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The purpose of this paper was to characterize the surface of steel reinforcement of concrete under cathodic protection (CP), submerged in seawater, to understand the…
The purpose of this paper was to characterize the surface of steel reinforcement of concrete under cathodic protection (CP), submerged in seawater, to understand the surface changes due to the application of CP and their consequences on cathodic current requirements.
Reinforced concrete specimens with applied CP were immersed in natural seawater. The experimental methodology included monitoring of corrosion potential (Ecorr); measurement of galvanic current (Igalv), protection potential (Eprotection) and the depolarization potential of steel during the time of exposure; and electrochemical impedance spectroscopy (EIS). The chemical composition of the steel surface was assessed using X-ray diffraction (XRD).
The application of CP leads to the formation of a deposit on the steel surface that according to XRD results, Pourbaix diagram and physical characteristics, is a protective oxide: magnetite (Fe3O4). This oxide causes a decrease in the corrosion rate and requires application of the protection current. It was found that the surface remained protected even after eight days when the CP system was interrupted.
It is necessary to carry out analysis of the chemical composition of deposits formed on the steel surface, perhaps using X-ray photoelectron spectroscopy, Mössbauer, to verify the presence of the magnetite.
Determination of the main cause of the decrease in current required for protection and deposit formation conditions will enable the design of a CP system to be optimized and economized. At present, the CP design considers only a constant current value for the duration of the protection time.
CP is a technique that has proven effective for the protection of metal structures. However, little attention has been devoted to the surface changes that occur under applied CP and their impact on the electrochemical behavior of the system. This paper describes the phenomena produced at the metal surface and determines kinetic parameters and their consequences on the CP behavior.
The purpose of this paper is to present the results of a two-year long study carried out in order to evaluate the corrosion performance of mild steel bare bars (BB) and…
The purpose of this paper is to present the results of a two-year long study carried out in order to evaluate the corrosion performance of mild steel bare bars (BB) and epoxy-coated rebar (ECR) in concrete under a simulated harsh environment of chlorides.
The blocks are subjected to Southern Exposure testing. The electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and Tafel plot are performed to measure the polarization resistance and corrosion current densities of these rebars. Knife-peel test was performed to assess the adhesion between epoxy and underlying steel after two years of exposure.
Mild steel BB showed a high corrosion current density of 1.24 µA/ cm2 in Tafel plots and a very low polarization resistance of 4.5 kΩ cm2 in LPR technique, whereas very high charge transfer resistance of 1672 and 1675 kΩ cm2 is observed on ECR and ECR with controlled damage (ECRCD), through EIS technique, respectively. EIS is observed to be a suitable tool to detect the defects in epoxy coatings. After two years of immersion in 3.89 percent NaCl− solution, the mild steel BB were severely corroded and a considerable weight loss was observed, whereas under heavy chloride attack, ECR showed no deterioration of epoxy coating and neither any corrosion of underlying steel. Results of this study show that the durability of reinforced concrete (RC) structures with respect to corrosion could be enhanced by using ECR, especially in harsh climatic conditions.
The corrosion performance of mild steel and ECR in concrete under a simulating splash zone environment is evaluated. EIS was used to evaluate the health of epoxy and corrosion state of underneath steel rebars. EIS was able to detect the defects in epoxy. The durability of RC structures could be enhanced in harsh climate regions by using ECR.
Gives a bibliographical review of the finite element methods (FEMs) applied for the linear and nonlinear, static and dynamic analyses of basic structural elements from the…
Gives a bibliographical review of the finite element methods (FEMs) applied for the linear and nonlinear, static and dynamic analyses of basic structural elements from the theoretical as well as practical points of view. The range of applications of FEMs in this area is wide and cannot be presented in a single paper; therefore aims to give the reader an encyclopaedic view on the subject. The bibliography at the end of the paper contains 2,025 references to papers, conference proceedings and theses/dissertations dealing with the analysis of beams, columns, rods, bars, cables, discs, blades, shafts, membranes, plates and shells that were published in 1992‐1995.
3. Unsolved problems and future developments The previous sections may indicate that cathodic protection, at least if installed to the best standard practice, will solve all immersed corrosion problems offshore. This would be incorrect. However, the history of those structures in the North Sea with complete records of effective cathodic protection indicates that the existing techniques do largely result in safe structures for long periods.
Draws on the findings of a major research project funded by the NewSouth Wales Department of School Education in Australia which sought toexamine the school‐community…
Draws on the findings of a major research project funded by the New South Wales Department of School Education in Australia which sought to examine the school‐community interface and communication in government comprehensive high schools in that state. Data were drawn initially from nine schools in Western Sydney with three of these schools being the subject of in‐depth follow‐up study. These studies revealed the significant role played by senior school executives, particularly the principal, in the development of communication methods in schools and their influence on school culture and climate. Examines decision making and communication methods in the three schools within the context of each school′s environment and draws implications for school leadership, staff morale, and staff, student and community attitudes. A key finding is that there is no “recipe” for success as a principal. Rather, a contingency approach is advocated whereby individual principals adopt a personal position across a range of important considerations, these positions being dependent on contextual and personal factors. The case studies suggest what these positions could be.
IT was in September that we asked “What do Bullocks Produce?”. Well, now we know; and a right mess of controversy is the result. Or is it a result or, rather, a cause the result of which may well sound the virtual end of British business as we have known it and it has been built up over the years? It could also sound the death‐knell of the Mother of Parliaments; for power is being given, irrevocably, to the Unions.