Dissertations / Theses on the topic 'Reinforcement corrosion'
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1
Ward-Waller, Elizabeth 1982. "Corrosion resistance of concrete reinforcement." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/31125.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005."June 2005."
Includes bibliographical references (leaves 39-40).
The objective of this thesis is to investigate the mechanism of corrosion of steel reinforcement in concrete and epoxy coated reinforcing bars as corrosion resistant alternatives. Several case studies explore the durability and deterioration issues for epoxy-coated bars discovered through 30 years of implementation in reinforced concrete structures. The methods for predicting the end of functional service life for structures reinforced with uncoated reinforcing bars and with epoxy-coated reinforcing bars are detailed and tested in a design problem in the final section of this report.
by Elizabeth Ward-Waller.
M.Eng.
2
Ostrofsky, David. "Effects of corrosion on steel reinforcement." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002258.
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Rylands, Thaabit. "Corrosion of reinforcement in concrete : the effectiveness of organic corrosion inhibitors." Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/9946.
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Includes bibliographical references.Reinforcement corrosion in concrete has presented engineers with the challenge of finding ways of prolonging the service life of structures built in aggressive environments. One method of increasing the durability of concrete in aggressive environments is the use of corrosion inhibitors. In this work, two organic corrosion inhibitors were tested to observe their effectiveness in decreasing the rate of corrosion or delaying the onset of corrosion. One of the inhibitors was a migrating corrosion inhibitor while the other was an admixed inhibitor. The corrosion rate of reinforcement in concrete specimens used in this evaluation, was measured using the Linear Polarisation Resistance method. The performance of the admixed inhibitor was also measured in aqueous phase tests. Results of the tests conducted indicate that the admixed inhibitor does delay the onset of corrosion. The Mel caused short to medium term inhibition when the chloride concentration was less than 1.5%.
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Hassell, Rhett Colin. "Corrosion of rock reinforcement in underground excavations." Thesis, Curtin University, 2008. http://hdl.handle.net/20.500.11937/1247.
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The effect of corrosion on the performance of rock support and reinforcement in Australian underground mines has not been widely researched and is generally not well understood. This is despite the number of safety concerns and operational difficulties created by corrosion in reducing the capacity and life expectancy of ground support. This thesis aims to investigate corrosion and relate how the environmental conditions in Australian underground hard rock mines impact on the service life of rock support and primarily rock reinforcement. Environmental characterisation of underground environments was completed at a number of mine sites located across Australia. This provided an improved understanding of the environmental conditions in Australian underground hard rock mines. Long-term testing on the impact of corrosion on the load bearing capacity of reinforcement and support under controlled experimental conditions was conducted in simulated underground environments. Rock reinforcement elements were examined in-situ by means of overcoring of the installed reinforcement and surrounding rock mass. Laboratory testing of the core determined changes in load transfer properties due to corrosion damage. These investigations provided an excellent understanding of the corrosion processes and mechanisms at work. Corrosion rates for a range of underground environments were established through the direct exposure and evaluation of metallic coupons in underground in-situ and simulated environments.It was found that the study of corrosion is challenging due to the time required to gather meaningful data. In particular, the wide range of materials that comprise ground support systems means that it is impossible to examine all the possible combinations of variables and their potential influence on the observed levels of corrosion and measured corrosion rates. Despite these challenges, the systematic investigation has resulted in new corrosivity classifications for both groundwater and atmospheric driven corrosion processes for various reinforcement and support systems used in the Australian underground mining industry. Previous corrosivity classifications were not found applicable. Furthermore, these new corrosivity classifications are simpler than previous classifications and corrosion rates may be predicted from readily obtained measurements of ground water dissolved oxygen and atmospheric relative humidity. Different types of reinforcement and surface support systems have been rated with respect to their corrosion resistance and estimates have been made for the expected service life for various rates of corrosion.
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Hassell, Rhett Colin. "Corrosion of rock reinforcement in underground excavations." Curtin University of Technology, Western Australian School of Mines, Dept. of Mining Engineering and Surveying, 2008. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=17986.
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The effect of corrosion on the performance of rock support and reinforcement in Australian underground mines has not been widely researched and is generally not well understood. This is despite the number of safety concerns and operational difficulties created by corrosion in reducing the capacity and life expectancy of ground support. This thesis aims to investigate corrosion and relate how the environmental conditions in Australian underground hard rock mines impact on the service life of rock support and primarily rock reinforcement. Environmental characterisation of underground environments was completed at a number of mine sites located across Australia. This provided an improved understanding of the environmental conditions in Australian underground hard rock mines. Long-term testing on the impact of corrosion on the load bearing capacity of reinforcement and support under controlled experimental conditions was conducted in simulated underground environments. Rock reinforcement elements were examined in-situ by means of overcoring of the installed reinforcement and surrounding rock mass. Laboratory testing of the core determined changes in load transfer properties due to corrosion damage. These investigations provided an excellent understanding of the corrosion processes and mechanisms at work. Corrosion rates for a range of underground environments were established through the direct exposure and evaluation of metallic coupons in underground in-situ and simulated environments.It was found that the study of corrosion is challenging due to the time required to gather meaningful data. In particular, the wide range of materials that comprise ground support systems means that it is impossible to examine all the possible combinations of variables and their potential influence on the observed levels of corrosion and measured corrosion rates. Despite these challenges, the systematic investigation has resulted in new corrosivity classifications for both groundwater and atmospheric driven corrosion processes for various reinforcement and support systems used in the Australian underground mining industry. Previous corrosivity classifications were not found applicable. Furthermore, these new corrosivity classifications are simpler than previous classifications and corrosion rates may be predicted from readily obtained measurements of ground water dissolved oxygen and atmospheric relative humidity. Different types of reinforcement and surface support systems have been rated with respect to their corrosion resistance and estimates have been made for the expected service life for various rates of corrosion.
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Palumbo, Nicolino. "Accelerated corrosion testing of steel reinforcement in concrete." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60681.
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In the last few decades, there has been an increasing worldwide problem of deterioration of reinforced concrete structures, caused primarily by the corrosion of the steel reinforcement embedded within the concrete. Several factors can influence the corrosion process in different types of inservice structures. This thesis reviews the basic principles of the reinforcement corrosion. Various protection and rehabilitation schemes that can be undertaken in the repair of deteriorated concrete structures are presented. In particular, three specific types of structures in the Montreal region which have undergone rehabilitation are presented as typical case studies. Additionally, major research work done in the area of reinforcement corrosion over the last twenty years is reviewed.This thesis reports the results of an experimental research program carried out at McGill University dealing with accelerated electrochemical corrosion testing of reinforced concrete. The main objective of this study is to determine the importance and influence of the depth of the concrete cover thickness on the rate of corrosion of steel reinforcement and thereby, on the resistance of concrete. Appropriate conclusions and recommendations regarding the construction variables affecting the corrosion process are brought forth.
These conclusions and recommendations can be summarized.
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Constantinou, Anastasia. "The corrosion of steel reinforcement in carbonated concrete." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362540.
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Holloway, Mark. "Corrosion of steel reinforcement in slag-based concrete." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365811.
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Ing, Matthew. "Detection of reinforcement corrosion by an acoustic technique." Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/8108.
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Corrosion of reinforcing steel is a major serviceability issue with reinforced concrete structures, often resulting in significant section and bond loss. However, current non-destructive diagnostic techniques do not allow corrosion to be reliably detected at the very early stages of the process, before damage to the concrete occurs. This research describes the development of an Acoustic Emission (AE) technique as a practical tool for the early detection of corrosion of reinforcing steel embedded in concrete. The study falls into three main areas: (i) determining the influential material parameters of reinforced concrete that affect the magnitude of the acoustic emissions; (ii) investigating the influence of diurnal and seasonal temperature variations on corrosion rate and thus the rate of acoustic emissions; and (iii) developing a testing and evaluation procedure that combines the findings of the first two stages with existing knowledge about corrosion and deterioration of concrete structures. In the first phase of the research material parameters such as cover thickness, compressive strength and rebar diameter were investigated to ascertain the influence of varying these factors on the magnitude of AE Energy obtained per gram of steel loss. The experimental results confirmed that early age corrosion, verified by internal visual inspection and mass loss measurements, can be detected by AE before any external signs of cracking. Furthermore results show that compressive strength was the primary influential parameter, indicating an exponential, empirical relationship between compressive strength and AE Energy. An increase in temperature usually induces an increase in corrosion activity, which should be measurable using the AE technique. Consequently the influences of seasonal and diurnal temperature variations were investigated to determine their impact on undertaking AE measurements. This phase of the research demonstrated that seasonal variations in temperature impart a negligible influence on measured AE Energy. However measurement of AE Energy per hour followed trends in the diurnal temperature and corrosion rate evolution, these being in a state of constant flux. Therefore AE measurements of corrosion in reinforced concrete are more responsive to a change in temperature, and so corrosion rate, as opposed to a specific and constant corrosion rate. In the final phase practical experience with AE from site trials and laboratory work were coupled with leading research and existing knowledge of corrosion in concrete and structural deterioration, to develop a testing and evaluation procedure for on-site application. This rigorous procedure enables reliable corrosion measurements to be undertaken on reinforced concrete structures using AE technology and enabling an assessment of the rate of corrosion induced damage to be made. As far as the author is aware this is the first site testing procedure for detecting corrosion in reinforced concrete using AE. Future research in this area might involve more site testing with a view to improving accuracy and analysis of on-site data, underpinning the developed procedure.
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De, Rojas Ricardo R. (Ricardo Rafael De Rojas Pando) 1978. "New developments in steel reinforcement protection from corrosion." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8613.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2001.Includes bibliographical references (leaves 55-56).
Due to life-cycle costs considerations, the Federal Highway Administration has required that all their new bridge structures have a service life of more than 75 years. The practical use of adequate concrete cover, low water/cement ratio, and corrosion inhibitors and admixtures are not enough to satisfy this requirement. Corrosion still affects the reinforcing steel through the diffusion of chlorides. The steel reinforcement, the last line of defense, has to be addressed in order to protect reinforced concrete structures from corrosion and thus extend the service life. Today, new cost-effective technology has surfaced to address the problem. Nuovinox Stainless-steel clad reinforcing bars, fusion bonded epoxy (3M Skotchkot 426) and the recent Dual Phase Ferritic Martensitic bars (MMFXI/II steels) have emerged. This study describes each new reinforcement protection technology and compares them through cost, service life, availability and resistance considerations. The comparisons show that stainless-steel clad bars have the advantage over all other new reinforcement types. The fusion bonded epoxy closely followed while the MMFX steel, because of its lack of exposure, came in last. A prudent combination of the standard corrosion protection methods with these new technologies in steel reinforcement can potentially provide a cost-effective service of more than 75 years to a structure.
by Ricardo R. De Rojas.
M.Eng.
11
Du, Yingang. "Effect of reinforcement corrosion on structural concrete ductility." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368516.
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This thesis presents the experimental and analytical results to investigate the effect of corrosion on the mechanical properties of reinforcing bars and concrete beams, with particular reference to their ductility. In the experimental works, specimens were electrochemically corroded, before they were loaded to failure. In the finite element analysis, the corrosion of reinforcement was modelled as either internal pressure or radial expansion around corroded bars. The study indicates that the amount of corrosion to cause cracking at the bar and concrete surfaces almost linearly increased with the bar diameter and ratio of cover to diameter, respectively. No matter whether concrete cover c increased or bar distance S decreased, once the ratio of S / c became less than 2.5, corrosion cracks first propagated internally between the bars and caused delamination. Although corrosion did not alter the shape of force-extension curves substantially, it decreased bar strength and, especially, ductility greatly. Furthermore, although the reductions of strengths were identical, the ductility of bars corroded in concrete decreased more rapidly than that of bare corroded bars. Corrosion decreased beam strength and altered its ductility and failure mode. When the cracking of compressive concrete or the reduction of tensile bar area dominated beam response, corrosion increased beam ductility and caused a beam to fail in a less brittle and even ductile manner. When the deterioration of bond strength or the reduction of steel ductility controlled beam behaviour, however, corrosion decreased beam ductility and led the beam to fail in a less ductile and even brittle manner. There is a concern regarding the ductility of reinforcing bars and under-reinforced beams if the amount of corrosion exceeds 100/0, since bar ultimate strain decreased below the minimum requirements prescribed in the Model Code 90 for situations requiring high ductility.
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Ismail, Mohammad. "Electrochemical chloride extraction to halt corrosion of reinforcement." Thesis, Aston University, 1998. http://publications.aston.ac.uk/14158/.
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This thesis presents results of experiments designed to study the effect of applying electrochemical chloride extraction (ECE) to a range of different hardened cement pastes. Rectangular prism specimens of hydrated cement paste containing sodium chloride at different concentrations were subjected to electrolysis between the embedded steel cathodes and external anodes of activated titanium mesh. The cathodic current density used was in the range of 1 to 5 A/m2 with treatment periods of 4 to 12 weeks. After treatment, the specimens were cut into sections which were subjected to pore-solution expression and analysis in order to determine changes in the distribution of free and total ionic species. The effect of the ECE treatment on the physical and microstructural properties of the cements was studied by using microhardness and MIP techniques. XRD was employed to look at the possibility of ettringite redistribution as a result of the accumulation of soluble sulphate ions in the cement matrix near the cathode during ECE. Remigration of chloride which remains after the ECE treatment and distribution of other ions were studied by analysing specimens which had been stored for several months, after undergoing ECE treatment. The potentials of the steel cathodes were also monitored over the period to detect any changes in their corrosion state. The main findings of this research were as follows: 1, ECE, as applied in this investigation, was capable of removing both free and bound chloride. The removal process occurred relatively quickly and an equilibrium between free and bound chlorides in the specimens was maintained throughout. At the same time, alkali concentrations in the pore solution near the steel cathode increased. The soluble sulphate ionic concentration near the cathode also increased due to the local increase in the pH of the pore solution. 2, ECE caused some changes in physical and microstructural of the cement matrix. However these changes were minimal and in the case of microhardness, the results were highly scattered. Ettringite in the bulk material well away from the cathode was found not to increase significantly with the increase in charge passed.3, Remigration of chloride and other ionic species occurred slowly after cessation of ECE with a resultant gradual increase in the Cl-/OH- ratio around the steel.4, The removal of chloride from blended cements was slower than that from OPC.
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Jean-Louis, Marjorie. "Non-destructive corrosion monitoring of steel reinforcement in concrete." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99770.
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The inadequate and inaccurate application of corrosion monitoring techniques for testing reinforced concrete structures had led to considerable early deterioration of these facilities and has resulted in high restoration and replacement costs. The prospect and diligent use of readily available early damage detection tools for use in regular maintenance of these structures could permit timely interventions for restoration and upkeep.This research program was aimed at determining the effectiveness of selected nondestructive testing methods as reliable indicators of early onset corrosion in steel-reinforced concrete. The methodology analyzed the onset of corrosion in a set of steel reinforcing rebars at a specific depth from the concrete surface, and used the resulting data as a predictor of corrosion activity in other reinforcing bars at different depths.
Two series of tests were conducted: the first series included nine individually reinforced concrete samples with varying cover thicknesses; the second series consisted of nine reinforcing steel bars, distributed equally in concrete specimens at different depths from the concrete cover. All specimens were subjected to accelerated corrosion using methods developed at McGill University to reproduce corrosion of steel rebars in a naturally aggressive environment as closely as possible.
The research results concur with the findings of other research programs, affirming that these monitoring tools are adequate predictors of corrosion. Nonetheless, they lack precision and are unable to track the time to corrosion initiation in structural concrete elements.
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McCarthy, Michael John. "Chloride and carbonation-induced reinforcement corrosion in PFA concrete." Thesis, University of Dundee, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490143.
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Thompson, Robert Ashton. "Assessing Levels of Corrosion on Extracted MSE Wall Reinforcement." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8408.
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The purpose of this study was to extract galvanized steel wire reinforcement coupons from mechanically stabilized earth (MSE) walls along I-15 and determine the rate of corrosion that has taken place since Phase I, which was conducted by Gerber and Billings (2010). The galvanized steel reinforcement analyzed in this study has been in place for 19 to 20 years at the time of extraction. A total of 85 coupons were extracted and laboratory analysis was performed to determine the thickness of remaining zinc galvanization on each coupon. Soil samples were obtained from each one-stage wall extraction location to determine moisture content for correlation with corrosion. After laboratory testing was performed, the measured zinc coating thickness was compared to that determined in Phase I. An average corrosion rate of approximately 0.032 oz/ft²/year has occurred since Phase I. According to the AASHTO (2017) design corrosion rate of 0.35 oz/ft²/year for the first two years and 0.09 oz/ft²/year until the depletion of the zinc, the zinc coating would have been completely depleted after 16 years. Based on the results of laboratory testing, the initial galvanization coating was likely greater than the specified thickness of 2.0 oz/ft² (86 μm). The zinc galvanization is corroding at a slower rate than the AASHTO design rate. The AASHTO design rate for depletion of zinc coating and subsequent corrosion of the steel reinforcement is conservative for the corrosion conditions present in the MSE wall reinforcement coupons tested. The integrity of the steel reinforcement that is currently in place is not likely to be compromised by corrosion.
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Gao, Zhicheng. "Corrosion Damage of Reinforcement Embedded in Reinforced Concrete Slab." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1478174479305336.
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Vaca-Cortés, Enrique. "Corrosion performance of epoxy-coated reinforcement in aggressive environments /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Zemajtis, Jerzy. "Modeling the Time to Corrosion Initiation for Concretes with Mineral Admixtures and/or Corrosion Inhibitors in Chloride-Laden Environments." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30721.
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The application of a mineral admixture, or a corrosion inhibitor, or a combination of both are methods used for the corrosion protection for reinforced concrete bridges. The results of a study on evaluation of corrosion inhibitors from three different manufacturers and of concretes with fly ash, slag cement, and silica fume and a concrete with silica fume and a corrosion inhibitor 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% (w/w) sodium chloride solution. In addition, cover depth measurements from 21 bridge decks and chloride data from 3 bridge decks were used, together with laboratory data, in modeling the service lives of the investigated corrosion protection methods.
The methods used to assess the condition of the specimens included chloride concentration measurements, corrosion potentials, and corrosion rates (3LP). Additionally, visual observations were performed for identification of rust stains and cracking on concrete surfaces.
Modeling the time as a function of probability of the end of functional service life (EFSL) is presented. It has been shown that the distributions of surface chloride concentration, C0, and diffusion coefficient, Dc, are key elements in the model. Model predictions show that the concretes with mineral admixtures provide much better level of protection against moisture and chlorides than the ordinary portland cement concrete alone. Application of a corrosion inhibitor causes an elevation of the chloride threshold resulting in an additional increase in time to EFSL.
More field studies are needed to better estimate distributions of surface chloride concentration and diffusion coefficient of Virginia bridge decks, and to confirm predicted times to EFSL for low permeable (LP) concretes.Ph. D.
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Chinthala, Sai Prasanna Prasanna. "Study of Corrosion Inhibitors for Reinforcement Corrosion of Low Carbon Steel in Simulated Pore Solution." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555601685519345.
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Chadwick, Rennie. "Performance of concrete repair materials as corrosion protection for reinforcement." Thesis, University of Surrey, 1993. http://epubs.surrey.ac.uk/757/.
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Ofori-Darko, Francis Kwame. "Crack frequency and the minimisation of reinforcement corrosion in concrete." Thesis, London South Bank University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310062.
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Nokhasteh, Mohammad-Ali. "Corrosion damaged reinforced concrete beams with debonded tensile span reinforcement." Thesis, University College London (University of London), 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294542.
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Yang, Shangtong. "Concrete crack width under combined reinforcement corrosion and applied load." Thesis, University of Greenwich, 2010. http://gala.gre.ac.uk/7145/.
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For reinforced concrete structures subjected to chlorides, carbon dioxide laden and other aggressive environments, corrosion of the reinforcing steel is seen as a global problem. Maintenance and repairs resulting primarily from premature concrete cracking and spalling have an estimated cost running to $100 billion per annum world-wide. The continual demands for greater load carrying capacity of existing infrastructure only exacerbate the problem. In practice, concrete crack width propagation is seen as one of the most important criteria for design and assessment of the long term serviceability of concrete structures. It is therefore economically beneficial to have a fundamental understanding of the growth of the crack width over time so that better informed decisions can be made regarding the carrying out of any repairs. This research attempts to examine the process of concrete cracking and determine the surface crack width of concrete structures under the combined effects of reinforcement corrosion and applied load in both an analytical and numerical manner. In the analytical method, a model for stiffness reduction of cracked concrete has been derived based on the concept of fracture energy and an analytical solution has been obtained. In the numerical method, an interfacial element has been developed to predict concrete crack width under combined effects based on a cohesive crack model in conjunction with finite element codes. To help accurate prediction of crack width in the numerical method, a realistic constitutive relationship for concrete under direct tension has been obtained from the laboratory experiments. It is concluded in this thesis that both the analytical and numerical methods are one of very few available theoretical methods that can predict with reasonable accuracy concrete crack width of reinforced concrete structures under the combined effects of reinforcement corrosion and applied load. This research focuses on concrete cracking caused by reinforcement corrosion and applied load without considering other factors, e.g., weathering, freeze-thaw and chemical attack. Both methods can be used as a tool to assess the serviceability of corrosion affected concrete infrastructure if reinforcement corrosion and applied load are the main causal factors of concrete cracking. For this type of concrete structures, therefore, scientific information can be provided for asset managers in decision making regarding possible interventions. Timely interventions have the potential to prolong the service life of reinforced concrete structures.
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Khatua, Sourav. "Effect of Accelerated Corrosion on the Bond Strength of Corrosion Resistant Reinforcing Bars Embedded in Concrete." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1513944280521728.
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Collins, William D. "Chemical treatment of corroding steel reinforcement after removal of chloride contaminated concrete." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08182009-040410/.
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Seibert, Peter J. "Galvanic corrosion aspects of stainless and black steel reinforcement in concrete." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0007/MQ36080.pdf.
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Maslehuddin, Mohammed. "The influence of Arabian Gulf environment on mechanisms of reinforcement corrosion." Thesis, Aston University, 1994. http://publications.aston.ac.uk/14300/.
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The reduction in the useful-service life of reinforced concrete construction in the Arabian Gulf is attributed to reinforcement corrosion. While this phenomenon is primarily related to chloride ions, the concomitant pressure of sulfate salts may accelerate the deterioration process. Another factor which might influence reinforcement corrosion is the elevated ambient temperature. While few studies have been conducted to evaluate the individual effect of sulfate contamination and temperature on chloride binding and reinforcement corrosion, the synergistic effect of these factors on concrete durability, viz.-a-viz., reinforcement corrosion, needs to be evaluated. Further, the environmental conditions of the Arabian Gulf are also conducive for accelerated carbonation. However, no data are available on the concomitant effect of chloride-sulfate contamination and elevated temperature on the carbonation behaviour of plain and blended cements. This study was conducted to evaluate the conjoint effect of chloride-sulfate contamination and temperature on the pore solution chemistry and reinforcement corrosion. The effect of chloride-sulfate contamination and elevated temperature on carbonation in plain and blended cements was also investigated. Pore solution extraction and analysis, X-ray diffraction, differential thermal analysis, scanning electron microscopy, DC linear polarization resistance and AC impedance spectroscopy techniques were utilized to study the effect of experimental parameters on chloride binding, reinforcement corrosion and carbonation. The results indicated that the concomitant presence of chloride and sulfate salts and temperature significantly influences the durability performance of concrete by: (i) decreasing the chloride binding, (ii) increasing reinforcement corrosion, and (iii) accelerating the carbonation process. (DX185682)
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Saire, Yanez Julio J. "Morphology and Detection of Corrosion on Stainless Steel Reinforcement in Concrete." Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7922.
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Stainless steel (SS) has emerged as an alternative corrosion-resistant reinforcement in concrete instead of the commonly used carbon steel (CS). The biggest advantage of SS is that it takes more time for corrosion to initiate than for CS. An additional benefit from the use of SS in concrete may be derived from the period after the corrosion started until the concrete structure reaches a limit state. This period is called corrosion propagation stage (CPS) and it has been hardly studied in SS reinforced structures. The duration of this period could be related, among other factors, to the morphology of corrosion of stainless steel in concrete. In some instances, the corrosion detection methods for CS have been used on SS reinforced structures to estimate the corrosion condition. However, there is uncertainty if these methods can detect corrosion in SS reinforced structures properly. This investigation was organized in two parts: literature review and experimental work.
The literature review indicated among other findings that the duration of the CPS of SS’s embedded in concrete may be estimated to be in the order of several decades. High-grade SS’s would have a longer duration of the CPS. The review also indicated that even localized corrosion of SS reinforcement may induce concrete cracking. The literature also suggested that the corrosion detection on SS reinforced concrete may require a combination of conventional methods (half-cell potential) and advanced electrochemical techniques such as Electrochemical Impedance Spectroscopy, Electrochemical noise, etc.
The experimental work focused on further determining whether corrosion of SS in concrete can be detected by methods traditionally used for CS reinforcement, and to what extent localization of corrosion of SS compares with that of CS in concrete. The experiments consisted in accelerated corrosion testing of controlled anodic regions along concrete beams, for which tests were designed and initiated.
Martensitic UNS S41000 SS bars were partially embedded in chloride contaminated concrete (5.84% by weight of cement) to cause active corrosion. AISI 1018 CS was also used for comparison purposes. Traditional half-cell potential measurements on the reinforced concrete specimens were evaluated in comparison to that of advanced electrochemical impedance spectroscopy. Additional concrete resistivity monitoring gave an indication of the degree of the pore structure formation.
The traditional half-cell potential measurements on AISI 1018 CS reinforced concrete specimens appeared to be suitable to estimate the corrosion state of the reinforcement. However, there was uncertainty on the interpretation of the half-cell potential results and thus the corrosion state of UNS S41000 SS reinforced concrete specimens.
Low-dispersion corrosion rates values were found over large areas on SS and CS bars in concrete, but that SS embedded in concrete also seemed to develop instances of corrosion rate peaks. Among other findings, the duration of CPS of CS in concrete was estimated to be in the interval [6-59] years. Assuming that the CPS had been reached, SS specimens in concrete appeared to have a much longer duration of CPS than CS, with an interval [57-253] years. However, this assumption is likely not valid and more work is required to assess the CPS of SS reinforced concrete.
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Cromie, James Alexander. "Modelling the electrochemical rehabilitation of chloride contaminated reinforced concrete bridge structures." Thesis, University of Ulster, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342317.
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Williamson, Joanne. "The influence of concrete cover properties on the effects of reinforcement corrosion." Thesis, University of Birmingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496284.
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Misra, A. "Assessment of adhesion strength and corrosion of reinforcement in concrete patch repairs." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411756.
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Deshapriya, Medagoda Arachchige Ananda. "Role of cement content in determining resistance of concrete to reinforcement corrosion." Thesis, University of Dundee, 2003. https://discovery.dundee.ac.uk/en/studentTheses/c3e5f189-81c2-41b8-9426-d49f28aaecfa.
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Out of all the durability problems related to concrete structures, corrosion of reinforcing steel is the single most serious deteriorating process and this is likely to be more severe in the presence of defects (e. g. cracks)in the concrete surface. The review of published literature shows that at fixed w/c ratio, cement reduction is not detrimental to fresh and hardened concrete properties and may improve performance in some cases. However, cement content variations (in some cases) are relatively small and do not cover an adequate range around the specified minimum cement contents in standards. In addition, insufficient data exist to establish relationships between cement content and resistance of concrete to carbonation-andchloride- induced reinforcement corrosion. Moreover, no data were found on the combined influences of crack width and cement content on resistance of concrete to reinforcement corrosion.Given this background, this study was designed to fill in many areas where information was either inconclusive or not available. The experimental programme, which was carried out in three stages, examined the influence of variation in cement and water contents in equal proportion, Le. at fixed w/c ratio, on the fresh, engineering, permeation, durability properties of concrete and, particularly, resistance of concrete (both cracked and uncracked) to reinforcement corrosion at the limits of specifications and beyond, covering concrete mixes made with a wide range of mix constituents.Stage 1 of the study mainly showed that for a given set of constituents, at fixed w/c ratio, cement (and,therefore, water) reduction below the given minimum cement contents in current specifications did not adversely affect the fresh, engineering, permeation and properties of concrete. Indeed, many concrete properties were improved, particularly with the inclusion limestone filler (with cement reduction)to maintain the mix fines content.Stage 2 indicated that observations noted for permeation properties were not influenced by aggregate or cement type. However, for a given mix, the resistance of concrete to permeation was improved by using lower absorption aggregates and PC / PFA or PC / GGBS, instead of PC. Cement reduction at fixed w/c ratio below the given minimum cement contents in current specifications had a minor adverse effect on the carbonation resistance of concrete, particularly when the fines content was allowed to deplete, and this was not influenced by aggregate or cement type. For a given mix, concrete containing absorption aggregate showed higher resistance to carbonation and that containing PC / PFA or PC / GGBS showed lower resistance Furthermore, the effect of cement type on carbonation was more pronounced than that of cement content. However, cement content had no influence on the carbonation-induced reinforcement corrosion after initiation, regardless of aggregate and cement type. Moreover, the effect of cement content on corrosion rate was insignificant compared to the cement type and the use of PFA or GGBS with PC increased the corrosion rate compared to PC. Cement reduction at fixed w/c ratio below the given minimum cement cement contents in current specifications led to reduction in chloride diffusion and chloride content, particularly with the inclusion of limestone filler to maintain the mix fines content, and this was not affected by aggregate or cement type. Again, for corresponding mixes, concrete made with lower absorption aggregate and PC / PFA or PC / GGBS showed greater chloride resistance. Furthermore, the effect of cement type on chloride diffusion was more pronounced than that of cement content. Reflecting the chloride resistance,cement reduction, particularly with the inclusion of limestone filler to maintain the mix fines content,resistance of concrete to chloride-reinforcement regardless of aggregate and cement type and, for a given mix, PC / PFA or PC / GGBS showed greater resistance compared to PC. Stage 3 showed that for concrete with 0.3 mm surface crack (intersecting) width, cement reduction (below the specified minimum cement contents) at fixed w/c ratio slightly increased the chloride penetration through the cracked zone, but led to negligible influences on the resistance of concrete to chloride-induced reinforcement corrosion. Although there was a little influence of the surface crack (intersecting) width varying from 0.1 to 0.5 mm, on the chloride penetration through the cracked zones (not directly proportional to the width), it had no influence on chloride-induced reinforcement corrosion This study demonstrates that in situations, there is no clear need to specify minimum cement contents and, if specified, their values should be reconsidered. Indeed, the minimum cement content may be an unnecessary restriction on mix design. Furthermore, if a reduced or no minimum cement is specified,attention should be made to specify a minimum fines content appropriately to achieve a closed structure and,consequently, to improve the performance of concrete. Moreover, it is a mistake to pay too much attention to cement content in determining the resistance of concrete to reinforcement corrosion, which is likely to be mainly influenced by cement type.
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Theron, Gavin De Vos. "Effects of reinforcement corrosion on the structural performance of reinforced concrete beams." Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/18238.
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This dissertation is an investigation into the effect of reinforcement corrosion on the structural performance of reinforced concrete beams. Two types of specimens are investigated, the first without any stirrups and the second with stirrups. The specimens were corroded galvanostatically as well as by subjecting them to alternate cycles of wetting and drying with a saline water. An attempt is made at classifying the extent of corrosion of the reinforcing steel and its effects on the concrete. The effect of the corrosion on the structural performance is measured by establishing its effect on the maximum load carrying capacity, the deflections, energy requirements and ductility ratio. The main conclusions made in respect of the effect of reinforcement corrosion are that it causes: a decrease in the load carrying capacity; an increase in the deflections at the equivalent load level; a decrease in the energy requirements to reach the maximum load; and a smoothing of the load-deflection relationship. A limited literature review is also presented to provide background information of corrosion in concrete and general structural behaviour. Guidelines for the development of an analytical model to predict the load carrying capacity of corrosion affected reinforced concrete beams are also given.
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Miller, Tri Huu. "NONDESTRUCTIVE INSPECTION OF CORROSION AND DELAMINATION AT THE CONCRETE-STEEL REINFORCEMENT INTERFACE." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/194077.
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The proposed study explores the feasibility of detecting and quantifying corrosion and delamination (physical separation) at the interface between reinforcing steel bars and concrete using ultrasonic guided waves. The problem of corrosion of the reinforcing steel in structures has increased significantly in recent years. The emergence of this type of concrete deterioration, which was first observed in marine structures and chemical manufacturing plants, coincided with the increased applications of deicing salts (sodium and calcium chlorides) to roads and bridges during winter months in those states where ice and snow are of major concern. Concrete is strengthened by the inclusion of the reinforcement steel such as deformed or corrugated steel bars. Bonding between the two materials plays a vital role in maximizing performance capacity of the structural members. Durability of the structure is of concern when it is exposed to aggressive environments. Corrosion of reinforcing steel has led to premature deterioration of many concrete members before their design life is attained. It is therefore, important to be able to detect and measure the level of corrosion in reinforcing steel or delamination at the interface. The development and implementation of damage detection strategies, and the continuous health assessment of concrete structures then become a matter of utmost importance. The ultimate goal of this research is to develop a nondestructive testing technique to quantify the amount of corrosion in the reinforcing steel. The guided mechanical wave approach has been explored towards the development of such methodology. The use of an embedded ultrasonic network for monitoring corrosion in real structures is feasible due to its simplicity. The ultrasonic waves, specifically cylindrical guided waves can propagate a long distance along the reinforcing steel bars and are found to be sensitive to the interface conditions between steel bars and concrete. Ultrasonic transducers are used to launch and detect cylindrical guided waves along the steel bar.In this dissertation, in-situ corrosion monitoring technique for reinforced concrete is developed based on two methods - 1) variation of signal strength and 2) the time-of-flight (TOF) variations as the corroded member is loaded transversely. This is the first attempt ever to monitor corrosion inside concrete by measuring the change in the time of flight of guided waves along reinforcing bars as the concrete beam is subjected to bending. Advantages of corrosion monitoring by TOF change are discussed in the dissertation.
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Lau, Kingsley. "Corrosion of Epoxy-Coated Reinforcement in Marine Bridges with Locally Deficient Concrete." Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1696.
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Epoxy-coated rebar (ECR) has been used in approximately 300 Florida bridges, in an attempt to control corrosion of the substructure in the splash-evaporation zone. Early severe ECR corrosion was observed in the substructure of several Florida ECR bridges (Group 1) where the substructure was built with permeable concrete of high apparent chloride diffusivity DApp. Other ECR bridges built during the same period and having similar DApp were projected to show corrosion damage starting on the following decade. Examination of several of those bridges (Group 2) confirmed that projection. Other recently examined Florida ECR bridges (Groups 3 and 4) were built with very low to moderate permeability concrete having correspondingly low to moderate DApp values at normally sound concrete locations. Those bridges were projected not to show early corrosion at normal locations and that projection has also been confirmed. However, some incidence of thin structural cracks exists affecting a small fraction of the substructure. Chloride transport there is much faster than through the matrix in otherwise low permeability concrete and work has confirmed that early corrosion can develop there.
A predictive ECR corrosion model was applied that replicated most of the damage function features observed in the field. The model divides the substructure in separate elements with individual chloride exposure, concrete permeability, concrete rebar cover, and extent of ECR coating imperfections. Additionally, a model for projecting impact of preexisting cracking on corrosion damage was developed. The projections indicate that relatively isolated cracking should only create topical concrete damage with reduced maintenance requirements. However, model projections indicated that even though assuming that the incidence of damage is limited to a small region around the crack, if the crack orientation with respect to the rebar were adverse and chloride transport were greatly enhanced (as it could be expected in relatively wide cracks), corrosion damage from localized concrete deficiencies could significantly increase maintenance costs.
Electrochemical Impedance Spectroscopy (EIS) measurements of ECR in extracted cores showed good potential for non destructive characterization of the extent of coating damage. A possible method accounting for frequency dispersion effects in the high frequency response (of importance to assess extent of defects) was introduced.
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McLoughlin, Ian Michael. "Modelling of chlorine and moisture transport in concrete." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323869.
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Elgarf, Mahmoud Sabry Abdelwahhab. "The effect of reinforcement corrosion on the structural performance of concrete flexural members." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2004. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=59721.
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Grattan, S. K. T. "Development of fibre optic sensors for monitoring pH and reinforcement corrosion in concrete." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517287.
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Bernard, Sebastien. "Finite Element Modelling of Reinforced Concrete Beams with Corroded Shear Reinforcement." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/26104.
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This thesis presents a finite element (FE) modelling approach investigating the effects of corroded shear reinforcement on the capacity and behaviour of shear critical reinforced concrete (RC) beams. Shear reinforcement was modelled using a “locally smeared” approach, wherein the shear reinforcement is smeared within a series of plane-stress concrete elements at the specific stirrup location. This was done with the objective of incorporating both the reduction in cross-sectional area due to corrosion and the corresponding expansion of corrosion products build up. Corrosion damage was incorporated through equivalent straining induced by the corrosion build up on the affected surrounding concrete where the concrete cover was treated as a thick-wall cylinder subjected to internal pressure. Strains were introduced in the FE model using fictitious smeared horizontal pre-stressing steel, with a compressive pre-straining level related to the degree of corrosion penetration of the reinforcement. The FE modelling approach was first validated against published test data of shear critical RC beams with and without stirrup corrosion. The proposed modelling approach successfully reproduces the load deformation response as well as the failure mode and cracking patterns of the published experimental tests.
Upon validation of the FE model, the work was extended to a parametric analysis of important shear design variables, such as the shear span-to-depth ratio, beam width and stirrup spacing The FE analyses were carried out for three increasing levels of corrosion (low, moderate and high) applied to affected stirrups within the critical section of the beams and based on steel mass loss (10%, 30% and 50%, respectively).
In general, the results show a reduction in load carrying capacity accompanied by a softening of the load-deformation curves with each increasing level of corrosion. In most of the cases, a reduction in deflection associated to peak loads was also observed for moderate and high levels of corrosion. The impact of the various parameters was studied with respect to strength and deformation, as well as crack angle and mid-height horizontal strain. This was done in an effort to compare FE values to those provided by the CSA A23.3 design equations. The CSA A23.3 shear design equations were compared against FE analysis data in terms of residual shear strength estimation and individual component contributions to shear resistance (i.e., concrete and steel). The comparisons revealed an over conservative estimation for both strength and concrete contributions and an overestimation of the steel contribution. This divergence was attributed to a transition in shear behaviour within the critical section. Based on the progression of the concrete compressive struts with increasing corrosion and predicted crack angle, it was found that stresses in affected sections are redistributed towards adjacent undamaged material. The shear resistance mechanism generally transitioned from typical beam behaviour towards an arching-dominated one. Finally, based on important findings from the literature and the work conducted within this research, important considerations for assessment practice are suggested.
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Du, Qixin. "Finite Element Modelling of Steel/Concrete Bond for Corroded Reinforcement." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/33465.
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Reinforcement corrosion is the most common deterioration problem observed in reinforced concrete (RC) structures located at coastal or cold regions. The corrosion process can impact the performance of these structures by inducing damage on the bonding action between concrete and steel, either by the splitting of the concrete cover due to the volumetric expansion of corrosion products or the lubricant effect at the steel/concrete interface as the corrosion by-products accumulate. The current research aims at investigating corrosion-induced deterioration of bond between steel and concrete through finite element (FE) analysis of the flexural behaviour of corroded RC components. By treating the concrete cover as a thick-wall cylinder subjected to internal pressure, the analytical evaluation of impaired bond capacity is studied first and verified against published bonding tests. Then, the formulation of a numerical model is performed using ABAQUS, wherein a link element to simulate the bond behaviour is formulated and implemented through the ABAQUS user-subroutine (UEL) feature according to the validated analytical model. By introducing corrosion-induced damages, i.e., smaller cross-sectional area of reinforcement, splitting of concrete and bond deterioration, in the FE analyses, the results of the numerical model show good agreement with experimental observations. Upon validation of the analytical and FE models, a parametric investigation is conducted, wherein the effects of concrete strength, dimension of reinforcing bars, properties of oxide products, different corrosion damage mechanisms and the corrosion location along the longitudinal reinforcement on the flexural behaviour of RC beams are studied. The results show that the analytical evaluation for bond degradation is impacted by the selection of the post-cracking material model and the thickness of cover that determine the ‘holding capacity’ after cracking initiation. Also, the density of rust by-products affects the results of the analytical model at high corrosion levels. From the FE model results, it was observed that each damage mechanism due to corrosion contribute to different levels of flexural degradation, although the flexural strength degradation is mainly due to the loss of bonding action. The parametric study also demonstrates that flexural members which have reinforcement corrosion initiated near the supports suffer greater deterioration in flexural capacity than those with damages at mid span. Finally, based on these observations, suggestions for the application of both analytical and numerical models are made.
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Abosrra, L. R. "Corrosion of steel reinforcement in concrete : corrosion of mild steel bars in concrete and its effect on steel-concrete bond strength." Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/5417.
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This thesis reports on the research outcome of corrosion mechanism and corrosion rate of mild steel in different environments (saline, alkaline solutions and concrete media) using potentiodynamic polarization technique. The study also included the effect of corrosion on bond strength between reinforcing steel and concrete using pull-out test. Corrosion of mild steel and 316L stainless steel with different surface conditions in 1, 3 and 5% saline (NaCl + Distilled water) was investigated. Specimens ground with 200 and 600 grit silicon carbide grinding paper as well as 1μm surface finish (polished with 1μm diamond paste) were tested. In case of mild steel specimens, reduction in surface roughness caused increase in corrosion rate, while in 316L stainless steel corrosion rate decreased as the surface roughness improved. Metallographic examination of corroded specimens confirmed breakdown of passive region due to pitting corrosion. Corrosion of mild steel was also investigated in alkaline solution (saturated calcium hydroxide, pH =12.5) contaminated with 1, 3 and 5% saline. A series of corrosion experiments were also conducted to examine the efficiency of various concentrations of calcium nitrite (CN) on corrosion behaviour of both as-received and polished mild steel in alkaline solution containing 3% saline after 1 hour and 28 days of exposure. Corrosion rate was higher for the as-received than polished mild steel surface under the same testing conditions in NaCl alkaline solution with and without nitrites due to the effect of surface roughness. Morphology investigation of mild steel specimens in alkaline solution ii containing chlorides and nitrites showed localized pits even at nitrite concentration equal to chloride concentration. Corrosion of steel bars embedded in concrete having compressive strengths of 20, 30 and 46MPa was also investigated. The effect of 2 and 4% CN by weight of cement on corrosion behaviour of steel bar in low and high concrete strengths specimens were also studied. All reinforced concrete specimens were immersed in 3% saline solution for three different periods of 1, 7 and 15 days. In order to accelerate the chemical reactions, an external current of 0.4A was applied. Corrosion rate was measured by retrieving electrochemical information from polarization tests. Pull-out tests of reinforced concrete specimens were then conducted to assess the corroded steel/concrete bond characteristics. Experimental results showed that corrosion rate of steel bars and bond strength were dependent on concrete strength, amount of CN and acceleration corrosion period. As concrete strength increased from 20 to 46MPa, corrosion rate of embedded steel decreased. First day of corrosion acceleration showed a slight increase in steel/concrete bond strength, whereas severe corrosion due to 7 and 15 days corrosion acceleration significantly reduced steel/concrete bond strength. Addition of only 2% CN did not give corrosion protection for steel reinforcement in concrete with 20MPa strength at long time of exposure. However, the combination of good quality concrete and addition of CN appear to be a desirable approach to reduce the effect of chloride induced corrosion of steel reinforcement. At less time of exposure, specimens without CN showed higher bond strength in both concrete mixes than those with CN. After 7 days of corrosion acceleration, the higher concentration of CN gave higher bond strength in both concrete mixes. The same trend was observed at 15 days of corrosion acceleration except for the specimen with 20MPa compressive strength and 2% CN which recorded the highest deterioration in bond strength.
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Abbas, Ebrahim K. "Corrosion Assessment for Failed Bridge Deck Closure Pour." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/36352.
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Corrosion of reinforcing steel in concrete is a significant problem around the world. In the United States, there are approximately 600,000 bridges. From those bridges 24% are considered structurally deficient or functionally obsolete based on the latest, December 2010, statistic from the Federal Highway Administration (FHWA). Mainly, this is due to chloride attack present in deicing salts which causes the reinforcing steel to corrode. Different solutions have been developed and used in practice to delay and prevent corrosion initiation.
The purpose of this research is to investigate the influence of corrosion on the failure mechanism that occurred on an Interstate 81 bridge deck. After 17 years in service, a 3ft x3ft closure pour section punched through. It was part of the left wheel path of the south bound right lane of the bridge deck. The bridge deck was replaced in 1992 as part of a bridge rehabilitation project, epoxy coated reinforcement were used as the reinforcing steel. Four slabs from the bridge deck, containing the closure, were removed and transported to the Virginia Tech Structures and Materials Research Laboratory for further evaluation. Also, three lab cast slabs were fabricated as part of the assessment program.
Corrosion evaluation and concrete shrinkage characterization were conducted in this research. The corrosion evaluation study included visual observation, clear concrete cover depth, concrete resistivity using single point resistivity, half-cell potential, and linear polarization using the 3LP device. Shrinkage characteristics were conducted on the lab cast slabs only, which consisted of monitoring shrinkage behavior of the specimens for 180 days and comparison of the data with five different shrinkage models. Based on the research results, guidance for assessment of other bridge decks with similar conditions will be constructed to avoid similar types of failures in the future.Master of Science
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Angst, Ueli. "Chloride induced reinforcement corrosion in concrete : Concept of critical chloride content – methods and mechanisms." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for konstruksjonsteknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14245.
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Chloride induced reinforcement corrosion is widely accepted to be the most frequent mechanism causing premature degradation of reinforced concrete structures. Condition assessment and service life prediction is based on comparing the chloride content in the concrete at the steel depth – either measured in the field or computed by means of theoretical modelling – with the chloride content that is believed to be tolerable before corrosion starts. The latter is commonly referred to as critical chloride content or chloride threshold value. Owing to the considerable statistical variation of the parameters involved in service life considerations, probabilistic approaches are preferentially used since these aim at taking into account the uncertainties inherent to all parameters – at least on a theoretical basis. The present thesis approached the issue of chloride induced reinforcement corrosion from various angles. First, a non-destructive chloride measurement technique was studied. Second, the critical chloride content was reviewed with particular focus on how to determine this value experimentally and on common practice of its application. In a third part, the mechanism of chloride induced corrosion was experimentally studied. Regarding the measurement of chlorides, the application of ion selective electrodes (ISEs) as non-destructive chloride sensors in concrete was investigated. It was found that silver / silver chloride electrodes respond to the chloride ion activity in the pore solution as expected from theory and are functional also in highly alkaline environments. However, correct measurement of the sensor potential is the critical step and in this regard, the presence of diffusion potentials was identified as serious error source. These disturbing potentials arise from concentration gradients along the measurement path between reference electrode and ISE, particularly owing to pH gradients and chloride profiles. The error can be minimised by optimal placing of the reference electrode with respect to the ISE. Generally, in uncarbonated, alkaline concrete, the accuracy of this non-destructive chloride measurement method was found to be comparable to the accuracy of common procedures to determine the acid-soluble chloride content in concrete powder. On the other hand, when the pH of the concrete is on a lower level such as owing to the presence of pozzolanas, the adverse effect of diffusion potentials arising from chloride profiles increases and negatively affects the measurement accuracy. A review on the critical chloride content has shown that this parameter scatters significantly in the literature and that the published data does not offer a basis to improve service life predictions. The reported values are not consistent, particularly regarding non-traditional binder types. This was, at least partly, explained by the wide variety of experimental methods and the pronounced effect of certain experimental parameters. It was concluded that there is a strong need for a generally accepted, practice-related test setup for the critical chloride content. Without reliable input data, the common practice of probabilistic service life modelling is highly questionable. Both based on experimental results as well as the literature review, recommendations were made for a realistic test setup; these include the use of ribbed steel in as-received condition, chloride exposure by cyclic wetting and drying as well as leaving the rebar at its free corrosion potential rather than subjecting it to potentiostatic control. While it was from experimental work concluded that even in rather small laboratory specimens, the cathode is sufficiently large to provide realistic conditions for (early) pitting corrosion, probabilistic considerations have illustrated that the specimen size is likely to significantly influence the measured critical chloride content. More specifically, the smaller the specimens, the higher the expected mean critical chloride content and the larger the scatter of measured values. It was further discussed how the size effect influences the concept of critical chloride content and service life modelling in general. It was suggested that the size of specimens on which the critical chloride content is measured has to be taken into account when transferring the values to structures of real-life dimensions in probabilistic service life calculations. A procedure of how this can be done by considering structural behaviour was sketched (characteristic length). Regarding corrosion performance, the steel/concrete interface was found to be the most important influencing factor. Investigations by means of scanning electron microscopy revealed microstructural differences of top and lower sides of rebars that were horizontally orientated during casting, in particular the presence of a bleed-water zone below the reinforcement. It was striking that chloride induced corrosion initiated preferentially on the rebar side with the bleed-water zone regardless of the direction of chloride ingress. Also entrapped air voids were frequently observed at the steel/concrete interface; however, these coincided never with the location of corrosion onset. It was suggested that the internal moisture state is decisive in determining which interfacial defects present a risk of corrosion initiation. Last but not least, it was experimentally observed that steel embedded in concrete might depassivate/repassivate several times until stable pitting corrosion is achieved – at least under unpolarised conditions. After the first signs of corrosion onset, a marked increase in chloride content was often required to prevent repassivation and to enable stable pit growth. The time at which the chloride content is measured and taken as critical chloride content is thus decisive for the outcome of a laboratory test method. It was suggested that in order to obtain practicerelated chloride threshold values, this should be done as soon as stable pit growth is achieved (rather than at the first depassivation event). Finally, measurements after depassivation provided insight into the mechanism of early pitting corrosion and lead to the conclusion that the corrosion kinetics are at this stage dominated by anodic diffusion control.
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Hussein, Mohammed Taj Al-Haj. "The effect of cement type on the potential and corrosion behaviour of steel reinforcement." Thesis, University of Surrey, 2003. http://epubs.surrey.ac.uk/2758/.
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The corrosion of reinforcing steel has emerged as the most prevalent factor causing deterioration of reinforced concrete structures in aggressive exposures, such as the Middle East and Arabian Gulf States. Recently, the effect of using embedded steel bars passing through different types of concrete has been found to exacerbate the corrosion activity. This may occur with a steel bar passing from a foundation manufactured with sulphate resistance Portland cement (SRPC) into a beam or column manufactured with ordinary Portland cement (OPC). This thesis aims at elucidating the behaviour of reinforcing steel (RC) embedded in concrete mixes of different types by incorporating both OPC and SRPC and blends with ground granulated blast furnace slag and pulverised fuel ash. Two different types of RC specimens were used: Single bars in a single mix and electrically connected bars in same or different mix types sharing a common electrolyte in the absence and presence of a specific interface. The RC specimens were exposed to wet-dry cycles of chloride and sulfate solutions. The results of steel bars that were electrically connected, and were embedded in concrete cubes manufactured with different cement types and without a direct interface exhibited reduced times to onset of corrosion when subjected to chloride ion ingress. In the worst case, the connection of the a bar in OPC (0.45) concrete and one in SRPC (0.45) concrete caused the bar in the SRPC (0.45) mix to start corroding after only 3 cycles (6 weeks) compared to 15 cycles (30 weeks) for a single unconnected bar in the same SRPC (0.45) concrete. Moreover, measurements of the half-cell potential, polarisation resistance and corrosion current, all confirm that a single bar passing the interface between two different concretes manufactured with different cement types can suffer the formation of anode and cathode regions that depend on the local environment. For example, a steel bar passing from an OPC (0.45) concrete to a SRPC (0.45) concrete will preferentially form an active anode within the SRPC concrete. This has implications for concrete structures manufactured using SRPC foundations and OPC superstructure, as often used in the Arabian Gulf States
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Bajaj, Srikanth. "Effect of Corrosion on Physical and Mechanical Properties of Reinforced Concrete." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1353961865.
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Brown, Michael Carey. "Corrosion Protection Service Life of Epoxy Coated Reinforcing Steel in Virginia Bridge Decks." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/27690.
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The corrosion protection service life extension provided by epoxy-coated reinforcement (ECR) was determined by comparing ECR and bare bar from 10 bridge decks built between 1981 and 1995. The objective was to determine the corrosion protection service life time extension provided by ECR field specimens with various degrees of coating adhesion: disbonded, partially disbonded, and wholly bonded coatings.
The size and length distributions of cracks in Virginia bridge decks were investigated to assess the frequency and severity of cracks. Correlation of cracks with chloride penetration was used to characterize the influence of cracking on deck deterioration. Cracks influence the rate of chloride penetration, but the frequency and width distributions of cracks indicate that cracks are not likely to shorten the overall service life of most bridge decks in Virginia.
Altogether, 141 drilled cores, 102 mm (4 inches) in diameter, were employed in this study. For each of the decks built with ECR, 10 to 12 cores were drilled through a top reinforcing bar adjacent to the previous study core locations. In addition, approximately 3 cores were drilled through a top reinforcing bar at a surface crack location. Laboratory testing involved nondestructive monitoring using advanced electrochemical techniques to periodically assess the corrosion state of the steel bars during cyclic exposure to chloride-rich solution over 22 months of treatment. Time of corrosion initiation and time of cracking (where applicable), as well as chloride content of the concrete before and after treatment, were used in the analysis.
Less than 25 percent of all Virginia bridge decks built under specifications in place since 1981 is projected to corrode sufficiently to require rehabilitation within 100 years, regardless of bar type. The corrosion service life extension attributable to ECR in bridge decks was found to be approximately 5 years beyond that of bare steel.Ph. D.
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Metaferia, Ineku Amhayesus. "Characterization of Steel Corrosion Products in Reinforced Concrete." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42128.
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Steel corrosion is one of the major distress mechanisms that causes the deterioration of reinforced concrete structures around the world. It is an electrochemical reaction between the reinforcing steel and the surrounding concrete that produces a mass loss of the metal. Through the process of corrosion in reinforced concrete, iron ions get oxidized to form corrosion products (CP). Although multiple experiments and studies have been developed to understand the rheological behavior of corrosion products, this topic stays inconclusive. This work aims to characterize corrosion products at micro-scale in order to trace the progress of the formation of rust, to determine its nature and to analyse its rheological behavior in reinforced concrete. An experimental procedure to produce CP in the laboratory is also presented in this research. In addition, material characterization methods have been used to identify the iron oxide phases present in CP, determine their viscosity and rheological behavior and to study how CP flows in a porous media. In order to identify the different stages in the corrosion process, the CP was analysed at 2, 4, 6 and 8 weeks. The experiments identified four phases of iron oxide for each period. Furthermore, it was found that CP behaves as a shear-thinning slurry and as a result, its viscosity decreases with the applied shear rate. In addition, the damage caused by CP on concrete depends on the w/c ratio of the concrete mix and the exposure time to a corroding environment. The rebar mass loss results show that CP is formed in layers around the rebar, and the flow of each CP layer can differ.
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Baingo, Darek. "A Framework for Stochastic Finite Element Analysis of Reinforced Concrete Beams Affected by Reinforcement Corrosion." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23063.
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Corrosion of reinforcing bars is the major cause of deterioration of reinforced concrete (RC) structures in North America, Europe, the Middle East, and many coastal regions around the world. This deterioration leads to a loss of serviceability and functionality and ultimately affects the structural safety. The objective of this research is to formulate and implement a general stochastic finite element analysis (SFEA) framework for the time-dependent reliability analysis of RC beams with corroding flexural reinforcement. The framework is based on the integration of nonlinear finite element and reliability analyses through an iterative response surface methodology (RSM). Corrosion-induced damage is modelled through the combined effects of gradual loss of the cross-sectional area of the steel reinforcement and the reduction bond between steel and concrete for increasing levels of corrosion. Uncertainties in corrosion rate, material properties, and imposed actions are modelled as random variables. Effective implementation of the framework is achieved by the coupling of commercial finite element and reliability software. Application of the software is demonstrated through a case study of a simply-supported RC girder with tension reinforcement subjected to the effects of uniform (general) corrosion, in which two limit states are considered: (i) a deflection serviceability limit state and (ii) flexural strength ultimate limit state. The results of the case study show that general corrosion leads to a very significant decrease in the reliability of the RC beam both in terms of flexural strength and maximum deflections. The loss of strength and serviceability was shown to be predominantly caused by the loss of bond strength, whereas the gradual reduction of the cross-sectional area of tension reinforcement was found to be insignificant. The load-deflection response is also significantly affected by the deterioration of bond strength (flexural strength and stiffness). The probability of failure at the end of service life, due to the effects of uniform corrosion-induced degradation, is observed to be approximately an order of magnitude higher than in the absence of corrosion. Furthermore, the results suggest that flexural resistance of corroded RC beams is controlled by the anchorage (bond) of the bars and not by the yielding of fully bonded tensile reinforcement at failure. This is significant since the end regions can be severely corroded due to chloride, moisture, and oxygen access at connections and expansion joints. The research strongly suggests that bond damage must be considered in the assessment of the time-dependent reliability of RC beams subjected to general corrosion.
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Simioni, Paola [Verfasser], and Harald [Akademischer Betreuer] Budelmann. "Seismic Response of Reinforced Concrete Structures Affected by Reinforcement Corrosion / Paola Simioni ; Betreuer: Harald Budelmann." Braunschweig : Technische Universität Braunschweig, 2009. http://d-nb.info/117582951X/34.
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Tang, Denglei, and Denglei Tang@gmail com. "Influence of Chloride-induced corrosion cracks on the strength of reinforced concrete." RMIT University. Civil, Environmental and Chemical Engineering, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080530.091350.
Full textAbstract:
In marine environments and where de-icing salts are applied, the degradation of reinforced concrete structures due to chloride induced corrosion of the reinforcement is a major problem. The expansive nature of the corrosion process results in cracking of the concrete and eventually spalling. In order to select suitable remedial measures it is necessary to make an assessment of the residual strength and the residual life. In order to investigate the effect of corrosion on bond strength of the reinforcement, specimens comprising square prismatic sections containing steel reinforcement in the four corners have been subjected to a wet-dry cycle and corrosion has been accelerated by polarising the bars. The research has studied the change of bond strength with level of corrosion for 12 mm and 16 mm bars with concrete cover of 1 and 3 times the bar size. The bond strength is assessed by means of pull out tests and the corresponding extent of corrosion has been assessed in terms of the mass loss. Observations and measurements of the form of the corrosion (pit dimensions and loss of bar diameter) are also presented. The relationship between bond strength and surface crack width has been investigated. Results show that the surface crack width may be a good indicator of residual bond strength. In addition, the influence on bond strength of concrete compressive strength, reinforcement cover, bar position and bar size on the change of bond strength has been explored. It should be noted that all conclusions drawn in this project are based on tests on specimens without shear reinforcement (unconfined) and that accelerated corrosion (by impressed current) has been adopted. Consequently, care should be exercised in applying these results directly to structures in the field. Additional research is needed to assess the influence of impressed current on crack patterns and the effect of shear reinforcement.