 1 6 ; (g) at 72 Hr : strain gages 1 6. ................................ ................................ ................................ .............. 1 1 3 4.2 3 S train devlopment along of CFRP : (a) control beam 0 Hr; (b) After 12 Hr; (c) at 24 Hr ; (d) at 36 Hr; (e) at 48 Hr; (f) at 60 Hr; (g) at 72 Hr. ................................ ................ 1 1 6 4.2 4 Load PI Gages behavior of specimence: (a) Contorol beam (b) After 12 Hr; (c) at 24 Hr; (d) at 36 Hr; (e) at 48 Hr; (f) at 60 Hr; (g) at 72 Hr. ................................ ......... 1 20 4.2 5 Load crack mouth opening displacement: (a) Contorol beam (b) After 12 Hr; (c) at 24 Hr ; (d) at 36 Hr; (e) at 48 Hr; (f) at 60 Hr; (g) at 72 Hr ................................ .............. 1 2 4 4.26. Failure mode of beam: (a) fracture crack; (b) CFRP debonding. .......................... 1 2 5

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1 1. Introduction 1.1 Background The construction of steel is considered to be crucial in most countries around the world. Steel when used and protected against exposures environment, became serve, reliability and durability enough for the function that it was designed for it. The number of steel bridges of the infrastructures that have deteriorate d in service and need of repair and rehabilitation multiplied over the past years. The damage to structures might result from several sources, inclusive of faulty design and construction practices that they ignorant of the dangers involved of the environme ntal influence, overweight that must be used to loading, fires of construction, and galvanic corrosion of steel. Corrosion is critical to study because can lead to weak in strength and reliability of the structural. The corrosion decreases the total area o f the member in a steel structure that leads to increase in stress around the corroded area because there is an inverse relationship between cross section of steel area and stress. Figure 1.1 shows the influence of corrosion on steel members. Figur e 1 .1 V iew of accelerated corrosion on the surface of a bridge support beam made from weathering steel (By Ronald F. Kulak, et al 2011)

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2 In United States there are thousands of the highways of the steel bridges that have deterio rated due to environmental impact and require large expenditures to rehabilitation. Carbon fiber reinforced polymer (CFRP) has been newly used for the rehabilitation to infrastructure of steel members in the steel bridges and others of constructors buildin g of steel, in which the high reliability must be keep during the long time of service. The basic concept of rehabilitation steel members with CFRP materials is to strengthen these members with sheets of CFRP that are adhered to steel surface with epoxy gl ue. Consequently, it is forecasted that the accelerated testing methodology for the long time life forecast of composite structures exposed under the actual environments of various established like as corrosion effect at steel with CFRP. Figure 1. 2 shows b ridge girder rehabilitation with CFRP Figure 1.2 Strengthening of a steel bridge with CFRP The only disadvantage of the rehabilitation method with CFRP is galvanic corrosion that is a result of the high electric conductivity of CFRP when contacts to steel members. Galvanic corrosion can only happen when these three factors are available (Francis, 2000): an electrolyte like salt water linking the two materials (CFRP and steel), an electrical connection between the materials, and a sustained cathode reaction on the carbon.

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3 Removing any one of those factors prevents this problem. Thus in this study, focusing to get the s e factors together in experimental program The degree of corrosion measured. Upon completion of corrosion processes, all specimens are monotonically loaded until failure occurs to measure their residual capacity. The relationship between the level of galvanic corrosion and the failure characteristics of all specimens established. As results indicate that if corrosion occurs, the behav ior between the steel and CFRP degraded. 1.2 Research Significance This study presents an on going researches program concerning the performance of CFRP with steel members that should be performance subjected to galvanic corrosion effect. The objectives of t his research were: 1 Investigate the corrosion issue that may happen in steel structures with FRP composites. 2 The study prove information about behavior between the steel and CFRP to conform the loss of durability. 3 Investigate the adhesive bond CFRP experi mentally with interface steel stripe exposure to galvanic corrosion. 4 To examine experimentally the mechanical properties during different periods of time of exposure to corrosion to study the efficiency after the corrosion.

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4 1.3 Scope of Research The applic ation of CFRP in rehabilitation and strengthening steel bridges researched in recent years. Many of studies have focused on using CFRP composites to solving the problem of corrosion in constructors of bridges. Therefore, this study has concentrated on beha vior of corrosion during a period of rehabilitation. This thesis studied with a major part is critical is the corrosion that affects especial steel structures. This part was chosen to simulate real environmental conditions for experimental research, in add ition to providing additional useful information for future research. Therefore, the performed work through this thesis participated experimental testing of corrosion that created as a deficiency in the cross sectional area of steel members by using the corrosion cell. During different times from exposure to corrosion starting from 12 Hr to 72 Hr. wherever possible some of the experimental results of measurement of corrosion compared by different methods to calculate and analyzes the corrosion. 1.4 Contributi ons It is expected that this thesis makes a significant contribution to the rehabilitation of infrastructure by using CFRP application in civil, engineering of materials, and mechanical engineering due to it paves to use another new technical. It might be essential contributions as following: 1. Providing directives regarding using CFRP in rehabilitation in difficult environments as corrosion.

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5 2. Limited studies in this difficult environment which makes the strength and the durability of the bond between CFRP and steel in rehabilitation of infrastructure largely unknown. 3. Study the ability of the bond between CFRP and steel when corrosion happens after repairing to continue to exist a long time or not. 1.5 Outline of the Thesis This thesis includes five chapte rs. Literature review on the background of rehabilitation and techniques which have been used in this area is presented in chapter 2. The types of FRP composites and applications and corrosion effect at CFRP in addition to explaining applications FTIR are discussed in this chapter. Chapter Three, an overview of the experimental program of the interface of steel bond with CFRP and explains properties to all materials that are used during the test. In addition, this chapter includes the experimental steps th at have been conducted to find the effect of corrosion and also all measurements that have related its. Chapter Four presents the bond performance of behavior of steel beam at corrosion. Additional mechanical properties testing and FTIR for chemical inves tigations of different types of exposure are also tested. Chapter Five provides a summary from this experimental study and some recommendations for further experiments in this research area based on the evaluation of the results from the testing program.

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6 Appendix A presents additional detailed pictures of the process for the CFRP with Steel testing that have been done in which you can see the test setup. Appendix B presents the bond performance of the corrosion in which you can see the failure mode from the pictures. Appendix C presents the bond performance of characteristic Infrared Absorption Frequencies.

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7 2. Literature Review 2.1 Rehabilitation of Steel Structures definition Rehabilitation is the act of restoring anything to its original st ate; as the rehabilitation of the structural member which does not meet the design requirements to the specific performance level. There are two main categories for rehabilitation: repair and strengthening. Repair is the rehabilitation of a damaged struct ure or a structural member with the aim of bringing the capacity back to the pre damage level or higher. Strengthening is the increasing of the existing capacity of non damaged structure (or a structural member) to a specified level. In USA about 40 % of the highway bridges need repair or replacement, due to deterioration, structurally and functionally (Fickelhorn, M., 1990). In addition, about $ 120 billion per year is spent on rehabilitation due to corrosion losses in USA (Chong, K.P.,1998). Consequently the structural upgrade is required to increase the capacity of many existing structures. Moreover, parts facilitating expansion/ contraction of the bridge including load transfer to the sub structure, such as expansion joints & bearings, may also need re habilitation or replacement over time.

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8 2.2 Background of Rehabilitation Techniques In the past, several rehabilitation traditional retrofit techniques have been developed and used to achieve each desired improvement for repairing corroded steel members, some of the most common methods are: 1 Corrosion removal and surface cleaning The preparation work of the material surfaces could be divided into several categories, depending on national and international standards or codes. The grades of the surface preparation given below are in use in some countries (Radomski W., 2002). Grade I all impurities rust, and mill scale removed. The surface of the cleaned component shall be of metal, uniform and have silvery grayish look. Grade II all impurities rust and mill scale removed. A gray oxide layer is tolerable to stay between a metal substrate and a mill scale. The allowable limitation of the mill scale is 5% of the area of the cleaned steel surface. The appearance of the cleaned surface is matt and gray. Grad e III all impurities, the allowable limitation of the mill scale is 20% of the area of the cleaned steel surface. The surface of the cleaned component is non uniform, and some parts are metallic and other parts in different colures. Surface preparation of material in Grade I could be accomplished by sand or shot blasting and etching. Grade II by sand or shot blasting, hammering, brushing or flame cleaning (also

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9 called thermal method) and Grade III by hammering, brushing or scraping. The hand cleaning proce ss is done by brushing, hammering, scraping and grinding. It is low efficient and applicable to the small surfaces. Other methods (e.g. blasting) can be applied to larger surfaces and is more efficient. The most usual blasting cleaning methods are namely : 1 Dry abrasive blast cleaning. 2 Wet abrasive air blast was cleaning. 3 Water blast cleaning with or without abrasive. So, it should be emphasized that corrosion removal and surface cleaning are influencing the behavior of the anti corrosion protectio n. Therefore, the technical requirements should be followed and met carefully. When corrosion occurs and is localized, it is possible to repair this corroded material by removing the corrosion and keep the original and sound material or replace the corrode d material. When a replacing method taken, attention should be paid to load redistributions in the structure under operation. Removed member can cause additional stress to the neighboring elements, and this should be considered in analyzes. In Figure 2.1, it shows how the localized corrosion is repaired (Tilly G.P., 2008); During the repair process, strengthening of some sections might be required when the corroded flange is replaced. This example can be seen Figure 2.2.

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10 Figure 2.1 Reparation of the b adly corroded section (Tilly G.P., 2008)

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11 Figure 2.2 Corroded bottom flange is replaced (Tilly G.P., 2008) 1 Replacement of structural members A structural member, whole bridge or bearings, can be replaced due to damage as long as a repair proces s is not an economic and not technically feasible. The main idea behind repair process is that a new structural member manufactured in the factory and then installed or assembled in the current bridge. In this process, galvanic corrosion between the new an d old structural member can occur. Therefore, this problem should be considered and avoided. Another issue is jointing, for instance if welding is chosen the welded ability of the existing structural member should investigate. Welds and high strength frict ion grip bolts are mostly used to join the old and new structural member. Cutting of the damaged member from the existing bridge causes redistribution of the internal loads and consequently the geometry of members in the bridge can change. Therefore, this should be investigated and analyzed. In such cases, if necessary, hydraulic

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12 jacks, power winches, etc. can be used to support the existing bridge temporarily (Radomski W. 2002). Although, the traditional retrofit techniques has been used to repair corrode d steel members by using connected to steel plates through bolts or welding for these members, there are many disadvantages associated with this method, such as; (1) These methods must use more laborers and take a long time, (2) Also, these methods have r equired drilling and extensive (3) In addition, sometimes, bridge has to be closed to the traffic (4) Also, do not forget the increasing in the weight of members that repaired that would be to lead for deficiency in member capacity and increases in deflec tion. The aforesaid disadvantages of using the traditional technique to rehabilitation to steel structures and the fact that the requirement for the infrastructures become gradually high. And also, severe have promoted engineers and researchers to obligat e themselves to search for a better and more innovative solution. 2 Rehabilitation Using Fiber Reinforced Polymer (FRP) Composites Materials The advancement made in the Characteristics of composite materials that known as fiber reinforced polymers (F RP) and the development made in the adhesives have rendered them the ideal combination that may provide a better. In addition, more innovative solution for many structural problems such as rehabilitation. Newly the civil engineering has a new application w hich is FRP material. However, FRP materials have used in many applications of engineering such as aircraft, automobile, and chemical apparatus. In

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13 addition, it has been used in many of new industries as well as in aeronautical for quite long time. FRP mat erials have superior properties such as high tensile strength, very low weight to tensile ratio. For example, since the bridge strengthening 94 kg of steel can be replaced by a mere 4.5 kg of Carbon FRP (Meier and Kaiser 1991)]. FRP also has excellent dura bility, non electromagnetic besides, electrical neutrality. In addition, they are much flexible such that they can be made almost for any desired shape, simple to handle in the field position, occupy negligible space as compared as to the existing structur al members. Their major drawbacks as materials for rehabilitation are as follows: (1) Ultraviolet degradation of the resin. However, this can be minimized by surface coating or inclusion of some additives to the resin. (2) Weather: Weather may cause some p unctures or cracks to FRP. For example, the weather has an impact may reduce the flexural properties of GFRP by 12 to 20% in 15 years. However, some protective paint can minimize such adverse effect of weather. (3) Moisture exposure: Absorption of water ca n cause some degradation of the resin that may have an influence on some of the mechanical properties of the resin and, in turn, that of FRP. It is a function of the type of resin and the degree of cure. (4) Toxicity: Smoke that comes out during burning of resin may be toxic. However, the material usually utilized for rehabilitation is in most cases small and in the open. Therefore, the hazard from toxicity is small. (5) Flammability: Polymer matrix is very susceptible to fire. However, properly formulated resin may burn, but they do not support combustion. Currently, different types and shapes of FRP materials are commercially produced. Carbon FRP (CFRP) and Glass CFRP (GFRP), beside Aramid FRP (AFRP), are some of the well

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14 known FRP types. They are availabl e in rods, fabrics, and strands. Therefore, FRP material has been produced in one, two, and three dimensional fabrics and rods. Although the FRP material, in comparison to steel, are still expensive but due to their superior physical and chemical propertie s, there is an indispensable and keen tendency toward using FRP to rehabilitate infrastructures. As a result, the demand on FRP is rapidly increasing, especially in industrialized developed countries. 2.3 Types of FRP Compos ites and Applications 2.3.1 FRP Composite FRP made of fiber filaments embedded in the adhesive matrix. CFRP, GFRP, and AFRP are the most common FRP categories that have used in rehabilitation infrastructure. Also, few studies have been done using basalt fiber reinforced polymer (BFRP) in few countries. However, CFRP and AFRP are the most common tendons that use in North America. FRP composites are available in different shapes and size such forms of bars, multi wire strands, sheet, ropes, or cable s. Properties of the FRP composites can be varied based on the production company. It is because the mechanical characteristics are highly depended on the mechanical properties of the fiber and the matrix, the fiber volume fraction of the composite. The de gree of fiber matrix interfacial adhesion, the fiber cross section, quality, and direction within the matrix, the loading period and duration, as well as environmental situation and the process of manufacturing (ISIS 2001). Typically, there are two ways of strengthening techniques where: (1) FRP sheets are saturated on place along with the resin bonded to the surface and called wet overlaid.

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15 (2) FRP sheets are saturated and cured before place application and then used to the surface with adhesive, and thi s method is called pre cured system. 2.3.2 Types of FRP 1 AFRP The name ARMID formed from the term of AROmaticpolyAMIDe (synthetic organic fiber). AFRP has a lower modulus and lower weight than CFRP. Also, the cost of AFRP is lower than CFRP. Six d ifferent types of fibers have been used to form AF RP rods. 1. Kevlar includes four different grades (Grade 29, 49, 129, 149) 2. Twaron 3. Technora 4. Aropree 5. FiBRA 6. Rarafil The tensile strength of the fiber varies in a range of 2800 MPa 4 100 MPa and the module varies between 74 GPa 179 GPa. As shown in F igure.2.3.

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16 ( a ) ( b ) Figure 2. 3 AFRP (a) ten dons and (b), laminates 2. GFRP GFRP consists glass fibers E glass fibers applied in FRP industry than C and D glass fibers. GFRP is highly resistance to alkaline solutions but sensitive to moisture. Moreover, it is sensitive to creep rupture under sust ain stress. GFRP is highly resistance to chemicals and has a cheaper cost than CFRP. GFRP laminates, rods and strips are available in the market for various applications. Tensile strength of GFRP varies in a range of 1379 1724 MPa. As shown in figure.2.4 Figure 2. 4 GFRP size.

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17 3. CFRP FRP contains carbon fiber called as CFRP. CFRP consists with the properties of high strength, high stiffness, excellent fatigue properties, and high moisture, thermal and chemical resistance. Synthetic fibers [polyac rylonitrile (PAN)] and pitch based fibers have been widely used in CFRP industry. PAN type used in the carbon fiber composite cable (CFCC) industry. CFCC made as a single rod or a combination of a standard number of cables (Figure 2.5 a). The modulus of ca bles is about 137 GPa, which is less than the modulus of steel tendons. Pitch based fibers used to make CFRP rods. The diameter of these rods varies in the range of 3 mm to 17 mm (Figure2.4 b). The tensile strength of rods is about 1813 MPa, and the modulu s is about 147 GPa. Additionally, CFRP sheets and strips are available for several applications as shown in (Figure.2.5 b, c) (ISIS 2007). (a)

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18 ( b ) ( c ) Figure 2. 5 CFRP (a) tendo ns ( b) laminates size, and (c) sheet.

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19 2.3.3 Properties of FRP Composites materials defined as matrices of polymeric materials reinforced with fibers or another reinforcement with an observable of side ratio of length to thickness. Therefore, manufacturing techniques for material's composites (FRP) include the following; pultrusion, filament winding, lay up methods, compression molding, injection molding, resin transfer molding, and performing methods. Predominantly there are three steps in th e manufacturing of Composites Materials (FRP): (1) The elementary step is processing of constituent materials such as resin and reinforcing fibers polymer. (2) Processing of constituent materials into required forms thru dough molding compounds and fiber preforms. (3) The final step is shaping and curing processes of combined constituents into its final form. The final properties of materials components FRP are affected by previous steps. The most mainly factors influencing physical performance of the FRP matrixes composite materials are fiber direction, length, format and composition of the fibers. The mechanical characteristics of the resin matrix and the adhesion of bond or cohesion between the fibers and the matrix also are influencing the perf ormance. Moreover, the FRP is different to steel, so the mechanical characteristics of FRP vary significantly from one product to another. The factors such as volume and kind fiber and resin, fiber direction, dimension influence and quality monitoring duri ng the manufacturing, play a significant assignment in establishing the characteristics of the FRP materials. Furthermore, the mechanical characteristics of FRP are influenced by factors as the period

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20 of loading and duration and temperature beside moisture Some of the highly significant mechanical characteristics placed in the succeeding subsections. 1 Relationship between Stress and Strain There isn't relationship between the stress strain of FRP materials with plastic range and stress increasi ng linearly from the origin to the maximum point of stress. Consequently, the ultimate strain for the most of FRP materials, are higher than the yield strain of steel. Accordingly, for rehabilitation purposes FRP materials have worked as sheets bonded to t he tension surface of the beam section. In Figure 2.6 shows the relationship between stress strain for various types of FRP along with steel. Figure 2. 6 Stress strain relationship for FRP and steel

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21 2 Tensile Strength One of the most signifi cant properties of FRP materials is their high tensile strengths. They are equal to or up to about two times higher than those of prestressed steel rods and totally high compared with regular steel. While, tensile strength of FRP reinforcement is influence d not only by volume ratio, cross sectional area of fiber, in addition to tensile strength have influenced the tensile strength of FRP reinforcement but also the bond performance of fibers and matrix. Nevertheless, composites pass along their maximum tensi le strength without display any yielding of the material. The tensile strength for FRP materials Ranging from 400 700 Mpa for Glass fiber reinforced polymer (GFRP), 1000 2800 Mpa for Carbon fiber reinforced polymer (CFRP) and 1200 1700 Mpa for Aramid fiber reinforced polymer (AFRP) reinforcement (Mochizuki et al. 1993). 3. Specific Gravity The composites materials FRP light weight and have gravity ranging start from 1.5 until 2.0. In contrast, they are four time lighter than steel. Thus, significant a dvantages may be gained as lower transportation and storage costs in addition decreased handling on the job site and also installation time as compared to steel. 4 Modulus of Elasticity The modulus of elasticity of CFRP is ranging from 0.5 to a va lue twice as more as that of steel. However, the modulus of elasticity for GFRP and AFRP are lesser than steel. FRP for rehabilitation, modulus of elasticity is not as a crucial property as a principal reinforcing

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22 material. Typical values of modulus of ela sticity E for FRP materials range from 40 50 GPa for Glass fiber reinforced polymer (GFRP), 120 200 GPa for Carbon fiber reinforced polymer (CFRP) and 50 70 GPa for Aramid fiber reinforced polymer (AFRP). 5. Compressive Strength Although, The FRP composit es have high strength in tension, and are weak in compression. However, still composite material with higher tensile strength has higher compressive strength. In all cases, the compressive strength is not crucial when used as a material for repair. 6. Temperature Resistance Within the range of temperature that a structural member will experience during service that is expected to be 30 C < T < 80 C, the tensile fiber strength is not markedly concerned. In general, several composites have well to ex cellent characteristics at elevated temperatures. In any case, because the elevated temperature reduces the modulus of elasticity and strength and, moreover, causes time dependent deformation, the glass transition temperature (Tg) must be clearly above the maximum service temperature. 7 Ultraviolet Rays When FRP materials used as external reinforcement, the impact of ultraviolet (UV) rays must not be ignored. In some kinds of FRP, ultraviolet rays may generate chemical reactions in the polymeric mat rices, which can reach a degradation of their characteristics

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23 (Mufti et al. 1991). Resins can quickly deteriorate by ultraviolet rays when they are exposed to direct sunlight. In a study conducted in Japan (Ummoto 2001), where FRP rods exposed for three ye ars to a marine environment and standard atmosphere, the rods suffered some appreciable decrease in their strength. The strength reduction was 30 32% in AFRP, 1 19% in GFRP rods and 9 17% in CFRP rods. Haebele et al. (2002) evaluated the effect of UV radia tion on vinyl ester and vinyl ester matrix composite both in out of doors exposure and the laboratory. They watched, after one year of exposure to the marine environment, extended surface damage to the composite material with no significant influence on th e strength, modulus and strain to failure. On the other hand, using the laboratory apparatus with accelerating aging at the level of 4 5 times the outdoor environment, based on ene rgy comparison with the help of scanning electron microscopy. They found degradation of the matrix away from the fibers in the composite, and the presence of surface is cracking. Accordingly, they concluded that although UV affected the surface of the material it did not decrease the strength of the materials. Nevertheless, the issue can be resolved by using some specific additives, adding a little special paint on the exposed surface of the material (Saadatmanesh et al. 1994), or use a thin layer of concrete cover to the FRP surface. 8 Fatigue Many experimental rese arches of tests were carried out to estimate the fatigue life of FRP materials. The study considered various range of tensile stress and frequency (Tannous and

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24 Saadatmanesh 1998, Ukomoto 1995, Mori et al. 1995, Adimi et al 1988), impact of temperature (Ad imi et al. 1988 Nishizaki et al. 1997), and presence of moisture (Nishizaki et al. 1997, Demers 1998, Matsuo et al. 1997). The results showed that FRP composites exhibit excellent fatigue resistance. The most of the research in this regard has been on g reat performance fibers, and Aramid same graphite, which are subjected to large cycles of tensi on tension or flexural loading. In tests where the loading returned for over 3 million cycles, it was concluded that Carbon and Aramid are excellent fatigue stre ngth resistance than steel besides the fatigue strength of glass composites is smaller than steel at low stress ratio. I t was also pointed out that the fatigue life of FRP materials are very significant dependent on the applied load, stress range, specimen shape, fiber reinforcement, percent of fiber and resin, and the number of cycles. Test results also explained that behavior of moisture and increases in temperature over the normal room temperature have the reverse influence on the fatigue life of the com posite materials. 9 Ductility In addition, to structural strength, ductility is considered to be the primary safety concern to the design of plate elements. It characterized by the ability of the member to undergo excessive deflection o r rotation w hile sustaining all its strength limit. As FRP materials have no yield plateau, members reinforced or strengthened/upgraded with them are not expected to decline in the same manner as those contained steel

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25 reinforcement only. The first are expected to miss in no or reduced ductile manner. The main situation when FRP plates are bonded to the soffit of the beams to upgrade, repair or strengthen them. Bonding a plate to the tension side of the concrete beam may increase its flexural capacity, and it can drasti cally degrade the ductility of the beam and transfers it to brittle failure (Spadea et al. 1997, Al Sulaimani et al. 1994). On the contrary to this, wrapping columns with FRP sheets (Katoaka et al. 1997, Katsumata and Kobatake 1997, Masukawa et al. 1997, O kano et al. 1997, Hakamada 1997) or prefabricated composites (Xiao 1998) can profoundly improve the ductility of columns especially if they suffer from low shear capacity. However, generally speaking, when using FRP material, some special measures might b e considered reducing the possibility of catastrophic failure. Some of these are: (a) Using higher material factor of safety. (b) Consider, if necessary, a little unique measure to attain ductility such as confinement of concrete at compression zone or use some steel reinforcement to present some of the ductility. (c) Attain some attention to end anchorage (in case of beams) to restrain the relative slip between the plate and the concrete. 10. Creep and Creep Rupture Fibers such as graphite an d glass have high resistance to creep while the like is not right for most resins. Subsequently, the direction and volume of fibers have a significant affected on the creep performance. The Creep studies were conducted in Germany on GFRP

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26 composites with di fferent cross sections. These studies showed that the stress fracture decreases if the sustained loads limited to 60% of the short term strength of the specimen (Budelmann and Rostasy 1993). The short term is (48 hours ) and long term is ( 1 year ) sustai ned load on GFRP and CFRP tendons at 50% of the ultimate strength at the room temperature of 70F (21C) show little creep and the modulus beside utmost strength after the creep test do not change significantly (Anigol 1991). The short term is 48 hours st ress strain curve of FRP material is linear, but the long term one year is a little non linear due to creep. However, the creeping influence is highly dependent on the level of the continued stress and the matrix the FRP materials. According to Yamaguchi e t al. (1997), the crucial stresses due to stress rupture are 0.3, 0.47 and 0.91 for GFRP, AFRP and CFRP respectively after 50 years. For the same duration of time Ando et al. (1997) realized the critical stresses to be 66% for AFRP and 79 % for CFRP. Ewan et al. (2001) used the several conservative results reported in the research and summarized that the stress limits for a service life of 50 years are 30 % for GFRP, 45 % for AFRP and 80%, for CFRP. The similar values for 100 years are, respectively, 25% f or GFRP, 40% for AFRP and 75% for CFRP. The corresponding limits recommended by Audenaert et al. (2001) are 30% for GFRP, 40 55% for AFRP and 60 80% for CFRP.

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27 11. Durability The composites material FRP reinforcement has more resistance to corrosion than s teel. The greatest benefit of FRP over steel is resistance to chemical attack from acids, alkalis, solvents, oils, etc. In view of growing disquiet global about infrastructure deterioration and life cycle costs of structures engineering, as well as long te rm performance in aggressive environments, the use of FRP materials may already be cost useful for range of particular applications. There is a general agreement that FRP materials are superior to glass and Aramid fibers in resisting alkaline, sea water, w et and dry cycles and other chemical solutions and cr itical environmental situations (Tannous and Saadatmanesh 1998, Walton and Yeung 1986 Toutanji and El Korchi 1998, Chajes et al. 1994, Katsuki and Umoto 1995). Although the chemical and severe environ mental conditions have a few effects on CFRP materials, but the type of resin, temperature, chemical concentration, duration of chemical exposure, and axial tensile stress on the fibers influenced at degree degradation of the FRP material due to chemical a nd difficult environmental impacts (Rostasy 1997, Sen et al. 1997, Tannous and Saadatmanesh 1998, Katsuki and Umoto 1995, Porter et al. 1996, Steckel et al. 1998, Porter et al. 1997, Arockiasamy et al. 1995).

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28 2.3.4 FRP application on Rehabilitati on The application of FRP to existing structures divided into two main sections: externally bonded FRP systems in addition to near surface mounted NSM systems. The composite of FRP does not vary and typically involves one fiber type regardless of the app lication type. The types of FRP available in the market are Carbon (C), glass (G), or aramid (A) FRPs (ACI 440 2008) with carbon is the most commonly used. Recently, the construction industry has begun to apply composites as strengthening materials (Pendha ri et al., 2008). Although, the strengthening and rehabilitation of infrastructures by FRP composites attracted considerable interest (Hollaway, 2003) the first application of bonding FRP material to a metallic structure was in mechanical engineering (Shaa t et al., 2003). The mechanical characteristic of FRP composites depends on the kind and direction of carbon fiber rate of the resin material and curing conditions. Some studies focused on the influence of the adhesive materials, due to the prosperity o f composite CFRP technique that depends mainly on the efficiency of the adhesive material to transferring the load between steel and the CFRP composite. There are many factors which affected transferring the load such as surface preparation, adhesive mater ial beside thickness, the length of bonding, in addition thickness and number of CFRP laminate.

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29 Table 2.1 CFRP composite type Young`s Modulus (GPa) Tensile strength (MPa) Elongation at failure, (%) Unidi rectional pultruded Sika Carbodur strips (Bocciarelli et al., 2009) >200 >280 >1.35 High modulus unidirectional sheets (Al Shawaf et al., 2008) 640 2650 0.4 M Brace CF 130 sheets (Liu et al., 2009) 240 3800 1.55 M Brace CF 530 sheets (Liu et al., 2009) 640 2650 0.4 Sika Carbodur M 914 pultruded plates (Fam et al., 2009) 125 1914 Sika Carbodur H 514 pultruded plates (Fam et al., 2009) 313 1475 H S strips (Harries et al.,2009) 155 2790 1.8 2.4 Corrosion Effect The de grading effect of general corrosion is reflected in the decreased thickness of the plating, which in turn decreases the moment of inertia of the ship cross section and thus induces higher stress levels for the same applied bending moments. The formulation can accurately assess the degrading effects of both crack growth due to fatigue and corrosion on instantaneous and time dependent reliability. In most of the studies, corrosion is usually obtained within accelerated conditions. However, the rate of corrosi on is a critical factor to the distribution of corrosion results, corrosion cracks, and therefore bond behavior

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30 (Tepfers 1979). As a result, laboratory samples usually develop extra cracks and less bonding strength relative to actual structural members at the similarly level of corrosion. Although accelerated corrosion specimens will not truly realize actual members in the site, they still provide significant development and benchmark data for further studies. Corrosion of the steel member in the field perh aps takes decades to cause damage. Therefore, for research purposes, corrosion in the laboratory is often accelerated. The 2 (FIB 10, 2000). At this low rate of corrosion tests in the laboratory, environment would take years. Therefore, researchers have accelerated the corrosion process by a technique based on the fact that the corrosion process is activated by salts solution and accelerated by electrical polarization of the steel m ember. The specimen is connected to the positive terminal of an external energy supply so that a positive electrical potential is applied to the steel. Researcher has used external steel bar connected to the negative end of the potential supply to operate as a cathode during the corrosion process. Power supplies can impress either a constant voltage or a constant current. A constant current system was used by (Al Musallam et al. 1996) to accelerate corrosion of reinforcing steel in the concrete slab. A cons tant current of (2A) Ampere was applied to the steel using a direct current rectifier. When the constant impressed current technique used, the mass loss of the specimen is estimated using 2.5 Fourier Transformation Infrared Spectroscopy (FTIR) Infrared spectroscopy records changes in power of vibration and rotation effected by

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31 whole spect rum of infrared is arbitrary distributed into near, mid and far region as shown in Table.2.2. Table 2.2 Sections of infrared emission and corresponding energy transitions Region 1 Energy transition Near 0,78 2,5 12800 4000 Overtone or harmo nic vibrations Mid 2,5 5 0 4000 200 Rotational vibrational Far 50 1000 200 10 Rotational

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32 2.6 Summary and Conclusion Based on the Author knowledge, it is very difficult to draw a conclusion fr om the literature reviews. Through the mentioned studies, it can be said that almost all of previous research studies on tension and compression were conducted in the context of flexural member applications. There were no studies in the direct applications to steel member structures with CFRP sheet under galvanic corrosion damage. Hence, the present study is focused on a new method of applying direct environment corrosion to specimens. This new method will provide new results on the effect of CFRP character istics with steel members affected by corrosion. With all these studies conducted, very minimum research has focused on the performance of CFRP sheet at different type of damage. The research presented in the following chapters is one step further in deve loping the FRP emerging technology and ultimately developing a design method or recommendations for the FRP strengthening applications under damage.

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33 3. Behavior of Corrosion for Interface test Specimen 3.1 Fabrication and Specimen Design 3.1.1 Genera l Overview This chapter presents the dimensions and characteristics of the materials used in this study including steel substrate, CFRP, and adhesive materials. A total of 35 double lap joint specimens ware prepared and exposed to an aggressive service en vironment in conjunction with an electrical potential method accelerating corrosion damage. Six test categories are planned at a typical exposure interval of 12 hours, including five specimens per category. The degree of corrosion is measured. Upon complet ion of corrosion processes, all specimens are monotonically loaded until failure occurs to measure their residual capacity. A relationship between the level of galvanic corrosion and the failure characteristics of steel composite interface is established. Below is a summary of these test schemes and corresponding material properties 3.1.2 Materials Table 3. 1 summarizes the details of materials; include the tensile strength (MPa), tensile Structural st eel includes specified yield strength of 413 MPa and an elastic modulus of 200GPa. The unidirectional CFRP sheet s

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34 used ha ve a nominal tensile strength ( f fu ) of 3,800 MPa with modulus ( E f ) of 227 GPa, based on an equivalent thickness of 0.165 mm (BASF 2007) These characteristics were comparable to those measured in a coupon test: f fu = 3,590 MPa and E f = 246GPa (Kim and Brunell 2011). The kind of adhesive was employed to bond the CFRP to a steel substrate was epoxy. The epoxy adhesive used as a two part mix ture consisting of a hardener and resin to be combined at a ratio of 1:3 by weight, respectively. It has a tensile strength of 54 MPa with corresponding modulus of 3 GPa, including a ruptured strain of 3.5% (MBrace 2003). 3.1.3 Preparation Interface test specimens were prepared using two steel strips (100 mm long 37 mm wide 3 mm thick, each) or (4*1.5*0.128) in bonded with one layer of CFRP sheet (100 mm long 37 mm wide 0.165 mm thick, each) or (4*1.5*0.0065) in per side, as shown in Fig ure 3.1 The surface of the steel was roughened using an electric grinder to improve the bond along the adhesive substrate interface. The bonding agents were mixed according to the as shown in Fig u re 3.2 followed by impregnating the CFRP for permanent bonding as shown in Fig ure 3. 3 The element level test specimens were cured at room temperature for two weeks. Six categories were designed to examine the behavior of the CFRP steel interface bonded w ith epoxy adhesives. Strain gages were affixed to the CFRP at a typical spacing of 25 mm. The cured specimens were loaded in monotonic tension until interfacial failure occurred

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35 3.1.4 Test Specimen A total of 35 specimens made of steel strips and CFRP w ere prepared and tested. The specimens were corroded by using the initiation of corrosion accelerated application of electrical potential. These specimens were exposed to these environmental conditions for different durations, from 12 Hr to 72 Hr as shown in Figure 3.4. In addition five specimens for the control case this is mean no corrosion in these specimens. There is some concern regarding possible galvanic corrosion when CFRP and steel strips were bonded together. Specimens were placed in a container a nd partially immersed in a 3.5% salt by weight solution. Thus, the corrosion rate was considered. After the exposure time, the specimens were removed from corrosion cell. A dimensional verification was carried out and weights as shown in Figure 3.5. Figur e 3.6 show the different of corrosion between before and after the corrosion happened. MTS machine was used to the expense of strength to specimens and also in order to calculate the tensile strength of all specimens under study as shown in Figure 3.7. 3.1 .5 Corrosion Exposure The electrochemical cell device has used to accelerate corrosion. It was used to separate the reactants in a chemical reaction so that the electrons transferred from one reactant to via an external power circuit. In the galvanic corr osion cell, the chemical reaction happens

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36 as the reaction proceeds spontaneously. Because the current flow of the external circuit a net result is the conversion of the capacity of a chemical reaction into electrical capacity. In this study, current can be forced to flow through the cell by using external power source direct current (DC) power supply (2 A) as shown in Figure.3.4 (a,b) This process, estimate of the corrosion rate of the material in a solution, and galvanic corrosion rate of two materials coupled together. During this test, the potential (v), and the current were monitored to use two methods. The mass loss method (mm/y) and Faraday law method (mm/y) were used to calculate the corrosion rate. In addition, the weight and the surface area were calculated for all the specimens. 3.2 Corrosion Testing 3.2.1 Mass Loss Method 3.2.1.1 Determination of Surface Area of the Specimens The length, wide and the thickness of specimens and the surface areas of the specimens were calculated. 3.2.1.2 Weig h ting the Specimens before and after Corrosion All the weighting of the specimens before and after corrosion was carried out using Shimadzu balance as shown in Figure (3.5).

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37 3.2.1.3 D etermination of Corrosion Rate The weighted specimens were suspe nded by means of test solutions, and after period (12 H r to 72 Hr) of immersion, the specimens were taken out, washed in water, dried, and weigh t ed. From the change in weights of the specimens, corrosion rates were calculated using the following relationsh ip ( V. Johnsirani els.., 2012 ) : Where: W = mass loss in milligrams, D = density of specimen g/cm 3 A = area of specimen in cm 2 and T = exposure time in hours. 3.2.2 The basis of a rate expression fo : Where: i = the current density, W = mass loss in milligrams, T = exposure time in hours, n the number of electrons transferred, F is the Faraday constant (96500 Cmol 1 ) and D = density of specimen g/cm 3 3 2.3 Fourier Transformed Infrared Spectroscopy ( FTIR ) Method Infrared spectroscopy is a popularly used technique that for many years has been an imperative tool for examining chemical processes and str ucture. The compound of infrared

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38 spectroscopy with the principles of observation has presented advances in surface analysis reasonable. Specific IR reflectance systems may be divided into the spaces of specular reflectance, diffuse reflectance, and interna l reflectance. In preparing pastilles for FTIR spectroscopy measurements specimens of corrosion, products were separated from all specimens. CFRP sheet specimens were cut out in dimensions of 20 30 mm. FTIR absorption spectra were recorded at room temper ature with Perkin Elmer spectrometer, model 2000. Prepared specimens were photographed in mid (4000 400 cm 1 ) infrared range. Operation of the FTIR was controlled by IRDM program, which at the same time enables the processing of the spectra as shown in F igure 3.8. Also, all specimens were characterized by IR spectroscopy (appendix C) 3.3 Mechanical Testing 3.3 .1 Capacity of L oading An interface joint tension test was conducted to study the behavior of CFRP steel interface all specimens were pos itioned to an MTS machine for mechanical testing, as shown in Figure 3.7(b). Table3.2 provides the details of the test specimens, including the type of different durations from 12 Hr to 72 Hr, In addition five specimens for control. A monotonic tension lo ad was used to the samples at a rate of 0.5 mm/min until failure happened Figure 3.7(c). Load and displacement have been a record by a built in load cell and the stroke of the loading head, respectively. The failure mode of the adhesive epoxy coupons and t he CFRP sheets are shown in Figure 3.7.

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39 3.3 .2 Strain G age R eading Strain gages (gage length = 5 mm) were fixed on the CFRP sheet at 25 mm on center to measure the improvement of CFRP debonding, as shown in (Figure. 3.7a). After the curing for a week the double lap test specimens were loaded in tension at a rate of 0.5 mm/min to failure occurred. The performance of CFRP sheet under tension load was consistent over the ratio of corrosion. All data recorded by a data acquisition system. The results su mmarized in the next section. From the results and literature review the corrosion ratio has effect on the CFRP tension capacity. 3. 4 Experimental Results 3. 4 .1 Analysis of Corrosion The corrosion rate was monitored using in situ electrochemical methods such mass loss method and Fourier Transformed Infrared Spectroscopy ( FTIR) method 3. 4 1.1 Mass Loss Method This method was used to obtain the corrosion rates from the change of surface area and weight of specimens as shown in Table3.2. It observed that little change in the surface area as shown in Figure 3.9, but there few change in the weight as shown in Figure 3.10. The

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40 corrosion rates of Interface test specimens obtained by mass loss method given in Table 3.4. The corrosi on rate by mass loss method was slightly increasing Figure 3.13. 3.4.1.2 This method was used to obtain the corrosion rates from current density and potential voltage of specimens during the corrosion cell as shown in Table 3.3 It observed that both potential and current density decreased as shown Figure 3.11 and Figure 3.12. The method was slightly increasing Figure 3.14. In addition, which indicates that the corrosion rate both mass loss 3.4. 1.3 Fourier Transformed Infrared Spectroscopy (FTIR) Testing The sp ectra were recorded as single channel spectra and afterward converted to absorbance spectra. The FTIR absorbance spectra of the corroded specimens shown in Figure 3.16 and Figure 3.17. The examining corrosion from a short period of exposure to the long per iod of exposure was essentially the same as examining corrosion occurring in all specimens; each spectrum was a snapshot of corrosion occurring increased. Figure 3.16 (a) the OH stretching frequency seems at 3408 cm 1 .The C= O stretching frequency seems a t 17 1 cm 1 An asymmetrical C O C stretching frequency of aryl alkyl ethers occurs at 1224 cm 1 The group at 1087 cm 1 corresponds to the symmetrical C O C stretching of alkyl aryl ether. The FTIR spectrum of the preservative film formed on the

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41 surface of the CFRP after immersed in the solution. After curing days do not indications of corrosion of the examined CFRP, were noticed in any of the control specimens. However after expose all specimens to chemical cell, corrosion was noticed in the all of specime ns as shown in Figure 3.16(a g).The C=O stretching frequency has reduced from 1715 cm 1 to 1613 cm 1 An asymmetrical C O C stretching frequency of alkyl aryl ether (1224 cm 1 ) disappeared. A Symmetrical C O C stretching of alkyl aryl ether (1087 cm 1 ) di sappeared. Figure 3.17 (a,b) shows the difference between all of the specimens. 3. 4 .2 Load Displacement Response The interfacial strength of the test specimens summarized in Table 3.5. The control specimens (the G series) showed an average capacity of 28 .14 kN. While the ones with exposure after 72 Hr (the X series) exhibited an 85% lower capacity than the control specimens, on average as shown in Figure3.1 8 Figure 3.1 9 shows the load displacement response of the specimens. All series exhibited a linear response until an abrupt load drop was associated due to bond failure Figure. 3.1 9 (a). The stiffness of the respective specimens was more or less similar to each other, while the strength was slightly different. That, explained by the fact that the amount of epoxy was not the same because of the experimental randomness to a certain extent. The specimens subjected to the exposure corrosion demonstrated similar behavior Figure. 3.1 9 (b) to (g), while a local load drop was noticed in some cases. Such an obser vation illustrates that the interface was partially damaged due to a period of exposure. A comparison of load displacement for test categories of different ratio of corrosion was shown in Figure. 3. 20

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42 3.4.3 Strain Gage Response The measured load strai n behavior is given in Figure 3. 21 (a) (g). The increment of CFRP strains was negligible until a normalized load of 29.94 kN was accomplished Figure.3. 21 (a). The normalized load is defined as (Pu) ultimate loads of the interface (Gage1, 4) test specimen, r espectively. CFRP debonding was noticed at 18 kN where a sudden increase in strain was recorded and rapidly propagated along the interface (Gage2, 3), leading to the failure of the specimen Figure.3. 21 (a). Development of CFRP strain profiles is summarized in Figure 3.2 2 Control specimen revealed a typical CFRP strain history with a gradual increase in strain at joint (mid joint of the specimen), followed by rapid CFRP debonding, as shown in Figure. 3.2 2 (a). The specimen with 72hr exposure illustrated low er strain development in comparison to control specimen with no corrosion and some residual strains were recorded when the beam failed Figure.3.2 2 (g). 3.4.4 Failure Mode of Interface Test Specimen Figure 3.2 3 shows the failure mode of the interface test The control specimens with no corrosion display typical CFRP debonding failure Figure.3.2 3 (a) and the spotless failure surface indicates adhesion failure has dominated the CFRP steel interface rather than cohesion failure. In addition, the specimens w ith corrosion after 72hr have shown CFRP debonding failure Figure. 3.2 3 (b).

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43 3.5 Summary and Conclusion This chapter has discussed the residual behavior of CFRP sheet embedded in a steel substrate when subjected to elevated corrosion exposure from 12 H r to 72 H r One type of adhesives was used to bond the strips. Test specimens were conditioned in the predefined corrosion environment until 72 hours and mechanically loaded to failure. Interfacial strength between the CFRP and steel was measured and corresp onding failure mode was studied. These technical results are part of an ongoing research program examining the performance of CFRP strengthening system for steel structures with focus on material and structure level investigations. Some preliminary c onclu sions are drawn as follows: According to the statistical analysis, the variation of steel strips strength in corrosion ratio was influenced by period of exposure from 12 H r to 72 H r. The capacity of the CFRP steel interface was, however, affected by corro sion exposure within this boundary. The interfacial capacity of the control specimen was higher than the high ratio of corrosion, even though the high ratio of corrosion showed a consistent capacity over the first two period of exposure to corrosion incre ase

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44 Table 3.1 Material properties from manufacturer Steel CFRP Epoxy adhesive Tensile strength (MPa) 413 3800 54 Tensile modulus (GPa) 200 227 3 Ultimate strain 0.002 0.0167 0.035 0.3 0.27 0.4 Table 3.2 Test matrix ID Type of Environmental Effect Surface Area ( cm 2 ) The loss of mass ( g ) Individual Average STDEV Initial After exposure Individual Average STDEV G1 338.6 338.6 0.0 202.4 202.4 0 0.0 0.0 G2 0 Hr/ELC 338.6 198.7 198.7 0 G3 No corrosion 33 8.6 200.8 200.8 0 G4 338.6 203.2 203.2 0 G5 338.6 201.7 201.7 0 O1 334.8 333.8 3.7 195.6 194.8 0.8 2.5 3.4 O2 337.1 197.4 197.3 0.1 O3 12 Hr/ELC 336.9 199.9 199.2 0.7 O4 328.4 192.7 184.4 8.3 O5 331.9 195.4 192.9 2.5 A1 336.8 333.5 3.1 199.4 198.2 1.2 5.7 6.8 A2 330.1 196.1 187.4 8.7 A3 24 Hr/ELC 330.6 197.2 180.7 16.5 A4 334.1 193.8 192.5 1.3 A5 335.9 198 197 1 V1 325.9 331.8 4.0 198.1 177.8 20.3 8.7 8.1 V2 336.3 199.7 199.1 0.6 V3 36 Hr/ELC 330.2 193.7 183.6 10.1 V4 332.2 198.9 187.7 11.2 V5 334.4 197.4 196.1 1.3 W1 327.6 330.4 3.8 202.6 193.7 8.9 13.2 6.7 W2 334.6 203.3 187 16.3 W3 48 Hr/ELC 334.6 206.9 184.4 22.5 W4 327.6 202.1 197 5.1 W5 327.6 209 196 13 N1 332.1 327.9 14.3 197.2 181.4 15.8 17.7 13.0 N2 302.6 197 158.5 38.5 N3 60 Hr/ELC 333.7 203.5 188 15.5 N4 335.3 20 2.4 186 16.4 N5 335.9 198.7 196.4 2.3 X1 307.3 275.5 55.2 198.7 169.1 29.6 34.0 20.8 X2 216.2 197.3 136.9 60.4 X3 72 Hr/ELC 215.6 194.6 144.1 50.5 X4 308.0 198.3 185 13.3 X5 330.3 196.3 180.1 16.2 ELC Electrochemical Cell

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45 Table 3.3 Test specimens for electrical ID Type of Environmental Effect Potential ( V) Current density (A/cm2) Individual Average STDEV Individual Average STDEV G1 0 Hr/No corrosion 0.0000 0.0000 0.0000 0.0E+00 0.0E+ 00 0.0E+0 0 G2 0.0000 0.0E+00 G3 0.0000 0.0E+00 G4 0.0000 0.0E+00 G5 0.0000 0.0E+00 O1 12 Hr/ELC 0.8900 0.9200 0.3032 1.6E 06 1.6E 06 5.1E 07 O2 0.6400 9.5E 07 O3 1.2300 1.6E 06 O4 1.2300 ` 2. 4E 06 O5 0.6100 1.4E 06 A1 24 Hr/ELC 0.2050 0.2872 0.0804 3.6E 07 4.7E 07 1.2E 07 A2 0.2420 3.9E 07 A3 0.2420 3.9E 07 A4 0.3650 5.9E 07 A5 0.3820 6.1E 07 V1 36 Hr/ELC 0.1280 0.1348 0.0170 2.3E 07 1.9E 07 9.1E 08 V2 0.1290 1.7E 07 V3 0.1240 4.2E 08 V4 0.1650 2.8E 07 V5 0.1280 2.2E 07 W1 48 Hr/ELC 0.0840 0.1038 0.0455 1.4E 07 1.1E 07 9.7E 08 W2 0.1500 2.5E 07 W3 0.1330 1.6E 08 W4 0.1170 9 .4E 08 W5 0.0350 2.8E 08 N1 60 Hr/ELC 0.0091 0.0075 0.0016 3.9E 09 3.1E 09 1.8E 09 N2 0.0074 1.9E 09 N3 0.0065 4.2E 09 N4 0.0054 6.8E 10 N5 0.0089 5.0E 09 X1 72 Hr/ELC 0.0068 0.0047 0.0013 3.7E 09 3.9 E 09 4.2E 09 X2 0.0045 3.1E 09 X3 0.0048 1.1E 08 X4 0.0035 4.6E 10 X5 0.0038 1.4E 09

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46 Table 3.4 Corrosion rate by mass loss and Faraday law ID Type of Environmental Effect Corrosion rate by mass loss( m m/y ) Corrosion rate by Faraday law( mm/y ) Individual Average STDEV Individual Average STDEV G1 0 Hr/No corrosion 0.0 0.0 0.0 0.00 0.0 0.0 G2 0.0 0.00 G3 0.0 0.00 G4 0.0 0.00 G5 0.0 0.00 O1 12 Hr/ ELC 2.2 7.0 9.5 2.05 8.1 13.0 O2 0.3 0.15 O3 1.9 1.79 O4 23.4 31.10 O5 7.0 5.50 A1 24 Hr/ELC 1.7 8.0 9.6 1.37 7.3 8.1 A2 12.2 10.61 A3 23.1 20.20 A4 1.8 2.43 A5 1.4 1.92 V1 3 6 Hr/ELC 19.3 8.2 7.7 22.24 8.2 9.9 V2 0.6 0.48 V3 9.5 1.99 V4 10.4 14.99 V5 1.2 1.33 W1 48 Hr/ELC 6.3 9.2 4.6 7.97 8.4 10.3 W2 11.3 26.25 W3 15.6 2.27 W4 3.6 3.04 W5 9.2 2.27 N1 60 Hr/ELC 8.8 10.3 8.1 48.94 10.0 21.7 N2 23.6 0.57 N3 8.6 0.52 N4 9.1 0.09 N5 1.3 0.09 X1 72 Hr/ELC 14.9 21.7 16.9 10.32 16.8 21.4 X2 43.2 17.81 X3 36.2 52.95 X4 6.7 0.58 X5 7.6 2.12

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47 Table 3.5 Test results of specimens ID Type of Environmental Effect Ultimate load (kN) Individual Average STDEV G1 27.8 28.9 4.1 G2 22.6 G3 0 Hr/No corrosion 34.0 G4 30.4 G5 29.4 O1 22.7 23.2 2.5 O2 23.8 O3 12 Hr/ELC 23.0 O4 19.8 O5 26.8 A1 23.2 21.2 4.5 A2 21.7 A3 24 Hr/ELC 20.2 A4 26.7 A5 14.5 V1 27.1 22.6 2.8 V2 21.4 V3 36 Hr/ELC 19.9 V4 21.5 V5 23.0 W1 22.7 2 0.6 3.5 W2 15.0 W3 48 Hr/ELC 23.2 W4 22.7 W5 19.5 N1 17.4 15.9 2.8 N2 19.7 N3 60 Hr/ELC 16.0 N4 12.9 N5 13.6 X1 4.9 6.4 2.9 X2 10.8 X3 72 Hr/ELC 5.2 X4 7.7 X5 3.5

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48 Figure 3.1 Substrate preparation Figure 3.2 Preparation of a specimen before bonding

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49 ( a ) ( b ) ( c ) ( d ) Figure 3.3 Interface test specimens: ( a ) mixing an epoxy adhesive ; ( b ) mark adhesive place ; ( c) epoxy bonding ; ( d ) after curing ( a )

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50 ( b ) Figure 3. 4 Setup for accelerated corrosion testing :(a) schematic ; (b) test pictu re ( a ) ( b ) Figure 3.5 Measuring weight of specimen: (a) before corrosion; (b) after corrosion

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51 ( a) ( b ) Figure 3.6 Comparison of specimens: (a) before corrosion ;(b) after the corrosion ( a) ( b ) (c) Figure 3.7 Tension test: (a) strain gages ;( b) stra in monitoring; (c) displacement monitoring Strain gage

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52 Figure 3.8 FTIR machine for chemical investigations Figure 3.9 Va riation of current surface area with time 0 100 200 300 400 0 12 24 36 48 60 72 Surface area ( cm 2 ) Time (Hr) Individual Average STDEV

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53 Figure 3.10 Variation of mass loss with time Figure 3. 11 Variation of potential 0 10 20 30 40 50 60 70 0 12 24 36 48 60 72 The loss of mass ( g ) Time (Hr) Individual Average STDEV 0 0.3 0.6 0.9 1.2 1.5 0 12 24 36 48 60 72 Potential ( V) Time ( Hr ) Individual Average STDEV

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54 Figure 3.1 2 Variation of current density with time Figure 3. 1 3 Corrosion Rate obtained by the L oss of M ass M ethod 0 0.3 0.6 0.9 1.2 1.5 0 12 24 36 48 60 72 Current density ( A/cm 2 ) Time ( Hr ) Individual Average STDEV 0 10 20 30 40 50 60 0 12 24 36 48 60 72 Corrosion rate (mm/y) Time (Hr) Individual Average STDEV

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55 F igure 3.1 4 Figure 3.1 5 0 10 20 30 40 50 60 0 12 24 36 48 60 72 Corrosion rate (mm/y) Time (Hr) Individual Average STDEV 0 10 20 30 40 50 60 0 12 24 36 48 60 72 Corrosion rate (mm/y) Time (Hr) Averagemass loss method AverageFaraday law

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56 (a) ( b ) ( c ) -0.10 0.00 0.10 0.20 0.30 500 1000 1500 2000 2500 3000 3500 4000 Absorbance Wavenumber,cm 1 -0.10 0.00 0.10 0.20 0.30 500 1000 1500 2000 2500 3000 3500 4000 Absorbance Wavenumber,cm 1 -0.10 0.00 0.10 0.20 0.30 500 1000 1500 2000 2500 3000 3500 4000 Absorbance Wavenumber,cm 1

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57 ( d ) ( e ) ( f ) -0.10 0.00 0.10 0.20 0.30 500 1000 1500 2000 2500 3000 3500 4000 Absorbance Wavenumber,cm 1 -0.10 0.00 0.10 0.20 0.30 500 1000 1500 2000 2500 3000 3500 4000 Absorbance Wavenumber,cm 1 -0.10 0.00 0.10 0.20 0.30 500 1000 1500 2000 2500 3000 3500 4000 Absorbance Wavenumber,cm 1

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58 ( g ) Figure 3. 16 Test specimens For FTIR: (a) No corrosion; (b) After 12 Hr ; (c) at 24 Hr ; (d) at 36 Hr ; (e) at 48 Hr ; (f) at 60 Hr ; (g) at 72 Hr -0.10 0.00 0.10 0.20 0.30 500 1000 1500 2000 2500 3000 3500 4000 Absorbance Wavenumber,cm 1

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59 ( a ) ( b ) Figure 3. 17 Comparison of FTIR for all specimens: (a) 12 Hr, 24Hr, and 36Hr with control specimen; (b) 48 Hr, 60Hr, and 72Hr with control specimen. -0.10 0.00 0.10 0.20 0.30 500 1000 1500 2000 2500 3000 3500 4000 Absorbance Wavenumber,cm 1 0Hr 12Hr 24Hr 36Hr -0.10 0.00 0.10 0.20 0.30 500 1000 1500 2000 2500 3000 3500 4000 Absorbance Wavenumber,cm 1 0Hr 48Hr 60Hr 72Hr

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60 Figure 3.1 8 Test results of specimens 0 10 20 30 40 0 12 24 36 48 60 72 Ultimate load (kN) Time (Hr) Individual Average STDEV

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61 ( a ) ( b ) 0 10 20 30 40 0 1 2 3 4 Load (kN) Displacement (mm) G1 G2 G3 G4 G5 0 5 10 15 20 25 30 35 40 0 1 2 3 4 Load (kN) Displacement (mm) O1 O2 O3 O4 O5

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62 ( c ) ( d ) 0 5 10 15 20 25 30 35 0 0.5 1 1.5 2 2.5 3 3.5 Load (KN) Displacement (mm) A1 A2 A3 A4 A5 0 10 20 30 40 0 1 2 3 4 Load (KN) Displacement (mm) V1 V2 V3 V4 V5

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63 ( e ) ( f ) 0 10 20 30 40 0 1 2 3 4 Load (kN) Displacement (mm) W1 W2 W3 W4 W5 0 10 20 30 40 0 1 2 3 4 Load (kN) Displacement (mm) N1 N2 N3 N4 N5

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64 ( g ) Figure 3.1 9 Load displacement of specimens bonded with epoxy: (a) at 0 Hr ; (b) at 12 Hr ; (c) at 24 Hr ; (d) at 36 Hr ; (e) at 48 Hr ; (f) at 60 Hr ; (g) at 72 Hr Figure 3. 20 Comparison of load displacement for all specimens 0 10 20 30 40 0 1 2 3 4 Load (kN) Displacement (mm) X1 X2 X3 X4 X5 0 10 20 30 40 0 1 2 3 4 Load (kN) Displacement (mm) 0 Hr 12 Hr 24 Hr 36 Hr 48 Hr 60 Hr 72 Hr

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65 ( a ) ( b ) 0 10 20 30 40 0 0.003 0.006 0.009 0.012 Load (KN) Strain #1 #2 #3 #4 0 10 20 30 40 0 0.003 0.006 0.009 0.012 Load (kN) Strain #1 #2 #3 #4

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66 ( c ) ( d ) 0 10 20 30 40 0 0.003 0.006 0.009 0.012 Load (kN) Strain #1 #2 #3 #4 0 10 20 30 40 0 0.003 0.006 0.009 0.012 Load (kN) Strain #1 #2 #3 #4

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67 ( e ) ( f ) 0 10 20 30 40 0 0.003 0.006 0.009 0.012 Load (kN) Strain #1 #2 #3 #4 0 10 20 30 40 0 0.003 0.006 0.009 0.012 Load (kN) Strain #1 #2 #3 #4

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68 ( g ) Figure 3. 21 Load strain behavior of specimence: (a) No corrosion: strain gages 1 4 ; ( b) After 12 Hr : strain gages 1 4 ; (c) at 24 Hr : strain gages 1 4 ; (d) at 36 Hr : strain gages 1 4 ; (e) at 48 Hr : strain gages 1 4 ; (f) at 60 Hr : strain gages 1 4 ; (g) at 72 Hr : strain gages 1 4 0 10 20 30 40 0 0.003 0.006 0.009 0.012 Load (kN) Strain #1 #2 #3 #4

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69 ( a ) ( b ) 0 0.003 0.006 0.009 0.012 -50 -25 0 25 50 Strain Distance from midspan (mm) 25%Pu 50%Pu 75%Pu 100%Pu 0 0.003 0.006 0.009 0.012 -50 -25 0 25 50 Strain Distance from midspan (mm) 25%Pu 50%Pu 75%Pu 100%Pu

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70 ( c ) ( d ) 0 0.003 0.006 0.009 0.012 -50 -25 0 25 50 Strain Distance from midspan (mm) 25%Pu 50%Pu 75%Pu 100%Pu 0 0.003 0.006 0.009 0.012 -50 -25 0 25 50 Strain Distance from midspan (mm) 25%Pu 50%Pu 75%Pu 100%Pu

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71 ( e ) ( f ) 0 0.003 0.006 0.009 0.012 -50 -25 0 25 50 Strain Distance from midspan (mm) 25%Pu 50%Pu 75%Pu 100%Pu 0 0.003 0.006 0.009 0.012 -50 -25 0 25 50 Strain Distance from midspan (mm) 25%Pu 50%Pu 75%Pu 100%Pu

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72 Figure 3.2 2 Load strain behavior of specimence: (a) No corrosion: strain gages 1 4 ; (b) After 12 Hr : strain gages 1 4 ; (c) at 24 Hr : strain gages 1 4 ; (d) at 36 Hr : strain gages 1 4 ; (e) at 48 Hr : strain gages 1 4 ; (f) at 60 Hr : strain gages 1 4 ; (g) at 72 Hr : strain gages 1 4 0 0.003 0.006 0.009 0.012 -50 -25 0 25 50 Strain Distance from midspan (mm) 25%Pu 50%Pu 75%Pu 100%Pu

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73 ( a ) ( b ) Figure. 3.23 Failure mode of interface test specimen: (a) CFRP debonding; (b) CFRP slip. CFRP debonding CFRP slip

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74 4. Behavior of Corrosion for Beam Test in Flexure 4. 1 Fabrication and Specimen Design 4 .1.1 General Overview This chapter presents the dimensions and characteristics of the materials used in this study including beam steel, CFRP, and adhesive materials. A total of 21 beam steel specimens ware prepared and exposed to an aggressive service environment in conjunction with an electrical potential method accelerating corrosion damage. Six test categories planned at a typical exposure interval of 12 hours, including five specimens per category. The degree of cor rosion is measured. Upon completion of corrosion processes, all specimens are monotonically loaded until failure occurs to measure their residual capacity. The relationship between the level of galvanic corrosion and the failure characteristics of beam ste el is established. Below is a summary of these test schemes and corresponding material properties. 4 .1.2 Materials and Preparation The steel beams used were W100*19 (W4* 13 in the US designation) with a length of 1000 mm. A total of 21 beams tested as shown in Figure4.1 and Table 4. 1 (a, b) The beams had notch depth to represent a stage of fatigue crack propagation (i.e., initial damage before repair work was conducted): 30mm (30 mm from tension flange to web) using a blade saw

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75 Figure.4.2 (a, d). The su rface of the beams prepared, and the bonded CFRP sheets were cured as in the case of the interface test specimens. The tension flange of all repaired beams was grit blasted as Figure.4. 2(b) and cleansed with an air compressor and acetone as shown in Figur e.4.2 (c). Although surface preparation commonly accepted for such a bond critical application of CFRP to improve the bond between the CFRP and substrate (Shaat and Fam 2008), specific requirements have not been developed yet. All beams were repaired using one layer of CFRP sheet (100 mm wide 0.0165 mm thick *7 00 mm long) as shown in Figure.4.3. The CFRP was bonded to the tensile soffit of the notched beams with an epoxy adhesive (t = 1.2 mm on average) as shown in Figure4.4. The repaired beams were cure d for a minimum of S even days at room temperature before a load test was conducted. Repair of the damaged beams having the same configuration as Beam CR00 was conducted with one layer of CFRP sheet. The longitudinal CFRP were designed to reduce peeling str esses at the ends of the CFRP (ACI 2008). As shown in Figure.4.1 a ll test beams were simply supported with a span length of 1000 mm and monotonically loaded in three point bending until failure occurred. Vertical stiffeners (90 mm*50 mm* 20 mm steel sectio n) were clumped to web in both sides to preclude the local and flexural torsional buckling of the beams. Instrumentation involved a load cell and a linear potentiometer at midspan with two displacement type strain transducers (so called PI gages) with a ga uge length of 100 mm. Strain gages were glued along the longitudinal CFRP to monitor debonding behavior. A data acquisition system recorded all data.

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76 4 .1. 3 Test Specimen A total of 21 specimens made of steel strips and CFRP were prepared and tested. Sp ecimens were placed in a container and partially immersed in a 3.5% salt by weight solution as shown in Figure4.5 (a,b) The specimens were corroded by using the initiation of corrosion accelerated application of electrical potential. These specimens were exposed to these environmental conditions for different durations, from 12 Hr to 72 Hr. In addition three specimens for the control case this is mean no corrosion in these specimens. There is some concern regarding possible galvanic corrosion when CFRP and steel strips are bonded together. Thus, the corrosion rate was considered. After the exposure time, the specimens were removed from corrosion cell. A dimensional verification was carried out and weights. The flexural behavior at midspan of the test beams was measured using a load cell, a linear potentiometer, and two displacement type strain transducers (so called PI gages) with a gauge length of 100 mm. Strain gauges were bonded to the CFRP to study debonding propagation. All data were recorded by a data acquisition system as shown in Figure 4.3. 4 .1. 4 Corrosion Exposure The electrochemical cell device has used to accelerate corrosion. It was used to separate the reactants in a chemical reaction so that the electrons transferred from one reactant to via an external power circuit. In the galvanic corrosion cell, the chemical reaction happens as the reaction proceeds spontaneously. Because the current flow of the external circuit a net result is the conversion of the capacity of a chemical reaction into el ectrical capacity.

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77 In this study, current can be forced to flow through the cell by using external power source direct current (DC) power supply (2 A) as shown in Figure4.5 (b) This process, estimate of the corrosion rate of the material in a solution, a nd galvanic corrosion rate of two materials coupled together. During this test, the potential (v), and the current were monitored to use two methods. The mass loss method (mm/y) and Faraday law method (mm/y) were used to calculate the corrosion rate. I n addition, the weight and the surface area were calculated for all the specimens. 4 .2 Corrosion Testing 4 .2.1 Mass Loss Method 4 .2.1.1 Determination of Surface Area of the Specimens The length, wide and the thickness of specimens and the surface area s of the specimens were calculated as shown in Figure (4. 6 ) 4.2.1.2 Weigh t ing the Specimens before and after Corrosion All the weighting of the specimens before and after corrosion was carried out using Shimadzu balance as shown in Figure (4.7).In additi on, all specimens were compared with control beams to observe the difference between all specimens after and before the corrosion occurs as shown in Figure 4.8 (a g)

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78 4 .2.1.3 D etermination of Corrosion Rate The weighted specimens were suspended by means of test solutions, and after period (12 H r to 72 Hr) of immersion, the specimens were taken out, washed in water, dried, and weighed. From the change in weights of the specimens, corrosion rates were calculated using the following relationship ( V. Johnsira ni els.., 2012 ) : Where: W = mass loss in milligrams, D = density of specimen g/cm 3 A = area of specimen in cm 2 and T = exposure time in hours. 4 .2.2 Fa : Where: i = current density, W = mass loss in milligrams, T = exposure time in hours, n the number of electrons trans ferred, F is the Faraday constant (96500 Cmol 1 ) and D = density of specimen g/cm 3 4 2.3 Fourier Transformed Infrared Spectroscopy ( FTIR ) Method Infrared spectroscopy is a popularly used technique that for many years has been an imperative tool for exa mining chemical processes and structure. The compound of infrared

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79 spectroscopy with the principles of observation has presented advances in surface analysis reasonable. Specific IR reflectance systems may be divided into the spaces of specular reflectance, diffuse reflectance, and internal reflectance. In preparing pastilles for FTIR spectroscopy measurements specimens of corrosion, products were separated from all specimens. CFRP sheet specimens were cut out in dimensions of 20 30 mm. FTIR absorption spe ctra were recorded at room temperature with Perkin Elmer spectrometer, model 2000. Prepared specimens were photographed in mid (4000 400 cm 1 ) infrared range. Operation of the FTIR was controlled by IRDM program, which at the same time enables the proces sing of the spectra as shown previously in section 3.2.3 Also, all specimens were characterized by IR spectroscopy (appendix C). 4 .3 Mechanical Testing 4 .3 .1 Capacity of L oading The load carrying capacity of the test beam was conducted to study the beh avior of CFRP steel beam. All specimens located to an MTS machine for mechanical testing, as shown in Figure 4. 9 provides the details of the test specimens, including the type of different durations from 12 Hr to 72 Hr. In addition, three specimens for co ntrol were shown in the table. A monotonic capacity load was applied to the beams at a rate of 1 mm/min until failure occurred. Load and displacement recorded by a built in load cell and the stroke of the loading head, respectively. The failure mode of the adhesive epoxy beam steel test and the CFRP sheet shown in Figure 4.10.

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80 4 .3 .2 Strain G age R eading Strain gages (gage length = 2 mm) fixed on the CFRP sheets at 25 mm on center to measure the progression of CFRP debonding, as shown in Figure.4. 1 After a week for curing and exposure period the beam steel test specimens were loaded carrying capacity of the test at a rate of 1.0 mm/min until failure occurred Figure4. 10 The performance of CFRP sheet under tension load was consistent over the ratio of cor rosion. A data acquisition system recorded all data. The results summarized in following the section. From the results and literature review the corrosion ratio has effect on the CFRP tension capacity. 4 4 Experimental Results 4.4.1 Analysis of Corrosion The corrosion rate was monitored using in situ electrochemical methods such mass loss method and Fourier Transformed Infrared Spectroscopy ( FTIR) method 4.4.1.1 Mass Loss Method This method was used to obtain the corros ion rates from the change of surface area and weight of specimens as shown in Table4.1 (a, b) It is observe that little change in the surface area as shown in Figure 4.11 but there few change in the weight as shown in Figure

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81 4. 1 2 The corrosion rates of b eam test specimens obtained by mass loss method are given in Table 4.3. The corrosion rate by mass loss method was slightly increasing (Figure 4. 1 5 ). This method was used to obtain the corrosion rates from current den sity and potential voltage of specimens during the corrosion cell as shown in Table 4.2. It observed that both current density and potential decreased as sho wn Figure 4.13 and Figure 4.14. The method given in Table Figure methods fully agreed as shown in Figure 4.17. 4.4. 1.3 Fourier Transformed Infrared Spectroscopy (FTIR) Testing The spectra were recorded as single channel spectra and afterward converted to absorbance spectra. The FTIR absorbance spectra of the corroded specimens as shown in Figure 4.18 and Figure 4.19. The examining corrosion from a short period of exposure to the long period of exposure was essentially the same as examining corrosion occurring in all specimens; each spectrum was a snapshot of corrosion occurring increased. Figure 4.18(a) the OH stretching frequency becomes clear at 3408 cm 1 Also, the C=O stretching frequency becomes clear too at 171 cm 1 An asymmetrical C O C stretching frequency of aryl alkyl ethers occurs at 1224 cm 1 The group at 1087 cm 1 corresponds to the

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82 symmetrical C O C stretching of alkyl aryl ether. The FTIR spectrum of the protecting film formed on the surface of the CFRP after immersed in the solution. After curing days don't indications of corrosion of the examined CFRP were noticed in any of the control specimen s. However after expose all specimens to chemical cell, corrosion was noticed in the all of specimens as shown in Figure 4.1 8 (a g). The C=O stretching frequency decreased from 1715 cm 1 to 1613 cm 1 An asymmetrical C O C stretching frequency of alkyl a ryl ether (1224 cm 1 ) disappeared. Also, disappeared the Symmetrical C O C stretching of alkyl aryl ether at (1087 cm 1 ). Figure 4.19 shows the difference between all of the specimens. 4.4.2 Load Displacement Response for the Beam Test The interfacial s trength of the test specimens summarized in Table 4.4. A comparison of load displacement for test categories of different period of corrosion shown in Figure 4.20. The control specimens (the Beam CR00 series) showed an average capacity of 62.92 kN. While t he ones with exposure after 72 Hr (the Beam CR72 series) exhibited a 31.70% lower capacity than the control specimens, on average. Figure 4.21 shows the load displacement response at midspan of the beams. The load carrying capacity of the beams was signif icantly influenced by the level of initial damage of corrosion in addition notch size. All series exhibited a linear response until an abrupt load drop was associated due to bond failure Figure. 4.21 (a). The stiffness of the respective specimens was more or less similar to each other, while their strength was slightly different. The cause could be explained by the fact that the amount of epoxy was not the same because of the experimental randomness to a certain extent. The specimens subjected to the exposu re

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83 corrosion demonstrated similar behavior Figure. 4.21 (b) to (g), while a local load drop noticed in some cases. Such an observation illustrates that the interface was partially damaged due to a period of exposure. 4.4.3 Strain Gage Response of the Be am Test Figure.4.22 shows the strains along the longitudinal CFRP sheets bonded with epoxy adhesives. CFRP strain development of the control beam with CFRP and epoxy (Beam CR00) given in Figure.4.22 (a). The strains of Gages 1,2,5,and 6 gradually increas ed up to a load of 60 kN beyond which some unstable strain development was associated due to the initiation of CFRP debonding at midspan in conjunction with stress concentrations at the flange cut Figure.4.22(a). An abrupt change in strain of Gages 2 and 5 was then observed, indicating the propagation of the CFRP debonding towards the direction of Gage 5 Figure.4.22 (b). Development of CFRP strain profiles summarized in Figure 4.23. Control specimen revealed a typical CFRP strain history with a gradual increase in strain at joint (mid joint of the specimen), followed by rapid CFRP debonding as shown in Figure. 4.23(a). The specimen with 72hr exposure illustrated lower strain development in comparison to control specimen with no corrosion and some residua l strains recorded when the beam failed Figure.4.23 (g).

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84 4.4. 4 PI Gage Response of the Beam Test Figure.4.24 shows the PI gage response of the beam test PI gage development of the control beam (Beam CR00 ) is given in Fig ure 4.24 (a) T he PI Gages Tensio n gradually increased up to a load of 60 kN beyond which some unstable strain development was associated due to the initiation of CFRP debonding at midspan in conjunction with stress concentrations at the flange cut Fig ure 4.24 (a). 4.4. 5 Failure Mode of Beam Test Specimen The failure mode of the experimental and predicted beams summarized. Figure.4.25 shows the effect of initial damage on the behavior of crack mouth opening displacement (CMOD) of the beams. The complete descending branch of the experime ntal CMOD did not predict The CMOD linearly increased with load before yielding of the beams, as shown in Figures. 4.25(a) 4.25(c). The linearity of the measured l oad CMOD was maintained up to 62.8 and 72.7% of the ultimate load, on average, for the control beam and 72Hr beams, respectively. The CMOD measured at peak load of the control beams varied from 1.65 to 3.85 mm, whereas that of the damage of beams was from 1.53 to 3.43 mm as shown in Figure.4.25 (d). The predicted CMOD values at the peak were within these ranges. The post peak behavior of the CMOD was significantly influenced by the ratio of corrosion as shown in Figure.4.25; the lower the ratio, the greater the stiffness softening. The course observation could be explained by the fact that the energy absorbed in the beam with a low corrosion ratio was greater than that with a high corrosion ratio (primarily because of the high load

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85 carrying capacity).And thu s the internally stored energy of the former tended to be abruptly released when the beam failed. For instance, Beam CR60 exhibited more gradual load softening than Beam CR12 because the absorbed energies of these beams up to the peak load were 42.97 and 5 8.53 kN Figure.4.25, respectively. Figure 4.26 shows the failure mode of the beam test. The control specimens with no corrosion display typical CFRP debonding failure Figure.4.26 (a) and the spotless failure surface indicates adhesion failure has dominate d the CFRP steel interface rather than cohesion failure. In addition, the specimens with corrosion after 72 Hr have shown CFRP debonding failure Figure. 4.26(b). Additional failure modes of corrosion at 12 Hr to 72 Hr shown in Figure. 4. 8 (a) (g). And also, Figure 4. 2 0 demonstrates various failure modes of the control and homogeneous bond beams with unstrengthen beam Typical ductile fracture observed for the control C0 beam, induced by stress concentrations at the corner of the flange cut as shown in Figure .4.26 (a). The failure of the beams given in Figure.4.2 6 All b eam and also beam CR72 failed by web fracture Figure.4.26 (a) and CFRP debonding noted in the epoxy bond regions Figure .4.26 (b).

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86 4 5 Summary and Conclusion This chapter has discussed t he residual behavior of CFRP sheet embedded in the steel substrate when subjected to elevated corrosion exposure from 12 Hr to 72 hr. One type of adhesives was used to bond the strips. Test specimens were conditioned in the predefined corrosion environment until 72 hours and mechanically loaded to failure. Interfacial strength between the CFRP and steel measured, and corresponding failure mode studied. These technical results are part of an ongoing research program examining the performance of CFRP strength ening system for steel structures with a focus on material and structure level investigations. Some preliminary conclusions are drawn as follows. ratio was in fluenced by period of exposure from 12 Hr to 72 Hr. The capacity of the CFRP steel interface was, however, affected by corrosion exposure within this boundary. corrosi on, even though the high ratio of corrosion showed a consistent capacity over the first two period of exposure to the corrosion increase.

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87 Table 4.1 (a) Test matrix Table 4.1 (b) Test matrix ID Type of Environmental Effect The loss of mass ( Kg ) Initial After exposure Individual Average STDEV Beam 1to 3 CR00 0 Hr/ELC 19.35 19.35 0.00 0.00 0.00 Beam 1CR12 19.38 19.37 0.02 0.03 0.01 Beam 1CR12 12 Hr/ELC 19.13 19.10 0.04 Beam 1CR12 19.26 19.23 0.03 Beam 1CR24 19.04 18.69 0.35 0.15 0.18 Beam 1CR24 24 Hr/ELC 19.12 19.10 0.03 Beam 1CR24 19.1 2 19.05 0.07 Beam 1CR36 19.23 18.96 0.27 0.42 0.14 Beam 1CR36 36 Hr/ELC 19.46 19.01 0.46 Beam 1CR36 19.35 18.82 0.53 Beam 1CR48 19.15 18.73 0.42 0.45 0.07 Beam 1CR48 48 Hr/ELC 19.13 18.60 0.54 Beam 1CR48 19.23 18.82 0.41 Beam 1CR60 19.04 18.51 0.53 0.48 0.18 Beam 1CR60 60 Hr/ELC 18.97 18.69 0.28 Beam 1CR60 19.14 18.51 0.64 Beam 1CR72 17.70 17.24 0.46 1.17 0.61 Beam 1CR72 72 Hr/ELC 18.78 17.24 1.55 Beam 1CR72 18.95 17.46 1.49 ELC Electrochemical cell ID Type of Environmental Effect Surface Area ( cm 2 ) Individual Average STDEV Beam 1to 3 CR00 0 Hr/ELC 6144.69 6144.69 0.00 Beam 1CR12 6129.19 6128.67 0.46 Beam 1CR12 12 Hr/ELC 6128.32 Beam 1CR12 6128.50 Beam 1CR24 6097.19 6095.95 5.82 Beam 1CR24 24 Hr/ELC 6101.06 Beam 1CR24 6089.61 Beam 1CR36 6048.1 1 6044.11 3.62 Beam 1CR36 36 Hr/ELC 6043.17 Beam 1CR36 6041.06 Beam 1CR48 6044.17 6045.08 1.45 Beam 1CR48 48 Hr/ELC 6044.33 Beam 1CR48 6046.75 Beam 1CR60 6032.89 6033.62 3.32 Beam 1CR60 60 Hr/ELC 6030.73 Beam 1CR60 603 7.24 Beam 1CR72 6009.05 6004.52 6.70 Beam 1CR72 72 Hr/ELC 6007.68 Beam 1CR72 5996.82

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88 Table 4.2 Test specimens for electrical cell ID Type of Environmental Effect Potential ( V ) Current density (A/cm 2 ) Individual Average STDEV Individual Average STDEV Beam 1CR12 Beam 2CR12 Beam 3CR12 0 Hr/ELC 11.99 10.84 1.00 2.0E+05 1.9E+05 5.6E +03 10.34 1.9E+05 10.18 1.9E+05 Beam 1CR12 10.12 10.38 0.62 1.5E+05 1.5E+05 4.0E+03 Beam 2CR12 12 Hr/ELC 9.93 1.5E+05 Beam 3CR12 11.09 1.5E+05 Beam 1CR24 5.72 6.13 0.37 5.9E+04 6.0E+04 6.2E+03 Beam 2CR24 24 Hr/ELC 6.4 2 5.4E+04 Beam 3CR24 6.26 6.6E+04 Beam 1CR36 5.15 4.83 0.44 5.2E+04 4.4E+04 9.3E+03 Beam 2CR36 36 Hr/ELC 4.99 4.7E+04 Beam 3CR36 4.33 3.4E+04 Beam 1CR48 4.68 4.56 0.20 3.2E+04 3.1E+04 6.5E+03 Beam 2CR48 48 Hr/E LC 4.32 2.4E+04 Beam 3CR48 4.67 3.7E+04 Beam 1CR60 3.53 3.40 0.24 2.9E+04 2.4E+04 5.0E+03 Beam 2CR60 60 Hr/ELC 3.54 1.9E+04 Beam 3CR60 3.12 2.3E+04 Beam 1CR72 0.78 0.81 0.17 1.4E+04 1.4E+04 1.3E+03 Beam 2CR72 7 2 Hr/ELC 1.00 1.5E+04 Beam 3CR72 0.67 1.2E+04 ELC Electrochemical c ell

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89 Table 4.3 Corrosion rate by mass loss and Faraday law ID Type of Environmental Effect Corrosion rate by mass loss( mm/y ) Corrosion ra te by Faraday law( mm/y ) Individual Average STDEV Individual Average STDEV Beam 1 3 CR00 0 Hr/ELC 0.00 0.00 0.00 0.00 0.00 0.00 Beam 1CR12 0.03 0.05 0.02 0.04 0.07 0.02 Beam 2CR12 12 Hr/ELC 0.07 0.09 Beam 3CR12 0.06 0.07 Beam 1CR24 0.64 0.27 0.32 0.65 0.28 0.32 Beam 2CR24 24 Hr/ELC 0.05 0.05 Beam 3CR24 0.12 0.14 Beam 1CR36 0.49 0.77 0.25 0.65 0.84 0.19 Beam 2CR36 36 Hr/ELC 0.85 1.02 Beam 3CR36 0.98 0.85 Beam 1CR48 0.77 0.84 0.13 0.84 0.87 0.07 Beam 2C R48 48 Hr/ELC 0.99 0.81 Beam 3CR48 0.76 0.95 Beam 1CR60 0.98 0.89 0.34 1.22 0.93 0.44 Beam 2CR60 60 Hr/ELC 0.52 0.43 Beam 3CR60 1.18 1.14 Beam 1CR72 0.86 2.16 1.13 0.62 1.51 0.80 Beam 2CR72 72 Hr/ELC 2.87 2.18 Beam 3CR72 2.77 1.73

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90 Table 4.4 Test results of specimens ID Type of Environmental Effect Ultimate load (kN) Individual Average STDEV Beam 1CR00 62.91 62.92 0.29 Beam 1CR00 0 Hr/No corrosion 63.21 Beam 1CR00 62.64 Beam 1CR12 58.2 58.53 0.95 Beam 2CR12 12 Hr/ELC 59.54 Beam 3CR12 57.86 Beam 1CR24 54.23 54.03 0.08 Beam 2CR24 24 Hr/ELC 54.35 Beam 3CR24 53.52 Beam 1CR36 49.01 48.18 1.18 Beam 2CR36 36 Hr/ELC 47.34 Beam 3CR36 48.74 Beam 1CR48 46.87 46.79 0.28 Beam 2CR48 48 Hr/ELC 46.47 Beam 3CR48 47.03 Beam 1CR60 45.64 45.62 0.59 Beam 2CR60 60 Hr/ELC 44.8 Beam 3CR60 46.43 Beam 1CR72 43.13 42.97 0.47 Beam 2CR72 72 Hr/ELC 42.46 Beam 3CR72 4 3.31

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91 Figure 4.1 Beam details and test setup (unit: mm)

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92 ( a ) ( b ) ( c ) ( d ) Figure 4.2 Beam preparation: (a) cutting the beam; (b) grind the beam; (c) clean the surface; (d) flange cut ( a ) ( b ) Figure 4.3 Preparation of a specimen before bonding: (a) precut CFRP sheets; (b) prepared beams

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93 ( a ) ( b ) ( c ) Figure 4.4 Beam test specimens: (a) m ixing an epoxy adhesive; (b) epoxy bonding; (c) after curing ( a) ( b) Figure 4.5 Setup for accelerated corrosion testing :(a) schematic ; (b) test picture

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94 ( a ) ( b ) ( c ) ( d ) Figure 4. 6 Measuring dimensions of specimen: (a) thickness of flange; (b) total depth ; (c) thickness web ; (d) width flange ( a ) ( b ) Figure 4.7 Measuring weight of specimen: (a) before corrosion; (b) after corrosion

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95 (a) ( b ) ( c ) ( d ) ( e ) ( f ) ( g ) Figure 4.8 Comparison of specimens: (a) cont rol beam ; (b) after 12 Hr ; (c) after 24 Hr ; (d) after 36 Hr ; (e) after 48 Hr ; (f) after 60 Hr ; (g) after 72 Hr

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96 Figure 4.9 Flexural test Figure 4.10 Strain gages for tension flange

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97 Figure 4.11 Variation of current surf ace area with time 0 1000 2000 3000 4000 5000 6000 7000 0 12 24 36 48 60 72 Surface area ( cm 2 ) Time (Hr) Individual Average 5900 6000 6100 6200 6300 0 12 24 36 48 60 72 Surface area ( cm 2 ) Time (Hr) Individual Average

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98 Figure 4.12 Variation of mass loss with time Figure 4.1 3 Variation of potential 0 0.5 1 1.5 2 0 12 24 36 48 60 72 The loss of mass( Kg ) Time (Hr) Individual Average STDEV 0 5 10 15 20 0 12 24 36 48 60 72 Potential ( V) Time (Hr) Individual Average STDEV

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99 Figure 4.1 4 Variation of current density with time Figure 4 15 Corrosion Rate obtained by the L oss of M ass M ethod 0.0E+0 1.0E+5 2.0E+5 3.0E+5 0 12 24 36 48 60 72 Current dencity (A/cm2) Time (Hr) Individual Average STDEV 0 1 2 3 4 5 0 12 24 36 48 60 72 Corrosion rate (mm/y) Time (Hr) Individual Average STDEV

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100 Figure 4.16 Corrosion Figure 4.17 0 1 2 3 4 5 0 12 24 36 48 60 72 Corrosion rate (mm/y) Time (Hr) Individual Average STDEV 0 1 2 3 4 5 0 12 24 36 48 60 72 Corrosion rate (mm/y) Time (Hr) AverageFaraday law Averagemass loss method

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101 (a) (b ) -0.05 0.00 0.05 0.10 0.15 0.20 0.25 550 1,050 1,550 2,050 2,550 3,050 3,550 4,050 Absorbance Wavenumber, cm 1 -0.05 0.00 0.05 0.10 0.15 0.20 0.25 550 1,050 1,550 2,050 2,550 3,050 3,550 4,050 Absorbance Wavenumber, cm 1

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102 (c) (d) -0.05 0.00 0.05 0.10 0.15 0.20 0.25 550 1,050 1,550 2,050 2,550 3,050 3,550 4,050 Absorbance Wavenumber, cm 1 -0.05 0.00 0.05 0.10 0.15 0.20 0.25 550 1,050 1,550 2,050 2,550 3,050 3,550 4,050 Absorbance Wavenumber, cm 1

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103 (e) (f) -0.05 0.00 0.05 0.10 0.15 0.20 0.25 550 1,050 1,550 2,050 2,550 3,050 3,550 4,050 Absorbance Wavenumber, cm 1 -0.05 0.00 0.05 0.10 0.15 0.20 0.25 550 1,050 1,550 2,050 2,550 3,050 3,550 4,050 Absorbance Wavenumber, cm 1

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104 (g) Figure 4. 18 Test specimens For FTIR: (a) Contorol beam;(b) After 12 Hr ; (c) at 24 Hr; (d) at 36 Hr; (e) at 48 Hr; (f) at 60 Hr ; (g) at 72 Hr -0.05 0.00 0.05 0.10 0.15 0.20 0.25 550 1,050 1,550 2,050 2,550 3,050 3,550 4,050 Absorbance Wavenumber, cm 1

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105 Figure 4. 19 Comparison of FTIR for all specimens with control beam -0.05 0.00 0.05 0.10 0.15 0.20 0.25 550 1,050 1,550 2,050 2,550 3,050 3,550 4,050 Absorbance Wavenumber, cm 1 ELC_12hr ELC_24hr ELC_36hr Control Beam -0.05 0.00 0.05 0.10 0.15 0.20 0.25 550 1,050 1,550 2,050 2,550 3,050 3,550 4,050 Absorbance Wavenumber, cm 1 ELC_48hr ELC_60hr ELC_72hr Control Beam

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106 Figure 4. 20 Test results of specimens 0 20 40 60 80 0 12 24 36 48 60 72 Ultimate load (kN) Time (Hr) Individual Average STDEV Unstrengthed beam

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107 ( a ) ( b ) 0 20 40 60 80 0 5 10 15 20 Load (kN) Displacemant (mm) Beam-1 Beam-2 Beam-3 0 20 40 60 80 0 5 10 15 20 Load (kN) Displacemant (mm) Beam-1 Beam-2 Beam-3

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108 ( c ) ( d ) 0 20 40 60 80 0 5 10 15 20 Load (kN) Displacemant (mm) Beam-1 Beam-2 Beam-3 0 20 40 60 80 0 5 10 15 20 Load (kN) Displacemant (mm) Beam-1 Beam-2 Beam-3

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109 ( e ) ( f ) 0 20 40 60 80 0 5 10 15 20 Load (kN) Displacemant (mm) Beam-1 Beam-2 Beam-3 0 15 30 45 60 0 5 10 15 20 Load (kN) Displacemant (mm) Beam-1 Beam-2 Beam-3

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110 (g) Figure 4. 21 Load displacemant behavior of specimens:; ( a) contorol beam ; (b) after 12 Hr; (c) after 24 Hr ; (d) after 36 Hr ; (e) after 48 Hr ; (f) after 60 Hr; (g) after 72 Hr ( a ) 0 20 40 60 80 0 5 10 15 20 Load (kN) Displacemant (mm) Beam-1 Beam-2 Beam-3 0 20 40 60 80 -0.001 0 0.001 0.002 0.003 0.004 Load (kN) Strain #1 #2 #3 #4 #5 #6

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111 ( b ) ( c ) 0 20 40 60 80 -0.001 0 0.001 0.002 0.003 0.004 Load (kN) Strain #1 #2 #3 #4 #5 #6 0 20 40 60 80 -0.001 0 0.001 0.002 0.003 0.004 Load (KN) Strain #1 #2 #3 #4 #5 #6

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112 ( d ) ( e ) 0 20 40 60 80 -0.001 0 0.001 0.002 0.003 0.004 Load (KN) Strain #1 #2 #3 #4 #5 #6 0 20 40 60 80 -0.001 0 0.001 0.002 0.003 0.004 Load (kN) Strain #1 #2 #3 #4 #5 #6

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113 ( f ) ( g ) Figure 4.2 2 Load strain behavior of specimence: (a) control beam 0 Hr : strain gages 1 6; (b) After 12 Hr : strain gages 1 6 ; (c) at 24 Hr : strain gages 1 6 ; (d) at 36 Hr : strain gages 1 6 ; (e) at 48 Hr : strain gages 1 6 ; (f) at 60 Hr : strain ga ges 1 6 ; (g) at 72 Hr : strain gages 1 6. 0 20 40 60 80 -0.001 0 0.001 0.002 0.003 0.004 Load (kN) Strain #1 #2 #3 #4 #5 #6 0 20 40 60 80 -0.001 0 0.001 0.002 0.003 0.004 Load (kN) Strain #1 #2 #3 #4 #5 #6

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114 ( a ) ( b ) 0 0.001 0.002 0.003 0.004 -150 -100 -50 0 50 100 150 Strain Distance from midspan (mm) 25%Pu 50%Pu 75%Pu 100%Pu 0 0.001 0.002 0.003 0.004 -150 -100 -50 0 50 100 150 Strain Distance from midspan (mm) 25%Pu 50%Pu 75%Pu 100%Pu

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115 ( c ) ( d ) 0 0.001 0.002 0.003 0.004 -150 -100 -50 0 50 100 150 Strain Distance from midspan (mm) 25%Pu 50%Pu 75%Pu 100%Pu 0 0.001 0.002 0.003 0.004 -150 -100 -50 0 50 100 150 Strain Distance from midspan (mm) 25%Pu 50%Pu 75%Pu 100%Pu

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116 ( e ) ( f ) 0 0.001 0.002 0.003 0.004 -150 -100 -50 0 50 100 150 Strain Distance from midspan (mm) 25%Pu 50%Pu 75%Pu 100%Pu 0 0.001 0.002 0.003 0.004 -150 -100 -50 0 50 100 150 Strain Distance from midspan (mm) 25%Pu 50%Pu 75%Pu 100%Pu

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117 (g) Figure 4.2 3 S train development along CFRP : (a) control beam 0 Hr; (b) After 12 Hr ; (c) at 24 Hr ; (d) at 36 Hr; (e) at 48 Hr; (f) at 6 0 Hr; (g) at 72 Hr (a) 0 0.001 0.002 0.003 0.004 -150 -100 -50 0 50 100 150 Strain Distance from midspan (mm) 25%Pu 50%Pu 75%Pu 100%Pu 0 20 40 60 80 -0.005 -0.003 -0.001 0.001 0.003 0.005 Load (kN) Strain Compression Tension

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118 ( b ) ( c ) 0 20 40 60 80 -0.005 -0.003 -0.001 0.001 0.003 0.005 Load (kN) Strain Compression Tension 0 20 40 60 80 -0.005 -0.003 -0.001 0.001 0.003 0.005 Load (kN) Strain Compression Tension

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119 ( d ) ( e ) 0 20 40 60 80 -0.005 -0.003 -0.001 0.001 0.003 0.005 Load (kN) Strain Compression Tension 0 20 40 60 80 -0.005 -0.003 -0.001 0.001 0.003 0.005 Load (kN) Strain Compression Tension

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120 ( f ) (g) Figure 4.2 4 Load PI Gages behavior of specimence: (a) Contorol beam (b) After 12 Hr ; (c) at 24 Hr ; (d) at 36 Hr ; (e) at 48 Hr ; (f) at 60 Hr ; (g) at 72 Hr 0 20 40 60 80 -0.005 -0.003 -0.001 0.001 0.003 0.005 Load (kN) Strain Compression Tension 0 20 40 60 80 -0.005 -0.003 -0.001 0.001 0.003 0.005 Load (kN) Strain Compression Tension

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121 (a) ( b ) 0 20 40 60 80 0 2 4 6 Load (kN) CMOD (mm) Tension 0 20 40 60 80 0 2 4 6 Load (kN) CMOD (mm) Tension

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122 ( c ) ( d ) 0 20 40 60 80 0 2 4 6 Load (kN) CMOD(mm) Tension 0 20 40 60 80 0 2 4 6 Load (kN) CMOD (mm) Tension

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123 ( e ) ( f ) 0 20 40 60 80 0 2 4 6 Load (kN) CMOD (mm) Tension 0 20 40 60 80 0 2 4 6 Load (kN) CMOD (mm) Tension

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124 (g) Figure 4.2 5 Load crack mouth opening displacement : (a) Contorol beam ; (b) After 12 Hr ; (c) at 24 Hr ; (d) at 36 Hr ; (e) at 48 Hr ; (f) at 60 Hr; (g) at 72 Hr 0 20 40 60 80 0 2 4 6 Load (kN) CMOD (mm) Tension

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125 ( a ) ( b ) Figure. 4.2 6 Failure mode of beam: (a) fracture crack; (b) CFRP debonding. Fracture crack CFRP debonding

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126 5. Conclusion and Recommendation This chapter contains conclusions based on the findings of this study. In addition, a several recommendations are provided. The value of each sample used in this study, whether in tensile or compression test, represented the average value of three specimens that made these results reasonable and dependable. 5.1 Conclusions on Interface test Specimen Behavior Regarding the corrosion ef fect on tensile behavior work included testing one group of sample. All specimens represented samples of the joint reinforced by CFRP. The results compared with the intact sample. For corrosion effect on tensile behavior, the control specimens were chosen to represent the effect of corrosion. Then, the reinforced sample of the control beams were compared with reinforced samples subjected to different periods effect of corrosion (12 Hr to 72 Hr) hours. Corrosion rate of effects tested separately. The analysi s of these results led to the following conclusions: Corrosion effect caused a gradual reduction in mass loss when the time under water increased. The reduction recorded a minimum value of about 3.7% less than the original sample at 12 hours, and a max imum value of about 16.4% less than the original sample at 72 hours. However, the periodic exposures to corrosion like period between 12 Hr and 60 Hr seriously had not affected the surface area but it was reduced to about 1 8 6 % less than the original speci mens for 72 Hr.

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127 Load displacement behavior is largely affected by the different period effect of corrosion. Specimens exposed to different period effect of corrosion (12 Hr to 72 Hr) hours, show a noticeable effect on ultimate tensile force compared with the control specimens. The interface joint under 12 Hr recorded an ultimate tensile force approximately 19.7% less than the control one, the sample under 24 Hr recorded 26.6 % less than the original. While the specimens under 36 Hr were 2 1.7 % less than the original. Also, the specimens under 48 Hr recorded an ultimate tensile force approximately 28.7% less than the control one, the sample under 60 Hr recorded 50 % less than the control. While the specimens under 72 Hr were 77.8 % less than the control. The strain values of the CFRP strip provided by the strain gages were not similar for all specimens but had the same stiffener. 5.2 Conclusions on Beam Test in Flexure behavior Beam tests included a comparison of 30 mm notched specimens rehabil itated with CFRP and those having the same notch with CFRP to find the effect of CFRP on the Three point load of corroded specimens. The Beam 1 to 3 CR00 reinforced samples chosen as control specimens. These beams compare with other specimens affected by d ifferent degrees of corrosion or different periods of corrosion in order to find the environmental effect on the ultimate load of rehabilitated specimens. From theses results of these tests, the following conclusions have drawn:

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128 The CFRP sheet used in t his study to increase the ultimate loads by about 39.6% compared to the non rehabilitated sample. Specimens exposed to corrosion affects (12 Hr until 60 Hr) did not record a remarkable effect on surface area compared with the control sample but it was reduced to about 2.3% less than the original specimens for 72 Hr Similar to interface behavior, the sample subjected to corrosion effect between 12 Hr and 72 Hr recorded the increase in mass loss of about 10.9 % less than the control sample. Specimens ex posed to different period effect of corrosion (12 Hr to 72 Hr) hours, show a noticeable effect on the ultimate load compared with the control specimens. The specimens under 12 Hr recorded an ultimate load approximately 6.9% less than the control one, th e s ample under 24 Hr recorded 1 4 .1 % less than the control. While the specimens under 36 Hr were 2 3 4 % less than the control. Also, the specimens under 48 Hr recorded an ultimate tensile force approximately similar to the control one, the sample under 60 Hr re corded 27.5 % less than the original. While the specimens under 72 Hr were 31.7 % less than the control.

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129 5. 3 Recommendations and future works In this section, some recommendations and future works are made regarding the application of CFRP in th e rehabilitation of corroded steel members. These recommendations and proposals based the results of the current investigation: The shape of the notch used to represent corrosion can change load deformation behavior and stress distribution. That means t he different shapes of notches, even if they have the same size of the area, can provide different results of stress distribution and result in different yield loads and ultimate loads. Further experimental and numerical studies on the relationship between notch size and shape and its effect on stress needed. The influence of environmental factors on this stresses of artificially corroded steel members should be study. As result, it is recommended that the same notch size and shape be chosen and located wi thin the same position on all specimens so that the unknown effects of the notch can be similar and equal for all specimens Due to the limited availability of resources, this study was limited to one type of CFRP sheet with low elastic modulus. Study of the application of different types of FRP with a wide range of elastic modulus. The changing of adhesive material can substantially affect the results as the adhesive bond is considered to be the weakest point in this rehabilitation system. More resear ch is required

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130 to identify an adhesive material which is both suitable for bonding CFRP to steel, and highly resistant to environmental effects. The use of CFRP sheet and the adhesive material, used in this study, in locations continually experiencing a rate of corrosion differences (between 12Hr and 72 Hr) is not recommended for beam behavior.

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131 R EFERENCES and loading frequency on fatigue life of a CFRP bar in concr Composites in Infrastructure, Tucson, Arizona, USA, Vol. 2, pp. 203 210. Al inforcement pp. 123 127. Al Sulaimani, G.J., Sharif, A., Basunbul, I.A., Baluch, M.H., and Ghaleb, B.N.(1994), Vol. 91, No. 3, pp.458 463. Symposium on Non Metallic (FRP) Reinforcement for Concrete Structures, Sapporo, Japan, Vol. 2, pp. 203 210. Audenaert, K., Ta rupture of FRP state of the Structures (FRPRCD 5), Vol. 2, pp.518 526. e behavior of FRP elements for prestressed concrete

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132 International Symposium on FRP Reinforcement for Concrete Structures, Vancouver, Canada. gradation of carbon FRP composites and E Arizona, USA, 5 7 January, Vol. 1, pp. 86 92. Ewan, lity of FRP in concrete current on FRP Composite in Civil Engineering, 12 15 December, Hong Kong, China, pp. 1497 1507. FIB Bulletin 10, 2000. Bond of Reinforcement in Concrete (FIB 10 ). Fdration International du Bton, Lausanne, Switzerland. Proceedings of the Second International Conference (CDCC 02): Durability of Fiber Reinforced Polymer (FRP) Composite for Construction, May 29 31, pp.273 284. Proceeding s of the Third International Symposium on Non Metallic (FRP) Reinforcement for Concrete Structures, Sapporo, Japan, 14 16 Oct. Vol. 1, pp. 419 426. of retrofitted RC c International Symposium on Non Metallic (FRP) Reinforcement for Concrete Structures, Sapporo, Japan, 14 16 Oct., Vol. 2, pp. 547 545.

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133 ing reinforced concrete columns using Metallic (FRP) Reinforcement for Concrete Structures, Sapporo, Japan, 14 16 Oct., Vol. 1, pp. 555 562. Masukawa, J., Akiyama, H., and Saito, H. ( International Symposium on Non Metallic (FRP) Reinforcement for Concrete Structures, Sapporo, Japan, 14 16 Oct. Vol. 1, pp. 411 418. prestressed concrete beams with non the Third International Symposium on Non Metallic (FRP) Reinforcement fo r Concrete Structures, Sapporo, Japan, 14 16 ,Vol. 2, pp. 775 782. Proceedings of the Specialty Conference: Advanced Composite Materials in Civil Engineering Structures, ASCE, pp. 224 232. Non Metallic Continuous Reinforcement, Vancouver, Canada, pp. 117 131. No. 3. site materials with application to bridge: state of the

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134 tests of prestresses concrete beams reinforced with carbo n fiber sheets in water Metallic (FRP) Reinforcement for Concrete Structures, Sapporo, Japan, 14 16 Oct., Vol. 1, pp. 387 394. Okano, M., Ohuchi, H., Moriyama, T., Matsumoto, N., and Wa Symposium on Non Metallic (FRP) Reinforcement for Concrete Structures, Sapporo, Japan, 14 16 Oct., Vol. 1, pp. 403 410. Spadea, G., Bencardino, F., of the Third International Symposium on Non Metallic (FRP) Reinforcement for Concrete Structures, Sapporo, Japan, 1 4 16 Oct. 97, Vol. 1, pp. 629 636. Radomski W. (2002): Bridge rehabilitation, ICP, London. pp 1 6, 34 43, 208 279. Journal, Vol. 91, No.3, pp. 346 354. Arizo na, USA, 5 7 January, Vol. 2, pp. 524 538. Tilly G.P., Matthews S.J., Deacon D., De Voy J. & Jackson P.A. (2008): Iron and steel bridges: condition apprisal and remedial treatment, CIRIA, London.

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135 Proceedings of the Second International RILEM Symposium (FRPRCS 2): Non Metallic (FRP) Reinforcement for Concrete Structures, Edited by L. Taerwe, Ghent, 23 25 August, pp. 100 107. Proceedings of the International Conference on FRP Composite in Civil Engineering, 12 15 December, Hong Kong, China, pp. 85 96. com 7 January, Vol. 1, pp. 221 234. Creep rupture of FRP rods Metallic Reinforcement for Concrete Structures, Vol. 2, pp 179 186.

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136 Appendix Appendix A Presents additional detailed pictur es of the process for the CFRP with Steel testing that have been done in which you can see the test setup

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140 Appendix B P resents the bond perf ormance of the corrosion in which you can see the failure mode from the pictures.

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141 Appendix C P resents the bond performance of characteristic Infrared Absorption Frequencies