Corrosion of reinforcing steel in cracked concrete.
Item
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Title
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Corrosion of reinforcing steel in cracked concrete.
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Identifier
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AAI3325472
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identifier
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3325472
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Creator
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Bi, Mingdong.
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Contributor
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Adviser: Kolluru V. Subramaniam
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Date
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2008
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Civil
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Abstract
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Cracks are often produced in concrete structures due to the action of loads or for other reasons such as restrained shrinkage and thermal movements. Once a crack is formed, it provides an easy and fast access for ingress of ions to the steel surface. A crack in concrete also introduces spatial variations in the concentrations of oxygen and chloride ions at the steel surface, which results in a spatial inhomogeneity in the state of steel along the length of the rebar. Predicting the rate of corrosion of steel in cracked concrete is therefore particularly challenging and conventional electrochemical techniques tend to under-predict the rate of corrosion.;The main objective of this research is to investigate the influence of a crack in concrete on the corrosion of a steel bar. The mechanism of corrosion in a steel bar which is intersected by a crack along its length is investigated using beam specimens. A representation of the macrocell corrosion system, which forms along the length of the steel bar, is developed using an Evans diagram considering the Tafel polarization responses of active and passive steel in concrete. A fundamental relationship between the local microcell and macrocell corrosion rates which result in metal loss at the crack is developed using the Evans diagram representation of the system. An equivalent distributed element circuit model for the system is developed to predict the rate of steel corrosion. The proposed circuit model is shown to provide reasonable prediction of the macrocell corrosion in cracked concrete.;Results of an experimental program investigating the polarization response of steel in cracked concrete are reported. The equivalent circuit model provides favorable prediction of the current distribution in the specimen. An implementation procedure for the proposed circuit model for predicting the rate of corrosion of steel in cracked concrete from a polarization test is developed. A practical approach to obtain the area of anode and the macrocell corrosion rate in the field measurements is presented.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
