Download or read book Evaluation of the Corrosion Behaviour of Continuously Galvanized Rebar written by Ibrahim Ogunsanya and published by . This book was released on 2016 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: De-icing/anti-icing salts used during the winter season are the major culprit in limiting the durability of reinforced concrete structures. The salts induce corrosion of rebar, by penetrating the concrete and breaking down the protective film formed on the steel in the high alkaline environment of the concrete. Since the corrosion products occupy a volume larger than that of the corroded steel, they crack the concrete. The use of more corrosion resistant alloys is one method of improving the durability of reinforced concrete structures. Conventional hot-dipped galvanized steel (HDG) is an economical alternative to black steel mainly because: the zinc coating has a higher chloride threshold and, when the bar eventually corrodes, it provides additional protection to the base steel through its sacrificial anode effect, its corrosion products are soluble and do not crack the concrete, and it forms a stable protective film even in low pH concrete. However, its major drawback is the brittle and less corrosion resistant (than pure Zn) Fe-Zn intermetallic compounds (IMC) formed in the coating. To remedy this, a ductile pure zinc coating produced by a continuously galvanizing process has recently been developed. Small amounts of aluminum are added to the zinc bath with the goal of forming an Fe-Al inhibition layer between the steel and the zinc coating. In this project, three prototypes of the continuously galvanized rebar (CGR) grades, C1, C2 and C3 were electrochemically assessed, using galvanostatic pulse (GP) and linear polarization resistance (LPR) techniques, to evaluate and compare the corrosion behaviour of these bars against HDG and black steel. A second goal of the project was to identify the characteristic electrochemical potentials of HDG steel and CGR coatings to provide similar guidelines to those provided by ASTM C876 for assessing the probability of corrosion of uncoated carbon steel rebar in the field. All bars were cast in both non-cracked and cracked concrete, and exposed to a multi-chloride brine solution locally available and used across Ontario, Canada. Metallographic examination performed on the galvanized bars showed the non-uniformity of all coatings, particularly the CGR grades - some regions which were significantly less than the specified thickness, and some others were too thin to be detected. The coating thickness on the tested HDG, C1 and C2, and C3 bars were in the range of 105 - 250 [mu]m, 15 - 60 [mu]m, 5 - 33 [mu]m respectively. The aluminum content of the C3 bars, ~9%, was similar in range to “Galfan” steel. After weekly electrochemical testing for 64 weeks, the results showed that the C3 performed the same as black steel in both passive and active state. The C1 and C2 bars performed the same as HDG bars in the passive state and three to five times better than black steel in the active state. The HDG bars exhibited ten times better “corrosion performance” than black steel in both passive and active state. The time to corrosion initiation was not determined in the present project, as a result, “corrosion performance” is defined as the active corrosion rate after initiation. The electrochemical behaviour of galvanized bars has been attributed to their zinc thickness and/or the presence of significant aluminum content in the coatings. The corrosion product of the high Al containing bar, C3, appeared to affect the bonding between the bar and its concrete, which then negatively affected the electrochemical behaviour of the bar. To characterize the corrosion potentials of these galvanized bars, the passive and active corrosion potential values of all galvanized bars were in the range of -266 to -382 mV vs SCE and -345 to -686 mV vs SCE, respectively. Moreover, the HDG and C3 rebar grades are in the upper and lower end of the ranges, respectively. The potential guideline developed for accessing probability of corrosion of black steel in concrete suggests that when the potential is more positive than -335 mV vs SCE (or -410 mV CSE), there is low probability of corrosion, when it is more negative than -385 mV vs SCE (or 460 mV vs CSE), there is high probability of corrosion, and an uncertain region exists between these potentials.
Download or read book Evaluation of the Behaviour of Continuously Galvanized Rebar written by Ibrahim Ogunsanya and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: De-icing/anti-icing salts used during the winter season are the major culprit in limiting the durability of reinforced concrete structures. The salts induce corrosion of rebar, by penetrating the concrete and breaking down the protective film formed on the steel in the high alkaline environment of the concrete. Since the corrosion products occupy a volume larger than that of the corroded steel, they crack the concrete. The use of more corrosion resistant alloys is one method of improving the durability of reinforced concrete structures. Conventional hot-dipped galvanized steel (HDG) is an economical alternative to black steel mainly because: the zinc coating has a higher chloride threshold and, when the bar eventually corrodes, it provides additional protection to the base steel through its sacrificial anode effect, its corrosion products are soluble and do not crack the concrete, and it forms a stable protective film even in low pH concrete. However, its major drawback is the brittle and less corrosion resistant (than pure Zn) Fe-Zn intermetallic compounds (IMC) formed in the coating. To remedy this, a ductile pure zinc coating produced by a continuously galvanizing process has recently been developed. Small amounts of aluminum are added to the zinc bath with the goal of forming an Fe-Al inhibition layer between the steel and the zinc coating. In this project, three prototypes of the continuously galvanized rebar (CGR) grades, C1, C2 and C3 were electrochemically assessed, using galvanostatic pulse (GP) and linear polarization resistance (LPR) techniques, to evaluate and compare the corrosion behaviour of these bars against HDG and black steel. A second goal of the project was to identify the characteristic electrochemical potentials of HDG steel and CGR coatings to provide similar guidelines to those provided by ASTM C876 for assessing the probability of corrosion of uncoated carbon steel rebar in the field. All bars were cast in both non-cracked and cracked concrete, and exposed to a multi-chloride brine solution locally available and used across Ontario, Canada. Metallographic examination performed on the galvanized bars showed the non-uniformity of all coatings, particularly the CGR grades - some regions which were significantly less than the specified thickness, and some others were too thin to be detected. The coating thickness on the tested HDG, C1 and C2, and C3 bars were in the range of 105 - 250 μm, 15 - 60 μm, 5 - 33 μm respectively. The aluminum content of the C3 bars, ~9%, was similar in range to "Galfan" steel. After weekly electrochemical testing for 64 weeks, the results showed that the C3 performed the same as black steel in both passive and active state. The C1 and C2 bars performed the same as HDG bars in the passive state and three to five times better than black steel in the active state. The HDG bars exhibited ten times better "corrosion performance" than black steel in both passive and active state. The time to corrosion initiation was not determined in the present project, as a result, "corrosion performance" is defined as the active corrosion rate after initiation. The electrochemical behaviour of galvanized bars has been attributed to their zinc thickness and/or the presence of significant aluminum content in the coatings. The corrosion product of the high Al containing bar, C3, appeared to affect the bonding between the bar and its concrete, which then negatively affected the electrochemical behaviour of the bar. To characterize the corrosion potentials of these galvanized bars, the passive and active corrosion potential values of all galvanized bars were in the range of -266 to -382 mV vs SCE and -345 to -686 mV vs SCE, respectively. Moreover, the HDG and C3 rebar grades are in the upper and lower end of the ranges, respectively. The potential guideline developed for accessing probability of corrosion of black steel in concrete suggests that when the potential is more positive than -335 mV vs SCE (or -410 mV CSE), there is low probability of corrosion, when it is more negative than -385 mV vs SCE (or 460 mV vs CSE), there is high probability of corrosion, and an uncertain region exists between these potentials.
Download or read book Galvanized Steel Reinforcement in Concrete written by Stephen Yeomans and published by Elsevier. This book was released on 2004-11-26 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reinforced concrete is one of the most widely used modern materials of construction. It is comparatively cheap, readily available, and suitable for a variety of building and construction applications. Galvanized Steel Reinforcement in Concrete provides a detailed resource covering all aspects of this important material. Both servicability and durability aspects are well covered, with all the information needed maximise the life of buildings constructed from it. Containing an up-to-date and comprehensive collection of technical information and data from world renound authors, it will be a valuable source of reference for academics, researchers, students and professionals alike. Provides information vital to prolong the life of buildings constructed from this versatile material Brings together a disparate body of knowledge from many parts of the world into a concise and authoritative text Containing an up-to-date and comprehensive collection of technical information
Download or read book Corrosion of Steel in Concrete Structures written by Amir Poursaee and published by Woodhead Publishing. This book was released on 2023-02-20 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: Essential reading for researchers, practitioners, and engineers, this book covers not only all the important aspects in the field of corrosion of steel reinforced concrete but also discusses new topics and future trends. Theoretical concepts of corrosion of steel in concrete structures, the variety of reinforcing materials and concrete, including stainless steel and galvanized steel, measurements and evaluations, such as electrochemical techniques and acoustic emission, protection and maintenance methods, and modelling, latest developments, and future trends in the field are discussed. Comprehensive coverage of the corrosion of steel bars in concrete, investigating the range of reinforcing materials, and types of concrete Introduces the latest measuring methods, data collection, and advanced modeling techniques Second edition covers a range of new, emerging topics such as the concept of chloride threshold value, concrete permeability and chloride diffusion, the role of steel microstructure, and innovations in corrosion detection devices
Download or read book Corrosion Protection of Reinforcing Steels written by fib Fédération internationale du béton and published by fib Fédération internationale du béton. This book was released on 2009-01-01 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt: It has long been recognised that corrosion of steel is extremely costly and affects many industry sectors, including concrete construction. The cost of corrosion of steel reinforcement within concrete is estimated at many billions of dollars worldwide. The corrosion of steel reinforcement represents a deterioration of the steel which in turn detrimentally affects its performance and therefore that of the concrete element within which it has been cast. A great amount of work has been undertaken over the years concerning the prevention of corrosion of steel, including the application of coatings, which has included the study of the process of corrosion itself, the properties of reinforcing steels and their resistance to corrosion as well as the design of structures and the construction process. The objective of fib Bulletin 49 is to provide readers with an appreciation of the principles of corrosion of reinforcing steel embedded in concrete and to describe the behaviour of particular steels and their coatings as used to combat the effects of such corrosion. These include galvanised reinforcement, epoxy coated reinforcement, and stainless reinforcing steel. It also provides information on the relative costs of the materials and products which it covers. It does not deal with structure design or the process of construction or with the post-construction phase of structure management including repair. It is hoped that it will nevertheless increase the understanding of readers in the process of corrosion of reinforcing steels and the ability of key materials and processes to reduce its harmful effects.
Download or read book Corrosion of Reinforcing Steel in Concrete written by D. E. Tonini and published by ASTM International. This book was released on 1980 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Performance Evaluation of Corrosion Inhibitors and Galvanized Steel in Concrete Exposure Specimens written by Jerzy Zemajtis and published by . This book was released on 1999 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: Corrosion inhibitor admixtures (CIA) and galvanized reinforcing steel (GS) are used for the corrosion protection for reinforced concrete bridges. The results of a 3.5-year evaluation of exposure specimens containing CIA from three different manufacturers and GS are presented. The specimens were built to simulate four exposure conditions typical for concrete bridges located in the coastal region or inland where deicing salts are used. The exposure conditions were Horizontal, Vertical, Tidal, and Immersed Zones. The specimens were kept inside the laboratory and were exposed to weekly ponding cycles of 6% sodium chloride solution by weight. The methods used to assess the condition of the specimens included chloride concentration measurements, corrosion potentials, and corrosion rates. Additionally, visual observations were performed for identification of rust stains and cracking on concrete surfaces. The results of chloride testing indicate that the amount of chlorides present at the bar level is more than sufficient to initiate corrosion. Chloride and rapid permeability data indicate no significant difference either in a rate of chloride ingress or in the diffusion coefficients for concretes with and without CIA. Corrosion potentials were the most negative for the Bare Steel (BS) specimen prepared with the Armatec 2000 corrosion inhibitor and generally indicated a 90% probability of active corrosion. Corrosion potentials were similar for the two BS control specimens and the BS specimen prepared with Rheocrete 222 and generally indicated an uncertain probability of corrosion. Corrosion potentials were the least negative for the BS specimen prepared with DCI-S corrosion inhibitor and generally indicated a 90% probability of no corrosion. Rate of corrosion measurements were the highest for the BS control specimens and the one prepared with A2000 and the most recent data suggest corrosion damage in 2 to 10 years. Although early rate of corrosion measurements were higher or about the same as for BS control specimens, recent measurements were slightly lower for the specimen prepared with Rheocrete 222 and suggest corrosion damage in 10 to 15 years. Rate of corrosion measurements were consistently the lowest for the BS specimens prepared with DCI-S and indicate corrosion damage is expected in 10 to 15 years. The corrosion potential and rate of corrosion data indicate that DCI-S is the only CIA evaluated that clearly provides some level of corrosion protection. A direct comparison of the GS specimens to the BS specimens is not possible because the measured potential refers to the zinc oxide and not to the steel. Nevertheless, the potential data agree with the chloride and permeability data, as well as with the visual observations, and indicate the damaging effect of a high concentration of chloride ions on the GS. At low and moderate chloride exposures, however, GS does provide corrosion protection. Recommendations are to continue monitoring until sufficient cracking has occurred in all specimens to provide for making a better estimate of the service lives of CIA and GS used in the construction of concrete bridge components in Virginia. The specimens with CIA and one control (continuous reinforcement in the legs) should be taken to the Hampton Road North Tunnel Island and placed in the brackish water to a depth of the Immersed Zone at low tide for further exposure to chloride. The specimens with GS and the other control (non-continuous reinforcement in the legs) should remain in an outdoor exposure in Southwest Virginia like the Civil Engineering Materials Research Laboratory in Blacksburg, Virginia.
Download or read book Measurement Techniques and Evaluation of Galvanized Reinforcing Steel in Concrete Structures in Bermuda written by D. Stark and published by . This book was released on 1980 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The performance of galvanized reinforcing steel in concrete structures exposed to seawater in Bermuda was evaluated by measurements of chloride concentrations in the concrete, and average depths of corrosion of the galvanized coatings. Results indicate that little more than superficial corrosion of the coatings has occurred in 7- to 23-year-old normal-quality concretes containing as much as 10 times the chloride concentrations needed to induce corrosion of untreated steel. In all but one case the outer free zinc layer was still present on the coating. In these instances, the average depths of corrosion ranged from zero to 0.013 mm, with the amount of coating remaining ranging from 92 to 100 percent of the original thickness. Localized corrosion to the steel substrate was found only in uncompacted highly porous concrete in a poorly bonded cold joint.
Download or read book Influence of Alloying Elements Testing Solution and Surface Roughness on Corrosion Behaviour of Stainless Steel Reinforcing Bars written by Ibrahim Ogunsanya and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The province of Ontario has moved from applying rock salt crystals, predominantly impure sodium chloride, to locally available anti-icing brine solutions with chloride amounts as high as 21%. At the same time, the specified design service life of highway structures has increased from 50 years to 75 years. The exposure to aggressive chloride brines has increased the need for more corrosion resistant reinforcing bar (rebar) than the traditional carbon steel rebar. However, the high cost of many stainless steel rebar alloys made them a last resort when concrete reinforcement options are considered. A major factor for their high cost is the price of their major alloying elements. Therefore, the contributions of these elements towards passive film properties, pitting corrosion resistance, critical chloride threshold (CCRIT) values and overall corrosion performance in the presence of deleterious species in concrete, such as chlorides, must be ascertained. This research aimed to provide a critical evaluation of the various parameters affecting long term corrosion performance of different grades of stainless steel rebar in concrete exposed to anti-icing brines. The first step to achieving this was to determine the variation in pore solution compositions of different concrete mixes so that bars can be tested in a similar environment. To do this, cement pastes of varying admixed chloride content, cementitious materials and water-to-cementitious ratio (w/cm) were cast and their pore solutions were analyzed for ionic composition and pH. The results revealed increasing dissolution of sulphate ions with increasing admixed chloride ions in the pore solution. These actual solutions were used in subsequent assessment procedures involving electrochemical techniques such as Mott-Schottky analysis, potentiostatic linear and non-linear polarization resistance and cyclic potentiodynamic polarization techniques. The goal was to determine the passive film properties, pitting characteristics, critical chloride threshold (CCRIT) and relative corrosion performance of carbon steel and five grades stainless steel rebar. Results showed the addition of sulphates to testing solutions suppressed the damage from chloride ions on steel passive films, by forming iron and nickel sulphides in passive films that provided additional protection. Results also showed that testing in lower pH solution, as done by many researchers, is conservative and underestimates corrosion resistance. The influence of the expensive stainless steel alloying elements (Cr, Ni, Mo, Mn) on the corrosion parameters listed above were then investigated. Chromium significantly improved these properties by decreasing passive film defects and increasing CCRIT values of the rebar. Molybdenum did not improve the corrosion resistance in the austenitic alloys but was beneficial in duplex alloys by concentrating in the ferritic component. Nickel was found to improve the outer layer of passive films properties by forming an Fe-Ni spinel, while manganese improved the inner passive layer. It is necessary for these observations in corrosion behaviour of rebar to be consistent. Consequently, other factors potentially leading to variations in corrosion performance of stainless steel rebar alloys were examined. These included the influence of variability in composition, microstructure and surface roughness between batches of stainless steel alloys from different manufacturers, and results showed surface roughness to be the major and overwhelming factor in corrosion resistance. The most important observation has been that, for the particular concrete mixture used in this research, the critical chloride threshold concentration, found by extrapolation of the experimental data, was greater than the solubility limit of chlorides in cement pores. This implies that chloride induced corrosion of the stainless alloys would not be possible in this concrete in the absence of cracks or major flaws.
Download or read book The Effect of Galvanized Steel Corrosion on the Integrity of Concrete written by Zuo Quan Tan and published by . This book was released on 2007 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt: The major concern regarding the use of hot-dip galvanized (HDG) steel as reinforcement in concrete has been the high rate of corrosion experienced by the zinc during the first hours in the fresh, wet, and highly alkaline concrete. The present work was aimed at clarifying three issues associated with these concerns. The first involves the metallurgical phases at the surface of the zinc coating. The concentration of zinc at the surface is a function of processing procedures, surface treatment, and exposure to weathering. Differences in the coating surface composition influence the corrosion behaviour of HDG steel reinforcing bars when they are embedded in concrete. The second issue involves the increasing use of supplementary cementing materials in concrete, which change the chemistry of the concrete pore fluid, and also influence the corrosion. The third issue is that the initial corrosion is accompanied by hydrogen evolution, which could increase the pore volume of adjacent cement and thereby, decrease the bond stress between the concrete and the steel. In order to limit the hydrogen evolution, a chromate layer is applied after galvanizing. The results of the project have demonstrated that, during zinc corrosion in ordinary Portland cement (OPC) concrete, calcium hydroxyzincate formed on untreated HDG steel provided sufficient protection against corrosion. Therefore, it is concluded that treating HDG rebar with dilute chromic acid is unnecessary as a method of passivating zinc.
Download or read book Corrosion in Reinforced Concrete Structures written by H Böhni and published by Elsevier. This book was released on 2005-01-20 with total page 263 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reinforced concrete has the potential to be very durable and capable of withstanding a variety of adverse environmental conditions. However, failures in the structures do still occur as a result of premature reinforcement corrosion. In this authoritative book the fundamental aspects of this complex process are analysed; focusing on corrosion of the reinforcing steel, and looking particularly, at new scientific and technological developments. Monitoring techniques, including the newly developed online-monitoring, are examined, as well as the numerical methods used to simulate corrosion and perform parameter studies. The influence of composition and microstructure of concrete on corrosion behaviour is explored. The second half of the book, which deals with corrosion prevention methods, starts with a discussion on stainless steels as reinforcement materials. There are comprehensive reviews of the use of surface treatments and coatings, of the application of corrosion inhibitors and of the application of electrochemical techniques. In each case the necessary scientific fundamentals are explained and practical instances of use are looked at. This is an invaluable guide for engineers, materials scientists and researchers in the field of structural concrete. Fundamental aspects of corrosion in concrete are analysed in detail Explores how to minimise the effects of corrosion in concrete Invaluable guide for engineers, materials scientists and researchers in the field of structural concrete
Download or read book Handbook of Hot dip Galvanization written by Peter Maaß and published by John Wiley & Sons. This book was released on 2011-03-31 with total page 460 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hot-dip galvanization is a method for coating steel workpieces with a protective zinc film to enhance the corrosion resistance and to improve the mechanical material properties. Hot-dip galvanized steel is the material of choice underlying many modern buildings and constructions, such as train stations, bridges and metal domes. Based on the successful German version, this edition has been adapted to include international standards, regulations and best practices. The book systematically covers all steps in hot-dip galvanization: surface pre-treatment, process and systems technology, environmental issues, and quality management. As a result, the reader finds the fundamentals as well as the most important aspects of process technology and technical equipment, alongside contributions on workpiece requirements for optimal galvanization results and methods for applying additional protective coatings to the galvanized pieces. With over 200 illustrated examples, step-by-step instructions, presentations and reference tables, this is essential reading for apprentices and professionals alike.
Download or read book Corrosion of Steel in Concrete written by Luca Bertolini and published by John Wiley & Sons. This book was released on 2013-02-26 with total page 389 pages. Available in PDF, EPUB and Kindle. Book excerpt: Steel-reinforced concrete is used ubiquitously as a building material due to its unique combination of the high compressive strength of concrete and the high tensile strength of steel. Therefore, reinforced concrete is an ideal composite material that is used for a wide range of applications in structural engineering such as buildings, bridges, tunnels, harbor quays, foundations, tanks and pipes. To ensure durability of these structures, however, measures must be taken to prevent, diagnose and, if necessary, repair damage to the material especially due to corrosion of the steel reinforcement. The book examines the different aspects of corrosion of steel in concrete, starting from basic and essential mechanisms of the phenomenon, moving up to practical consequences for designers, contractors and owners both for new and existing reinforced and prestressed concrete structures. It covers general aspects of corrosion and protection of reinforcement, forms of attack in the presence of carbonation and chlorides, problems of hydrogen embrittlement as well as techniques of diagnosis, monitoring and repair. This second edition updates the contents with recent findings on the different topics considered and bibliographic references, with particular attention to recent European standards. This book is a self-contained treatment for civil and construction engineers, material scientists, advanced students and architects concerned with the design and maintenance of reinforced concrete structures. Readers will benefit from the knowledge, tools, and methods needed to understand corrosion in reinforced concrete and how to prevent it or keep it within acceptable limits.
Download or read book Metals Abstracts written by and published by . This book was released on 1998 with total page 1042 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Australian Journal for Chemical Engineers written by and published by . This book was released on 1981 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Stainless Steel in Concrete written by European Federation of Corrosion and published by Woodhead Publishing Limited. This book was released on 1996 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book High performance concrete pavements written by and published by . This book was released on 2002 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt:
