Dissertations / Theses on the topic 'Reinforced concrete – Corrosion'
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1
Leyne, Eileen. "Corrosion in reinforced concrete repair." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82611.
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Lack of a scientific design approach for repair and rehabilitation of corroding reinforced concrete infrastructure has resulted in significant financial and social costs. This experimental program was primarily undertaken to examine the corrosion process in reinforced concrete repair, which has different characteristics as compared with corrosion in new construction. The program was designed to gain a deeper understanding of how certain restoration strategies may lead to problems of electrochemical incompatibility and result in ineffective corrosion mitigation.Fifteen specimens, 1m by 1m by 0.2m, were cast to represent a section of a deteriorating reinforced concrete bridge deck slab. The central portion was uniquely designed to simulate the deterioration caused by corrosion activity in a bridge deck slab. After initiating corrosion using wetting and drying cycles with 15% salt solution, each specimen was subjected to a unique restoration strategy. The wetting and drying cycles continued, and a monitoring program was established to observe the corrosion activity of each specimen.
The results corroborate current research, that patch repairs can trigger the formation of a macrocell corrosion cell, or a ring of active corrosion surrounding the repaired zone. In addition, the results from the electrochemical testing revealed sharp differences in the corrosion behaviour of the different restoration strategies. However, the physical evidence of minimal corrosion for all four specimens that were demolished at the end of the testing period, reveals a discrepancy with the electrochemical testing results.
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Katwan, Moufaq Jassem. "Corrosion fatigue of reinforced concrete." Thesis, University of Glasgow, 1988. http://theses.gla.ac.uk/5327/.
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This work is concerned with the corrosion fatigue characteristics of full-scale reinforced concrete beams partially submerged in 3.5% NaCl solution or in tapwater of low dissolved salt content. The test beams were subjected to constant amplitude fatigue loading in uni-directional or reverse bending at slow cycle rate of 0.17 Hz and various load levels. The test programme had two stages: Stage I, carried out at relatively high load levels, represented a study of the fatigue-failure phenomenon but also provided guides for the more detailed study undertaken in Stage II which was devoted to low load conditions under which the main steel deterioration process was corrosion. In the latter stage, attention was focused on the monitoring of a number of electrochemical parameters including the corrosion rate. Late in the programme, electrochemical noise technique was also examined. The phenomenon of concrete crack blocking, previously reported in seawater environment, was observed in both test environments in this work. This phenomenon was closely examined and the mechanisms of the formation of deposits and its effects were described. A hypothesis was proposed for the structural behaviour of reinforced concrete beams during cyclic loading in aqueous environment. Failure normally occurred by the fracture of one of the main tensile bars due to fatigue, often followed immediately by yield of the remaining bar and beams collapse. Fracture surfaces were examined under SEM.Corrosion rate measurements involved formidable difficulties which had to be overcome to obtain accurate measurements. For instance, the current interruption technique for the estimation of the IR-drop was developed and established as the most appropriate method for concrete beams with complex reinforcement configuration. Extensive polarisation measurements indicated clear effect of the test condition on the technical variables involved in various measuring techniques (viz potentiodynamic and potentiostatic techniques). Based on these observations a criterion has been proposed to determine the appropriate variables necessary for the accurate determination of the polarisation resistance Rp. The work has demonstrated that the corrosion behaviour of reinforced concrete sustaining dynamic loading is extremely complex, and short term indications could not be used safely for long term predictions. Based on corrosion rate measurements and the actual corrosion pattern observed upon completion of the tests, a concept of a change in corrosion mechanism from a microcell process of relatively low corrosion rates to a macrocell process at much accelerated high rates is introduced. The prevailing mechanism depends on time of exposure, load level and reinforcement details. Results from long running fatigue tests in seawater from concurrent research were incorporated which also support this concept.
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Saifullah, Mohammad. "Effect of reinforced corrosion on bond strength in reinforced concrete." Thesis, University of Birmingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496283.
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Premature deterioration of reinforced/prestressed concrete structures due to corrosion is of considerable current concern. One detrimental effect of corrosion of reinforcing/prestressing steel is the reduction of bond between steel and concrete due to the development of corrosion products at the interface. This thesis examines the influence of localized corrosion of reinforcing bars/ untensioned prestressing strands on their bond strength in concrete. In addition, an analytical study is conducted in order to investigate the complex behaviour due to cracking of cover concrete, non-uniform corrosion, presence of softened paste layer at the interface between steel and concrete, and stress relaxation due to creep in relation to the bond strength. The conditions of severe localized corrosion were simulated electrochemically. The main variables were cover-to-bar diameter ratio, reinforcement type, and corrosion rate. The influence of reinforcing/prestressing steel corrosion and cracking of the concrete cover on the behaviour of bond were studied at different stages of corrosion: non-corrosion, precracking, cracking, and postcracking levels. It was found that the bond strength increased with corrosion up to a certain amount. However, with the progressive increase in corrosion, the bond strength decreased very rapidly until the cracking of cover concrete, and then decreased at a very slow rate in the postcracking stage. The untensioned prestressing strands showed almost similar general behaviour but were found relatively more deteriorated due to corrosion in the postcracking stage under the similar corrosive conditions. The structural properties of steel such as yield strength and ultimate tensile strength were influenced significantly due to the enormous local reduction in cross-sectional area of the reinforcing/prestressing steel by corrosion. The test data showed that the percentage corrosion required to cause cracking of cover concrete varied linearly with cover-to-bar diameter ratio. Bond-slip studies at different stages of corrosion indicated that bond stiffness increases and then decreases with the increase of corrosion of reinforcing steel in concrete. Corroded prestressing strands exhibited a nonlinear bond-slip relationship. Corrosion rate was found to be a significant variable. Pullout bond specimens using deformed bars were exposed to the current densities of 4.0,2.0, 1.0,0.5,0.25,0.15,0.09, and 0.04 mA/cm'. Bond behaviour was studied at the cracking stage and after 20% corrosion. The results indicated a significant and non-linear effect of corrosion on bond strength. Both corrosion to cause cracking and bond strength as a ratio of the non-corroded bond strength increased with an increase of current density up to about 0.15-0.25 mA/CM2 , and then decreased with a further increase in current density. This explains the different results obtained by previous researchers at different corrosion rates. Finite element analysis of the effect of concrete cover at the stages of internal and surface cracking confirmed the behaviour found in the laboratory study. The presence of an interfacial softened paste layer showed no significant effect on the expansive pressure. The study of the relaxation of stresses due to creep showed that the high degradation in bond strength at high rate of corrosion was significantly contributed by the relaxation of stresses due to creep at the cracking stage. However, in the postcracking stage, creep showed little effect on the stresses in the concrete surrounding the reinforcing bar. It is concluded that it is extremely difficult to extrapolate laboratory data to field conditions. However, a simple assessment rule is proposed.
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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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Stanish, Kyle David. "Corrosion effects on bond strength in reinforced concrete." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq29397.pdf.
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Licardie, Giezi A. "Aggressive chlorine induced corrosion of embedded reinforced concrete /." Available to subscribers only, 2005. http://proquest.umi.com/pqdweb?did=1079666041&sid=2&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Lawson, K. "Corrosion monitoring and protective coating of reinforced concrete." Thesis, University of Manchester, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292460.
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Christodoulou, Christian. "Repair and corrosion management of reinforced concrete structures." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13577.
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The durability of concrete structures is affected by a number of factors such as environmental exposure, electrochemical reactions, mechanical loading, impact damage and others. Of all of these, corrosion of the reinforcement is probably the main cause for the deterioration of steel reinforced concrete (RC) structures. Corrosion management is becoming increasingly necessary as a result of the growing number of ageing infrastructure assets (e.g. bridges, tunnels etc.) and the increased requirement for unplanned maintenance in order to keep these structures operational throughout their design life (and commonly, beyond). The main RC repair, refurbishment and rehabilitation approaches generally employed can be broadly categorised under a) conventional, b) surface treatments, c) electrochemical treatments and d) design solutions. The overarching aim of this research was to identify the key corrosion management techniques and undertake empirical investigations focused on full-scale RC structures to investigate their long-term performance. To achieve this, individual research packages were identified from the above broad five approaches for repair, replacement and rehabilitation. These were 1) Patch repairs and incipient anodes, 2) Impressed Current Cathodic Protection, 3) Galvanic Cathodic Protection and 4) Hydrophobic treatments. The selection of the above research packages was based on past and present use by the construction industry to repair, refurbish and rehabilitate RC structures. Their contributions may be broadly categorised as i) Investigations on how specific treatments and materials perform, ii) Investigations on the effectiveness of existing methods of measurements and developing alternatives, iii) Changes to the existing theory of corrosion initiation and arrest and iv) Changes to management framework strategies. The key findings from each research package can be summarised as follows: Macrocell activity appears to be a consequence rather than a cause of incipient anode formation in repaired concrete structures, as has previously been presented; ICCP has persistent protective effects even after interruption of the protective current; Discrete galvanic anodes installed in the parent concrete surrounding the patch repair are a feasible alternative to galvanic anodes embedded within the patch repairs of RC structures; Silanes may have a residual hydrophobic effect even after 20 years of service.
9
Anstice, D. J. "Corrosion inhibitors for the rehabilitation of reinforced concrete." Thesis, Aston University, 2000. http://publications.aston.ac.uk/14159/.
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Four corrosion inhibitors namely sodium nitrite, sodium monofluorophosphate, ethanolamine and an alkanolamine-based mixture were studied by immersing mild steel bars for 42 days in model electrolytes of varied pH and chloride concentration which were intended to simulate the pore solution phase present within carbonated and/or chloride-contaminated concrete. Site trials were carried out on sodium monofluorophosphate and the alkanolamine-based inhibitor to study their depth of penetration into concrete. The influence of various carbonating atmospheres on the pore solution chemistry and microstructure of hydrated cement paste was investigated. Physical realkalisation of carbonated cement paste and a calcium nitrite-based corrosion rehabilitation system for chloride-contaminated cement paste were investigated by monitoring ionic transport within the pore solution phase of laboratory specimens. The main findings were as follows: 1,Sodium nitrite, sodium monofluorophosphate, ethanolamine and the alkanolamine-based mixture all behaved as passivating anodic inhibitors of steel corrosion in air-saturated aqueous solutions of varied pH and chloride concentration. 2,Sodium monofluorophosphate failed to penetrate significantly into partially carbonated site concrete when applied as recommended by the supplier. Phosphate and fluoride penetrated 5mm into partially carbonated site concrete treated with sodium monofluorophosphate. 3,The ethanolamine component of the alkanolamine-based inhibitor was found to have penetrated significant depths into partially carbonated site concrete. 4,Carbonating hydrated cement paste over saturated solutions of sodium nitrite resulted in significant concentrations of nitrite in the pore solution of the carbonated paste. Saturated solutions of sodium chloride, ammonium nitrate, magnesium nitrate and sodium dichromate were investigated and identified as alternatives for controlling the relative humidity of the carbonating environment. 5,Hardened carbonated cement paste can by physically realkalised to a limited extent due to the diffusion of hydroxyl ions under saturated conditions. A substantial proportion of the hydroxyl ions that diffused into the carbonated cement paste however, became bound into the cement matrix. Hydroxyl ion concentrations remained below 5mmol/l within the pore solution of the realkalised cement paste. 6, Nitrite ions penetrated significant distances by diffusion within the pore solution of saturated uncarbonated hydrated cement paste.
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Milman, Ioulia. "CFRP wraps for corrosion repair of reinforced concrete columns and corrosion monitoring." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58671.pdf.
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Hristova, Roumiana. "Evaluation of corrosion inhibitors in chloride-contaminated reinforced concrete." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/10389.
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The report describes research to determine the effectiveness of commercial corrosion-inhibiting admixtures on the corrosion of reinforcing steel in chloride contaminated concrete. Domestic and foreign publications were reviewed to locate performance data and current practices related to the use, testing and evaluation of corrosion inhibiting admixtures. The study consisted of identification and evaluation of the currently used corrosion-inhibiting admixtures in the United States and other countries. A list of available corrosion-inhibiting admixtures were appraised. Consideration was given to performance predictability, practicality, cost, and other pertinent factors. Five-year old "lollipop" concrete speciments containing sodium nitrite and dinitrobenzoic acid as corrosion inhibitors, and comparison with control specimens were studied using linear polarization and impedance spectroscopy. All mixes had different amounts of calcium chloride added. An equivalent circuit model considering the physical characteristics of the rebar/concrete interface was used to simulate the impedance spectra. The RC parameters obtained from the impedance simulation, including maximum phase angle shift, surface impedance and capacitive responses, were utilized to characterize the surface corrosion of embedded steel and to evaluate the effect of inhibitors with chloride content. The corrosion current densities determined by impedance measurement were compared with those determined using linear polarization and good agreement between the two methods was obtained.
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Sun, Jianhui. "Probabilistic analysis of reinforced concrete bridge girders under corrosion." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0004/MQ42210.pdf.
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Ji, Chen Hui 1967. "Design of reinforced concrete elements for durability against corrosion." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80112.
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The main objective of this research is to establish durability design models for flexural concrete elements subjected to a given aggressive environment. Because corrosion of reinforcement due to chloride ingress is the most significant threat to an existing reinforced concrete structure such as a road bridge or a harbor facility which is exposed to chloride-rich environments, corrosion due to chloride ingress is emphasized in this research. The concrete beams can get corroded to different corrosion levels. Mass loss of the reinforcement is an important parameter, and it can help define the corrosion level, and this information can be used to develop a correlation between corrosion, cracking, bond strength at the steel-concrete interface, and the ultimate strength of the reinforced concrete elements. Therefore, the prediction model of reinforcement mass loss under different levels of chloride concentration needs to be established first using the principles of corrosion electrochemistry. Secondly, design development length is determined based on the mass loss prediction and bond strength equation. Thirdly, the model for the prediction of flexural capacity of reinforced concrete beam for a given design service life is established. Some examples of practical durability design are presented. Finally, a step-by-step durability design procedure is recommended for use by practicing engineers. (Abstract shortened by UMI.)
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Brown, Michael Carey. "Assessment of Commercial Corrosion Inhibiting Admixtures for Reinforced Concrete." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/36386.
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Corrosion of reinforcing steel in concrete exposed to chloride-laden environments is a well-known and documented phenomenon. The need for cost effective systems for protection against corrosion has become increasingly clear since the first observations of severe corrosion damage to interstate bridges in the 1960's. As one potential solution to the mounting problem of corrosion deterioration of structures, corrosion-inhibiting admixtures have been researched and introduced into service.
This report conveys the results of a three-part laboratory study of corrosion inhibiting admixtures in concrete. The commercial corrosion inhibiting admixtures for concrete have been analyzed by three evaluation methods, including:
* Conventional concrete corrosion cell prisms under ponding,
* Black steel reinforcing bars immersed in simulated concrete pore solutions,
* Electrochemical screening tests of special carbon steel specimens in electrochemical corrosion cells containing filtered cement slurry solution.
The purposes of the study include:
* Determining the influence of a series of commercially available corrosion inhibiting admixtures on general concrete handling, performance and durability properties not related to corrosion.
* Determining the effectiveness of corrosion inhibiting admixtures for reduction or prevention of corrosion of reinforcing steel in concrete, relative to untreated systems, under laboratory conditions.
* Conducting a short-term pore solution immersion test for inhibitor performance and relating the results to those of the more conventional long-term corrosion monitoring techniques that employ admixtures in reinforced concrete prisms.
* Determining whether instantaneous electrochemical techniques can be applied in screening potential inhibitor admixtures.
Concrete properties under test included air content, slump, heat of hydration, compressive strength, and electrical indication of chloride permeability. Monitoring of concrete prism specimens included macro-cell corrosion current, mixed-cell corrosion activity as indicated by linear polarization, and ancillary temperature, relative humidity, and chloride concentration documentation. Simulated pore solution specimens were analyzed on the basis of weight loss and surface area corroded as a function of chloride exposure. Electrochemical screening involved polarization resistance of steel in solution. Results include corrosion potential, polarization resistance and corrosion current density.Master of Science
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Penumatsa, Gowtham Penumatsa. "Corrosion Detection in Reinforced Concrete Using Acoustic Emission Technique." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1462898129.
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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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Chen, Liquan. "Steel corrosion sensing and chloride control in concrete structures /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202008%20CHEN.
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Thistlethwaite, Christopher. "Behaviour of massive reinforced concrete sections in seawater." Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/4819cd1e-a5ce-48c2-a982-874196b3e8d9.
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This study combined research available through literature with extensive experimental studies and substantial physical modelling to estimate the remaining ultimate life of large offshore reinforced concrete structures. Although much research has focussed on concrete degradation due to chloride ingress, corrosion of permanently submerged concrete is regarded as negligible due to the long-assumed apparent worst case of tidal or splash zone exposure. Around 350 specimens were tested with a further 200 exposed for further testing by future research groups. Specimens ranged in size from standard cubes to various beam lengths up to 1.5 metres, allowing for material and structural properties to be assessed. My original contribution to knowledge in the sector enhances the fundamental understanding of corrosion in subsea concrete, challenging the generally held belief of negligible corrosion. Results and modelling provides an improved ability to ultimately estimate the longevity of fully submerged offshore reinforced concrete. Throughout this thesis, the results from experimental works, carried out as a direct result of the lack of data or information in literature, are reported, assessed and then utilised to provide updated ultimate life estimations. With the current offshore concrete structures currently coming to the end of their service life, and the likelihood of further offshore development using concrete for the renewables sector, understanding the long-term degradation is vital in determining the most effective decommissioning and derogation options. The research carried out directly provides detailed information of the likely time-to-failure, allowing for an informed decision to be made on operational and decommissioning plans. Experimental work was carried out over four main phases; corrosion initiation due to bulk diffusion of chlorides (Phase I), corrosion propagation in low oxygen environments (Phase II), corrosion in statically and dynamically cracked sections (Phase III) and structural response of heavily corroded individual and lapped bar sections (Phase IV). Phase I work shows a marked difference between submerged exposures to seawater as opposed to NaCl solution, the unsuitability for accelerated testing with seawater and the likelihood of rapid initiation in offshore structures. Further experimental works through Phases II and III found that although exposed to low oxygen concentrations, reinforcement corrosion continued at significant rates. A variation between anode sizes on the reinforcement is noted, but critically the cross sectional area of the steel was still reduced, albeit in fewer locations. Corrosive products were visibly different, with fewer expansive products, if any, present. Additionally, this study further highlights the importance of cracking on corrosion, currently ignored by recent model codes, such as the fib Model Code 2010, up to 0.2mm crack width. A linear relationship was found between crack width and corrosion rates, with cracking above 0.1mm considered significant. The loss of cross sectional area due to propagation was determined for the given environment, and consequently further studies were initiated in an attempt to determine the relationship between this corrosion propagation and the reduced serviceability or ultimate life of concrete beams. Serviceability, defined by beam stiffness, was reduced due to bond loss along reinforcement. Most importantly, however, results prove that the loss of cross sectional area to be the critical influence on loss of ultimate life. Initial estimates on the remaining ultimate life of the large offshore structures support early rough work that the structures would last centuries. This thesis, however, has shown this is due to the ability of concrete structures with such large volumes of steel to continue to ultimately withstand loading at high corrosion percentages and not due to negligible corrosion, or long initiation periods, commonly suggested in submerged, low oxygen environments.
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Busba, Ezeddin Rafaa. "Effect of Localized Corrosion of Steel on Chloride-Induced Concrete Cover Cracking in Reinforced Concrete Structures." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4872.
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Abstract: Concrete cover cracking due to reinforcement corrosion is widely accepted as a limit-state indicator in defining the end of functional service life for existing reinforced concrete (RC) structures undergoing corrosion. Many of the currently available durability prediction models are incapable of providing realistic estimates of remaining service lives of RC structures beyond the corrosion initiation point. Therefore, the need to incorporate the length of the corrosion propagation stage in a comprehensive durability prediction approach has recently received much research attention. Previous research focus however was mostly limited to the case of uniformly corroding reinforcement with only few studies addressing the commonly encountered case of localized rebar corrosion. It was empirically shown in a previous study that localized corrosion can have a mitigating effect on time to concrete cover cracking due to the larger required depth of rebar corrosion penetration (Critical penetration or Xcrit). The present research was focused on developing a model for predicting Xcrit for various degrees of corrosion localization including new cases of highly localized corrosion. Accelerated corrosion testing of controlled anodic regions along axial rebars in sound concrete cylinders suggested that localized corrosion can increase Xcrit by up to about a factor of 10. The effect of corrosion localization on the orientation of corrosion-induced surface cracks was also addressed. Testing of freely corroding pre-cracked RC pipe specimens in a chloride-containing environment indicated that steel corrosion can be localized at intersection regions with the pre-existing cracks and uniformly distributed around the reinforcing steel perimeter. Numerical modeling was undertaken to substantiate the experimentally observed trends on a theoretical basis for various degrees of corrosion localization. A mechanical model was developed to improve understanding of the underlying mechanism responsible for corrosion-induced stresses. A thick-walled multiple-cylinder approach was employed to simulate crack initiation and propagation to account for the residual strength property of concrete after cracking by applying the principles of applied elasticity. For a given concrete cover depth, the amount of Xcrit was shown by modeling to be largely determined by the length of corroding region and the capacity of the induced cracks to accommodate produced rusts. The properties of both concrete-rebar interface and corrosion products were also found to have a significant impact on Xcrit. Based on the model and experimental trends and comparisons with literature data, an improved relationship for the estimation of Xcrit was proposed. An electrochemical model was also formulated to address the possible role of corrosion aggravation due to macrocell coupling in counteracting the mitigating effect of increased Xcrit on time to concrete cover cracking. Findings confirmed that corrosion localization can reasonably be considered a mitigating factor for extending the corrosion propagation stage, and provided more precise quantification to that effect.
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Gurusamy, K. "The marine durability of steel fibre reinforced concrete." Thesis, University of Aberdeen, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234802.
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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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Oleiwi, H. M. "Using cathodic protection to control corrosion of reinforced concrete structures." Thesis, University of Salford, 2018. http://usir.salford.ac.uk/47895/.
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Cathodic protection (CP) has been increasingly used on reinforced concrete structures to protect steel reinforcement from corrosion. However, due to the complexity of environmental conditions, the specifications in national and international standards are still open to discussion in engineering practices for their accurate suitability. To some extent, the design aspects are still based on practical experience. It implies a great deal of estimations and assumptions. The research conducted in the thesis aims to address some of these challenges. To obtain reliable experimental results, the present study at first investigated the influence of experimental methods on the measurement of concrete electrical resistivity. It studied the effect of alternative current (AC) frequency, electrode materials and electrode configuration. Based on the results, an optimised method was decided for all the series of the experimental tests in this study. The CP study consists of two major works. The first one was to investigate the chloride contaminated concrete exposed to atmospheric condition. Impressed constant current method was adopted for the operation of CP. A series of electrical and electrochemical measurements were conducted for concrete resistivity, corrosion potential, corrosion rate, degree of polarization, instant-off potential and four-hour potential decay. An evaluation on the current adopted criterion in standards has been carried out on the experimental results. The second work was to investigate the corrosion of rebar in concrete specimens submerged (fully and partially) in salty water. For such more corrosive environment, a comparison between the impressed CP operation using constant current and that using constant potential has been conducted. The experiments evaluated the effects of the two major environmental factors, i.e. water and chloride contents, on reinforced concrete durability. The work provided a deep understanding on the electrochemical behaviour of the reinforced concrete system and effectiveness of CP implementation under severe conditions. The research work has an important contribution to fundamental science of corrosion and reinforced concrete deterioration, and the technology and practical application of CP for reinforced concrete structures. The main results of this work indicate the important influence of the frequency and electrode configuration on the electrical resistance measurement. For the reliability of electrical resistivity measurement, a high frequency of 10,000 Hz and an internal carbon fibre electrode method are recommended. Regarding the CP for the chloride contaminated reinforced concrete exposed to the atmosphere, it is suggested that adopting an instant-off potential of -500 mV with respect to Ag/AgCl/0.5KCl reference electrode can provide sufficient protection for the reinforced concrete of up to 0.59 % total chloride by weight of concrete, or concrete resistivity is greater than 6.7 kΩ.cm. Furthermore, it was found that the 100 mV depolarization criterion for the evaluation of CP performance gives an overestimated protection. A depolarization of 50 mV is therefore proposed. In terms of the submerged specimens, the results showed that the water content and chloride content should be explicitly related to the corrosion state rather than through a single parameter of the concrete resistivity for the complicated situations because the water content will affect the oxygen transportation in concrete, and the oxygen availability at the rebar surface will play an important role in the corrosion process, and this is unassessable by concrete resistivity. Moreover, 4 or 24 hours for the 100 mV depolarisation criterion in standards is not applicable for CP assessment where concrete structures are fully submerged due to the low availability of oxygen. On the other hand, the depolarization criterion can be used if the specimens are partially submerged, but different parameters affect the depolarization value such as the magnitude of the applied protection current or potential, chloride concentration, oxygen availability and time of depolarization.
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Lewis, Jeremy D. "The Effects of Corrosion on Reinforced Concrete with Fiber Addition." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1355171708.
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LU, LIHENG. "Experimental Study of Reinforced Concrete Ties under Load and Corrosion." Doctoral thesis, Politecnico di Torino, 2012. http://hdl.handle.net/11583/2497132.
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Corrosion of reinforcing bars embedded in concrete is a worldwide problem that affects numerous reinforced concrete (RC) structures, which generates expansive products and decreases the cross section of the bars, compromising the safety of the structure. In Italy, the national highway network comprises a large number of reinforced concrete bridges whose service life exceeded 40 years. The cost of maintenance and replacement for these highway bridges due to corrosion damage is measured in billions of euros. In this study, the major aim is the experimental research on two sets of reinforced concrete elements subjected to load and corrosion, the following work is done:
Problem statement, corrosion mechanisms of steel in concrete, the deterioration effects in reinforced concrete subjected to corrosion, and the influence of corrosion on structural performance are summarized firstly. Then, the previous experimental studies and effects of various parameters on bond strength, flexural strength, shear strength and column behavior of reinforced concrete specimens are discussed. After that, the design and results of experimental tests on reinforced concrete ties subjected to: cyclic loading, cyclic loading and simultaneous corrosion, static loading and corrosion, are described and discussed. An electrochemical corrosion process is used for the accelerated corrosion tests; the geometry of specimens and the loading procedure that reproduces the usual conditions for bridge elements under fatigue loading are presented. During the tests both transversal cracks evolution and longitudinal crack formation for corroded specimens are monitored.
Test results confirm that the main effect of crack opening evolution is due to the interaction between corrosion and cyclic loading. Crack opening value is directly related to the bond between steel and concrete and so the previous results can be considered as findings about bond performance. The formation of longitudinal cracking caused by corrosion and its evolution, determined also from the loading condition were monitored. It can be assumed as an indicator of the corrosion level affecting rebars. Finally those observations underline the importance of a coupled mechanical and chemical test for a reliable evaluation of performance for structure under loading and corrosion.
Keywords: reinforcement corrosion, cyclic loading, crack opening, structural damage
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Heiyantuduwa, Rukshani. "Performance of a penetrating corrosion inhibitor in controlling carbonation induced corrosion in reinforced concrete." Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/11581.
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Includes bibliography.Reinforcement corrosion in concrete remains the most serious cause of premature deterioration of concrete structures world-wide, and many methods have been proposed to combat this problem. One method of improving the durability of concrete in aggressive environments is the use of corrosion inhibitors. In this work the effectiveness of an organic penetrating corrosion inhibitor in reducing the rate of corrosion and delaying the onset of corrosion in carbonated concrete is discussed, with reference to corrosion rates.
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Yan, Fei. "GFRP Bars in Concrete toward Corrosion-free RC Structures: Bond Behavior, Characterization, and Long-term Durability Prediction." Diss., North Dakota State University, 2016. http://hdl.handle.net/10365/25864.
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Corrosion of steel reinforcements is the leading causes of malfunction or even failures of reinforced concrete (RC) structures nationwide and worldwide for many decades. This arises up to substantial economic burden on repairs and rehabilitations to maintain and extend their service life of those RC public projects. The inherent natures of glass fiber-reinforced polymers (GFRP) bars, from their superior corrosion resistance to high strength-to-weight ratio, have promoted their acceptance as a viable alternative for steel reinforcement in civil infrastructures. Comprehensive understanding of the bond between GFRP bars and concrete, in particular under in-service conditions or extremely severe events, enables scientists and engineers to provide their proper design, assessment and long-term predictions, and ultimately to implement them toward the corrosion-free concrete products. This research aims to develop a holistic framework through an experimental, analytical and numerical study to gain deep understanding of the bond mechanism, behavior, and its long-term durability under harsh environments. The bond behavior and failure modes of GFRP bar to concrete are investigated through the accelerated aging tests with various environmental conditions, including alkaline and/or saline solutions, freezing-thawing cycles. The damage evolution of the bond is formulated from Damage Mechanics, while detailed procedures using the Arrhenius law and time shift factor approach are developed to predict the long-term bond degradation over time. Besides, the machine learning techniques of the artificial neural network integrated with the genetic algorithm are used for bond strength prediction and anchorage reliability assessment. Clearly, test data allow further calibration and verification of the analytical models and the finite element simulation. Bond damage evolution using the secant modulus of the bond-slip curves could effectively evaluate the interface degradation against slip and further identify critical factors that affect the bond design and assessment under the limit states. Long-term prediction reveals that the moisture content and elevated temperature could impact the material degradation of GFRP bars, thereby affecting their service life. In addition, the new attempt of the Data-to-Information concept using the machine learning techniques could yield valuable insight into the bond strength prediction and anchorage reliability analysis for their applications in RC structures.ND NASA EPCoR (FAR0023941)
ND NSF EPSCoR (FAR0022364)
US DOT (FAR0025913)
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Gastebled, Olivier J. "Fracture in reinforced concrete : computational and analytical studies." Thesis, Heriot-Watt University, 1999. http://hdl.handle.net/10399/1238.
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Volpi, E. "MICROBIAL INDUCED REINFORCED CONCRETE DETERIORATION AND INNOVATIVE PROTECTION TECHNIQUES." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/333048.
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Reinforced concrete deterioration due to steel reinforcing bars corrosion is recognized as a serious problem, affecting the durability of various types of civil structures. Many efforts have been dedicated to studying the steel corrosion process induced by chloride penetration, being by far the most frequent cause for reduced durability of reinforced concrete structures. Much less attention has been focused on the microbial degradation of reinforced concrete structures occurring as a consequence of the presence of bacteria involved in the sulfur cycle (Sulfate Reducing Bacteria and Sulphur Oxidizing Bacteria) whose metabolic products react with the cementitious matrix yielding to fast deterioration processes. According to literature, in such field, most of the attentions were focused on concrete deterioration, while if and how bacteria metabolites eventually affect the behaviour of the steel reinforcing bars appears to be still an open issue.
The research project aims at filling up the knowledge gap above mentioned, that is: assessing how risky and aggressive a bacterial environment is, especially focusing on corrosion of steel reinforcing bars. On this purpose, abiotic solutions, simulating bacteria metabolic products were used for all tests. While a second part of the work was devoted to the development of a "smart" inhibitive system able to protect steel rebars from the corrosion induced by biogenic acidity that slowly neutralize cement alkalinity. The prolonged protective effect was meant to be achieved by encapsulating the active substances into pH sensitive microbeads, that would release the inhibitor only when reached by the acidification front, thus preventing a premature leaching of the inhibitor.
As a common practice in concrete science, investigations were started from the easier system of the steel rebars directly immersed into simulating solutions. Thus, a stable passive layer was growth on the steel surfaces by means of a three days immersion into a saturated Ca(OH)2 solution. Afterwards, samples were moved into sulfides containing alkaline solutions or diluted sulfuric acid, aiming to simulate the metabolic products of SRB and SOB respectively.
The acidic conditioning, into diluted sulfuric acid solutions, easily dissolved the passive layer and caused a fast onset of generalized corrosion, whose extension was found to be dependent on the acid concentration as indicated by both gravimetric and electrochemical tests. Conversely, sulfides were proven to induced localized corrosion, their interactions with the steel surface resulted to be significantly affected by the pH of the environment. Actually, for a prevailing of hydroxyl ions over the sulfides ones the steel surface remained protected by the oxide layer, while at lower pH steel-sulfides interaction were promoted, yielding to a porous, conductive, and thus non protective layer of iron sulfides.
Once clarified the corrosion mechanisms for steel directly immersed in simulating solutions, reinforced mortar samples were cast, cured, carbonated and then conditioned into two different model media: a sulfides containing solution and diluted sulfuric acid solution. The combination of several electrochemical techniques such as OCP, LPR and EIS pointed out the active behavior of the embedded steel rebars. Visual inspection performed at the end of a 500 days conditioning period confirmed that the acidic conditioning yielded to more severe damages.
On the basis of such findings, a "smart" corrosion inhibitor was developed by combining together calcium phosphate and methylene blue dye, being both active compounds in terms of protection of carbon steel from sulfuric acid corrosion. The resulting product was an organic/inorganic hybrid where the organic molecules were entrapped into a porous inorganic matrix, granting their release as a function of a pH drop leading to the dissolution of the latter. Anodic and cathodic potentiodynamic polarizations performed in sulfuric acid solution and in presence of the hybrid inhibitor confirmed that both the anodic and the cathodic processes were hindered as a consequence of the combined effect of methylene blue dye and phosphate ions. The effectiveness of the slow release mechanism was evaluated by means of LPR and EIS monitoring by comparing the responses of the hybrid, its two components singularly used and the free corroding system as a control case. The effect of the organic inhibitor was that of significantly increasing the polarization resistance. Such effect was rapidly lost in the case of methylene blue dye alone, while its slow release, together with the synergic effect of phosphate ions contributed to the prolongation of the protective effect.
Finally the interactions of the hybrid and its components with the cementitious matrix were investigated by means of isothermal calorimetry and standard compressive strength tests. The response of both the hydration rate and the strength evolution were found to be independent from the chemical admixtures.
Once excluded the onset of negative side effects, reinforced mortar samples containing different amount of the unloaded HAP and the hybrid MBD-HAP were cast and exposed to a sulfuric acid environment for about four months. However such a conditioning period proved not to be long enough to induce the corrosion of the steel reinforcing bars.
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Phanasgaonkar, Alka 1956. "Diffusion and protection mechanisms of migratory corrosion inhibitors in reinforced concrete." Monash University, Dept. of Materials Engineering, 2000. http://arrow.monash.edu.au/hdl/1959.1/9200.
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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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Lee, Cathy. "Accelerated corrosion and repair of reinforced concrete columns using CFRP sheets." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0005/MQ34118.pdf.
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Dugarte, Margareth. "Polarization of Galvanic Point Anodes for Corrosion Prevention in Reinforced Concrete." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3466.
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The polarization performance of two types of commercial galvanic point anodes for protection of reinforced steel around patch repairs was investigated. Experiments included measurement of the polarization history of the anode under constant current impressed by galvanostatic circuits and in reinforced concrete slabs. The tests revealed, for both types of anodes, a potential-current function (PF) indicating relatively little anodic polarization from an open circuit potential at low current levels, followed by an abrupt increase in potential as the current approached an apparent terminal value. Aging of the anodes was manifested by a continually decreasing current output in the concrete tests, and by increasingly more positive potentials in the galvanostatic tests. Those changes reflected an evolution of the PF generally toward more positive open circuit potentials and, more importantly, to the onset of elevated polarized potentials at increasingly lower current levels. There was considerable variability among the performance of replicate units of a given anode type. Modest to poor steel polarization levels were achieved in the test yard slabs. Modeling of a generic patch configuration was implemented with a one-dimensional approximation. The model calculated the throwing distance that could be achieved by a given number of anodes per unit perimeter of the patch, concrete thickness, concrete resistivity, amount of steel and amount of polarization needed for cathodic prevention. The model projections and aging information suggest that anode performance in likely application scenarios may seriously degrade after only a few years of operation, even if a relatively optimistic 100 mV corrosion prevention criterion were assumed. Less conservative criteria have been proposed in the literature but are yet to be substantiated. Other investigations suggest a significantly more conservative corrosion prevention may apply instead. The latter case would question the ability of the point anodes to provide adequate corrosion prevention.
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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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Kubo, Junichiro. "Methods of remedial treatment for carbonation-induced corrosion of reinforced concrete." Thesis, University of Leeds, 2007. http://etheses.whiterose.ac.uk/277/.
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The importance of carbonation-induced corrosion has grown in recent years owing to the increasing age of reinforced concrete structures. Among the various remedial treatments for the alleviation of the deterioration process, applications of corrosion inhibitors and surface coatings are highlighted in this thesis owing to their ease of practical application to such structures as railway viaducts. The factors that may enhance the effectiveness of the above two methods in terms of retardation of embedded steel corrosion have investigated as follows: (1) Electrochemical injection of corrosion inhibitors into concrete and (2) Fatigue resistance of surface coatings. (1) After the concentration threshold of electrolytes of three organic base corrosion inhibitors, namely ethanolamine, guanidine, and arginine, required for steel passivation had been investigated by steel immersion tests, the inhibitors were injected into fully/partially carbonated cement-based materials from external electrolytes under the influence of an electrical field. The penetrations of the three inhibitors into the embedded steel cathode were satisfactory in terms of steel inhibition. The field-induced penetration was markedly affected by the pK. values of the inhibitors and the pore solution pH. When the electrochemical treatment was applied to partially carbonated cementitious materials, adequate accumulation of the inhibitors was also attained at the cathode for steel passivation; however, the migration of cationic inhibitors was found to be discouraged in the carbonated region by the lowered current densities effectively applied to this region owing to its large resistivity. Mathematical modelling was performed for simulation of the proposed electrochemical inhibitor injection. A model based on the Nernst-Planck equation, taking account of dissociation equilibria and solubility products of the relevant species, and activity coefficient of molecules, yielded a reasonable agreement with the experimental data. In the application of this model to the 2-D cases, representing the domain with a resistor network that could simulate the current distribution within the material resulted in good prediction of concentrations of the species observed in the experiments. The long-term effectiveness of the electrochemical inhibitor injection was monitored for a reasonably long period, whilst the treated concrete specimens were exposed to cyclic wet/dry conditions. As a result, the injected corrosion inhibitors were found to be effective in promoting steel passivation, and ethanolamine showed the best performance with the smallest steel corrosion rates observed during the experiment. (2) For the investigation of properties of surface coatings affecting their long-term fatigue resistance, fatigue tests with a total of 18 million cycles were carried out under varied temperatures for several coatings bridging a substrate crack whose properties( width and dynamic amplitude) were determined by on-site survey methods. It was found that the thickness and the composition are two important properties of surface coatings that significantly influenced their long-term durability when they were exposed to varied environmental temperatures.
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Wang, Yikuan. "Ultrasonic Monitoring of Corrosion in Reinforced Concrete with Top-Bar Defects." Thesis, Curtin University, 2021. http://hdl.handle.net/20.500.11937/88256.
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Top-bar defects in reinforced concrete are voids that are observed below the reinforcing bars that are at an elevation of more than 300 mm, which reduces the bond strength and accelerates the corrosion process of reinforced concrete. Ultrasonic wave-based non-destructive methods have been developed to (i) detect the top-bar effect in reinforced concrete and (ii) discern and monitor the corrosion process in reinforced concrete with and without the top-bar effects.
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Zhong, Jian Zhong. "Development of test methods for assessment of chloride diffusion resistance of surface treatment on concrete." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267130.
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Liu, Youping. "Modeling the Time-to Corrosion Cracking of the Cover Concrete in Chloride Contaminated Reinforced Concrete Structures." Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/30541.
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Significant factors on steel corrosion in chloride contaminated reinforced concrete and time-to-corrosion cracking were investigated in this study. Sixty specimens were designed with seven admixed chloride contents, three concrete cover depths, two reinforcing steel bar diameters, two exposure conditions, and a typical concrete with water to cement ratio of 0.45. Corrosion current density (corrosion rate), corrosion potential, ohmic resistance of concrete and temperature were measured monthly on these specimens using both the 3LP and Gecor devices. Metal loss measurements were performed in accordance with ASTM G1-90, method C3.5, after specimens cracked. The actual corrosion weight loss of the steel reinforcing bars was then compared to the result obtained from the corrosion rate measurement devices. An interaction model for characterizing the dynamic corrosion process was developed based on the five-year corrosion database. The model demonstrates that the corrosion rate is a function of chloride content, temperature at reinforcement depth, ohmic resistance of concrete, and corrosion time after initiation. A time-to-corrosion cracking model was suggested based on a corrosion-cracking conceptual model and critical mass of corrosion products. The model predicted times to corrosion cracking are in good agreement with the observed times to corrosion cracking of the cover concrete.Ph. D.
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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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Wong, Ha Hang Aaron. "Buckling and stability of slender reinforced concrete deep beams." Thesis, University of Newcastle Upon Tyne, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279763.
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Balakumaran, Soundar Sriram G. "Influence of Bridge Deck Concrete Parameters on the Reinforcing Steel Corrosion." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/32665.
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Chloride induced corrosion of steel in concrete is one of the major forms of deterioration mechanisms found in reinforced concrete bridges. Early age corrosion damage reduces the lifespan of the bridges, which results in heavy economic losses. Research has been conducted to identify economic solutions for significantly delaying and/or preventing corrosion damage. Considering the amount of steel reinforcement used in bridge decks, the influence of as constructed parameters including clear spacing between top and bottom reinforcement bars, ratio of cathode to anode areas, and presence of stay-in-place forms on corrosion activity needs to be evaluated.
The influence of the as constructed parameters have been studied using different corrosion assessment methods including resistivity, half-cell potential, linear polarization, chloride content, moisture content, and visual inspection. This study included the clear spacing distances between the anode and cathode of 51, 76, and 102 mm (2, 3, and 4-inch), number of cathodes as 1 and 2, and the presence and absence of stay-in-place forms. Data up to 15 months were taken from a previous study by Smolinski and integrated into the current study period of 35 to 45 months. A trend line may be established to illustrate the changes which took place over the missing time period, from approximately 15 to 35 months, since the specimens were maintained in controlled environment.
Analysis of the data showed that there is a significant difference between the spacing values (2, 3, and 4-inch) through all forms of evaluations. Regarding the other parameters, no significant difference was identified. Variations in resistivity with increasing spacing, even when the water-cement ratio was kept at 0.50, maybe the result of the difference in unit consolidation between the clear spacing specimens. Thus, the corrosion mechanism observed in this study may be resistivity-controlled. Also, autopsy showed that corrosion on the top bars was in general agreement with the measured corrosion activity. The bottom bars had no visible corrosion and the chloride had not penetrated to the bottom bars, regardless of the separation distance between the top and bottom bars. For this laboratory study, the measurements showed that macrocell corrosion influence on the total corrosion was insignificant.Master of Science
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El-Nemr, Amr Maher. "Serviceability of concrete members reinforced with FRP bars." Thèse, Université de Sherbrooke, 2013. http://hdl.handle.net/11143/6124.
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La détérioration des infrastructures au Canada due à la corrosion des armatures est l'un des défis majeurs de l'industrie de la construction. Les progrès récents dans la technologie des polymères ont conduit au développement d'une nouvelle génération de barres d'armature à base de fibres renforcées de polymères (PRF), (en particulier les fibres de verre). Ces barres, résistant à la corrosion, ont montré un grand potentiel d'utilisation pour mieux protéger les infrastructures en béton armé contre les effets dévastateurs de la corrosion. Avec la publication du nouveau code S807-10 "Spécifications pour les polymères renforcés de fibres" et la production de barres en PRF de très haute qualité, celles-ci représentent une alternative réaliste et rentable par rapport à l'armature en acier pour les structures en béton soumises à de sévères conditions environnementales. La conception des éléments en béton armé de barres en PRF est généralement gouvernée par l'état de service plutôt que l'état ultime. Par conséquent, il est nécessaire d'analyser les performances en flexion et le comportement en service en termes de déflexion et de largeur de fissures des éléments en PRF sous charges de service et de vérifier que ces éléments rencontrent les limites des codes. Aussi, de récents développements dans l'industrie des PRF ont conduit à l'introduction des barres en PRF avec des configurations de surface et des propriétés mécaniques différentes. Ces développements sont susceptibles d'affecter leur performance d'adhérence et, par conséquent, la largeur des fissures dans les éléments en PRF. Cependant, les codes de conception et les guidelines de calcul fournissent une valeur unique pour le coefficient d'adhérence (k[indice inférieur b]) en tenant compte des configurations de surface et en négligeant le type de barre en PRF, le diamètre de la barre, et le type de béton et de sa résistance. En outre, le code canadien S807-10 "Spécifications pour les polymères renforcés de fibres" fournit une étape en classant les barres en PRF par rapport à leur module d'élasticité (E[indices inférieurs frp]). Ces classifications ont été divisées en trois classes : Classe I (E[indices inférieurs frp]<50 GPa), Classe II (50 GPa [plus petit ou égal] E[indices inférieurs frp]< 60 GPa) et Classe III (E[indices inférieurs frp] [plus grand ou égal] 60 GPa). Ce programme de recherche vise à étudier expérimentalement le comportement en flexion des éléments en béton en service armé avec différents paramètres sous charges statiques. Le programme expérimental est basé sous plusieurs paramètres, dont les différents ratios de renforcement, différents types de barres (différentes classes comme classifiées par le CAN/CSA S807-10), le diamètre et la surface de la barre, la configuration ainsi que la résistance du béton. De plus, les recommandations actuelles de design pour les valeurs de k[indice inférieur b] et la vérification de la dépendance des valeurs de k[indice inférieur b] sur le type de barres (verre ou carbone), le diamètre des barres et le type de béton et sa résistance ont été étudiées. Le programme expérimental comprenait la fabrication et les essais sur 33 poutres à grande échelle, simplement appuyées et mesurant 4250 mm de long, 200 mm de large et 400 mm de hauteur. Vingt et sept poutres en béton ont été renforcées avec des barres en PRF à base de verre, quatre poutres en béton ont été renforcées avec des barres de PRF à base de carbone, et deux poutres ont été renforcées avec des barres en acier. Toutes les poutres ont été testées en flexion quatre points sur une portée libre de 3750 mm. Les paramètres d'essai étaient: le type de renforcement, le pourcentage d'armature, le diamètre des barres, configurations de surface et la résistance du béton. Les résultats de ces essais ont été présentés et discutés en termes de résistance du béton, de déflection, de la largeur des fissures, de déformations dans le béton et l'armature, de résistance en flexion et de mode de rupture. Dans les trois articles présentés dans cette thèse, le comportement en flexion et la performance des poutres renforcées de barres en PRFV et fabriquées avec un béton normal et un béton à haute performance ont été investigués, ainsi que les différentes classes de barres en PRFV et leurs configurations de surface. Les conclusions des investigations expérimentales et analytiques contribuent à l'évaluation des équations de prédiction de la déflection et des largeurs de fissures dans les codes de béton armé de PRF, pour prédire l'état de service des éléments en béton renforcés de PRF (déflection et largeur de fissures). En outre, à la lumière des résultats expérimentaux de cette étude, les équations de service (déflection et largeur des fissures) incorporées dans les codes et guidelines de design [ACI 440.1R-06, 2006; ISIS Manual No.3, 2007; CAN/CSA-S6.1S1, 2010; CAN/CSA-S806, 2012] ont été optimisées. En outre, les largeurs de fissures mesurées et les déformations ont été utilisées pour évaluer les valeurs courantes de k[indice inférieur b] fournies par les codes et les guidelines de calcul des PRF. En outre, les conclusions ne prennent pas en charge la valeur unique de k[indice inférieur b] pour les barres en PRF de types différents (carbone et verre) avec des configurations de surface similaires et s'est avéré être dépendant du diamètre de la barre.
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Zhao, Li. "SPATIAL RELIABILITY ANALYSIS FOR CORRODED REINFORCED CONCRETE STRUCTURES." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1479123930240399.
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Adiyastuti, Sri Murti Civil & Environmental Engineering Faculty of Engineering UNSW. "Influence of cracks on chloride induced corrosion in reinforced concrete flexural members." Awarded by:University of New South Wales. School of Civil and Environmental Engineering, 2005. http://handle.unsw.edu.au/1959.4/31878.
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The penetration of chloride ions plays a crucial role in reinforcement corrosion and affects the durability and service life of marine structures. The problem is even more acute once cracking occurs in a concrete member. The presence of cracks is shown to have a significant impact on chloride penetration into concrete. It has been recognized, for concrete cracked in flexure, the chloride diffusion coefficient in the tension zone is higher than that in the compression zone. Even a single crack in the tensile zone could contribute to a higher diffusion coefficient compared to that of uncracked members. In this study, the influence of flexural cracks on chloride ion penetration into reinforced concrete beams has been investigated experimentally and a two-dimensional theoretical model is developed. The experimental study investigated the influence of multiple flexural cracks on the chloride diffusivity of reinforced concrete beams and on the corrosion rate of reinforcing bars. The size of the reinforced concrete beams tested is 200 x 250 x 2200 mm with 20mm concrete cover. The beams were pre-cracked using a compression testing machine and the crack widths induced were maintained between 0.1 mm to 0.2 mm. The chloride profile was determined after 1 month, 1 year and 2 years of immersion in 3.0% NaCl solution. The measured chloride profiles of the beams with multiple cracks are compared to those obtained from the uncracked (control) beam. An observation was also made on the effect of cracks on the corrosion development of steel bar after two years of immersion in salt solution. Chloride concentration varied linearly with the depth of crack (at crack planes). A twodimensional model using finite element analysis is developed to evaluate the chloride penetration into cracked concrete. This model was used to verify the chloride penetration data which is obtained from the experimental results. The prediction of chloride ingress, using the two dimensional model agrees well with the short-term and long-term chloride profiles.
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Schokker, A. J. "Improving corrosion resistance of post-tensioned substructures emphasizing high performance grouts /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Prowell, Brian D. "The evaluation of corrosion inhibitors for the repair and rehabilitation of reinforced concrete bridge components." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-09292009-020105/.
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Graeff, Ângela Gaio. "Avaliação experimental e modelagem dos efeitos estruturais da propagação da corrosão em elementos de concreto armado." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2007. http://hdl.handle.net/10183/10389.
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O concreto armado era tido, quando da sua concepção inicial, como um material que teria boa durabilidade e uma vida útil elevada, praticamente dispensando reparos. Com a intensificação de seu uso, todavia, começaram a serem observados diversos processos de deterioração que resultaram, nos casos mais críticos, em severos comprometimentos de desempenho ou falhas prematuras. Dentre as manifestações patológicas que mais transtorno e prejuízos causam às estruturas civis, destaca-se a corrosão de armaduras, por sua elevada incidência e potencial de dano. Embora já exista um considerável número de pesquisas acerca deste tema, percebe-se que a ênfase atual se encontra no estudo do processo de iniciação da corrosão, e poucos estudos se voltam para a caracterização da fase de propagação, onde os danos se intensificam. Assim, esta pesquisa tem a finalidade, pela realização de experimentos conjugados com uma análise numérica, de contribuir para que sejam entendidos os efeitos, em termos de prejuízo do desempenho estrutural, da propagação da corrosão em estruturas civis. Para fins desta pesquisa, consideraram-se como efeitos significativos nas propriedades estruturais: a perda da aderência entre o aço e o concreto; a diminuição da área de seção transversal da armadura; a diminuição da resistência à tração do aço; e o aparecimento de tensões de tração devido ao acúmulo dos produtos de corrosão junto às barras. Foi estimulado o desenvolvimento de processos de corrosão em corpos-de-prova de concreto contendo barras de aço, que usa aplicação de corrente constante e exposição a uma solução de cloretos, e os graus de corrosão estudados foram equivalentes a perdas de massa de 0, 2, 5, 10 e 20%. Os resultados obtidos nesta fase experimental foram empregados como referência para uma análise numérica, cuja validação foi feita pela avaliação de vigas moldadas e deterioradas em laboratório pelo processo de corrosão induzido. Os resultados da pesquisa mostram, em suma, que os corpos-de-prova de concreto afetados pela corrosão de armaduras, devido ao ataque por cloretos, com pequenas perdas de massa (da ordem de 2 e 5%) não apresentam danos significativos nas propriedades estruturais, enquanto que nos corpos-de-prova contaminados com graus de corrosão maiores que 10% estes danos são mais evidenciados, e neste caso as estruturas devem ser obrigatoriamente tratadas ou recuperadas nos casos mais críticos.When reinforced concrete was designed, it was believed to be a material with good durability and great life-cycle, with almost no repairs necessary. With its use intensification, however, it started to be noticed several deterioration processes and, in the most critical cases, these deterioration processes severely compromised the structure performance or leaded to early fails. Among the pathological manifestations which cause more damages to civil structures, it is possible to highlight the reinforcement corrosion due to its great incidence and damage potential. Despite the great amount of researches concerning this issue, the up-to-date emphasis is based on the corrosion initiation process study, and fewer studies focus on the propagation phase characterization, in which damages are intensified. This research aims, trough experimental and numerical analysis, to contribute for a better understanding of the effects, regarding structural performance damage, of corrosion propagation in civil structures. In this research it is considered as important effects on structural proprieties: losses of bond between steel and concrete; the bar cross section reduction; the bar tensile strength reduction; and the development of tension efforts due to rust near the bars. It was stimulated the development of corrosion process in concrete specimens with rebars, which uses constant current impression and chloride solution exposition to accelerate the corrosive process, and the corrosion levels studied were equivalent to bar weight losses of 0, 2, 5, 10 and 20%. The results from this experimental phase were used as reference to numerical analysis, and validated by beams which were cast and deteriorated in laboratory due to inducted corrosion process. The research results show, in a few words, that concrete specimens affected by reinforcement corrosion, due to chloride attack, with low levels of mass losses (approximately 2 and 5%) do not present significant structural properties damages, while in the specimens with corrosion levels higher then 10% these damages are more exposed, and in this case the structures should be obligatory treated or recovered in the most critical cases.
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Tian, Xiaoping. "Modeling reinforced concrete cracking due to corrosion with a fracture mechanics approach." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27300.
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With the increasing need of developing service life models for corrosion-induced damage in reinforced concrete structures, there has been a movement to model the concrete cover as a thick-wall cylinder subjected to an internal pressure due to corrosion products accumulation on the reinforcing steel. These models allow determining the amount of corrosion product necessary to initiate and propagate cracks along the cover. The first generation of models assume that concrete behaves linearly elastic and that the concrete cover does not have any residual tensile capacity once the tensile strength of the concrete has been reached. More advanced models include the softening behaviour of concrete beyond cracking initiation. This thesis proposes such a model wherein the state stress of the concrete cover due to accumulation of corrosion products is determined by analyzing an equivalent thick-wall cylinder subjected to a uniform internal pressure. Concrete is assumed to be an isotropic material, and deformations due to Poisson's ratio are ignored. To describe the behaviour of concrete in the softening region, a linear relation of stress versus displacement and a constant strain field are assumed. Mathematical expressions that determine the state of stress due to corrosion build-up at any point in the concrete cover are obtained by integrating the softening equations along the concrete cover. Analytical models for cracking initiation as well as longitudinal cracking of the concrete cover are formulated for both unconfined and confined conditions. The latter are the result of the presence of shear stirrups or tie/spiral reinforcement. To determine the validity of these models, their results are compared to published experimental data and finite element analyses. Finally, a parameterc analysis using the models is carried out in order to establish the role of significant model parameters on the resulting state of stress of the concrete cover and the associated damage.
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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.
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Hackl, Jürgen. "Generic Framework for Stochastic Modeling of Reinforced Concrete Deterioration Caused by Corrosion." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for konstruksjonsteknikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23861.
Full textAbstract:
Reinforced concrete structures constitute an important fraction of the building infrastructure. This infrastructure is aging and a large number of structures will exceed the prescribed service period in the next decades. The aging of concrete structures is often accompanied by correspondent deterioration mechanisms. One of the major deterioration mechanisms is the corrosion of the reinforcing steel, caused by chloride ions or carbon dioxide exposure.The decisions, made in connection to possible repair or renewals of these structures, have major implications on safety and cost efficiency in a societal dimension. Public authorities, entitled to administrate the infrastructure, are in need of schemes and methodologies that facilitate the optimal management of the already existing stock of structures, especially in regard to repair and maintenance planning.In this thesis a generic framework for a stochastic modeling of reinforced concrete deterioration caused by corrosion is presented. This framework couples existing probabilistic models for chloride and carbonation initiation with models for the propagation and the effects of corrosion. For this purpose, a combination of structural reliability analysis and Bayesian networks is used for the reliability assessment of the reinforced concrete structure.This approach allows to compute probabilities of rare events for complex structures in an efficient way to update the model with new information from measurements, monitoring and inspection results.This framework enables, for the first time, a holistic view of the current service life models, with corresponding sensitivity studies and finding optimal decisions for treating deteriorated reinforced concrete structures. The temporal evolvement of structures can also be represented and analyzed within this framework.
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Sajedi, Siavash. "RELIABILITY-BASED DESIGN OPTIMIZATION OF CORROSION MANAGEMENT STRATEGIES FOR REINFORCED CONCRETE STRUCTURES." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1503333406583485.
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