• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.361-366
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• 2002

The deterioration of concrete structure due to corrosion of the reinforcement has created big financial losses on the overall industries. The volume expansion of the corrosion products causes internal pressure to concrete wall around reinforcing bar. If the maximum principal stress induced by internal pressure exceeds the tensile strength of the concrete at any point of time, a crack forms at any point of material. Therefore, in terms of life assessment of concrete structure, it is very important to predict the amount of corrosion products which induces initial concrete cracking. With this objective, this paper proposes the critical amount of corrosion products at interface between reinforcement and concrete using finite element analysis. If an actual survey of corrosion rates could be made, the model might supply information for condition assessment of existing concrete structure. As the mechanical properties of corrosion product and instantaneous geometry of corroded steel are considered in the analysis, the value obtained will be more realistic.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.235-240
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• 1997

The purpose of this experiment is to verify processing crack direction and state by the corrosion of electrifying re-bar in the salt water. The result of this experiment is the fact that the first crack appear on the surface of water-because of supplying of oxygen and water. The crack processing is on a surface to be contacted by air and to bottom as mainly the vertical direction from a surface of water. The crack by corrosion of steel reinforcing is emerged by the inside of concrete rather than surface concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.1061-1066
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• 2003

Chloride penetration into concrete is the main cause of the steel corrosion in concrete structures exposed to chloride-rich environments. Protective surface coatings are increasingly being applied to concrete structures to reduce chloride penetration. In this study, the performance of various surface coatings was evaluated. Most coatings showed good results for the various tests of the performance evaluation. Surface coatings can delay deterioration such as chloride-induced reinforcing bar corrosion effectively.

• Smart Structures and Systems
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• v.13 no.1
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• pp.41-53
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• 2014

Optical fiber Brillouin sensor in a coil winding setup is proposed in this paper to measure the expansion deformation of a concrete column with a central rebar subjected to accelerated corrosion. The optical sensor monitored the whole dynamic corrosion process from initial deformation to final cracking. Experimental results show that Brillouin Optical Time Domain Reflectometer (BOTDR) can accurately measure the strain values and identify the crack locations of the simulated reinforced concrete (RC) column. A theoretical model is used to calculate the RC corrosion expansive pressure and crack length. The results indicate that the measured strain and cracking history revealed the development of the steel bar corrosion inside the simulated RC column.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.62-65
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• 2003

In this study, to confirm corrosion of reinforced concrete affected by carbonation, chloride ion diffusion, absorption ratio, air permeability, measured carbonation velocity coefficient, chloride ion diffusion coefficient, absorption coefficient, air permeability coefficient. Corrosion velocity under environment of complex deterioration. And than compared corrosion velocity with these coefficients. As the results of this study, the correlation coefficient between chloride ion diffusion coefficients and absorption coefficient was revealed that it is very high. As well, an increase in carbonation, chloride ion diffusion also increases corrosion velocity. It showed that corrosion velocity was affected by the carbonation, chloride ion diffusion, absorption ratio, air permeability. Generally, data on the development of these coefficient made with none, organic B, organic A, inorganic B, and inorganic A is shown. It showed that coating of surface prevent steel bar from deteriorating.

• Magazine of the Korea Concrete Institute
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• v.4 no.2
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• pp.75-81
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• 1992

염분을 함유한 철근콘크리트중의 철근부식에 관한 2년 촉진시험으로부터 콘크리트표면에서 측정한 자연전위값과 실제의 철근 부식상황과를 비교한 결과 철근의 수식상황을 자연전위법을 이용하여 비파괴적으로 진단하는 방법이 유효함을 알았다. 포화칼로멜전극을 사용했을 경우 -300mV이하이면 부식이 발생하였으며 -200mV이상이면 부식이 발생하지 않았다. 또한 부시공시체에 대한 휨강도시험도 행하였으며 중성화에 대한 검토로 행하였다.

• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.785-793
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• 2007

An electrochemical transient response technique was used to study the corrosion of reinforcing steel bar in the concrete. Analysis of the transient electrochemical potential response in a corrosion interface to an applied current has enabled the separate components that make up the measured transient response to be isolated. These components display a range of resistances and capacitances, dependent on the corrosion conditions of the reinforcing steel, which may be attributed to the corrosion process, to effects within the concrete cover or to film effects on the surface of the concrete. In this technique, the corrosion rate was evaluated by summing all of the resistances in the separate components to obtain an aggregated corrosion resistance. However, it is possible that not all resistances identified are associated with the corrosion process. The results obtained show that the corrosion rates are significant dependent on the assignment of the separate components to either corrosion or to other processes. The assignment of resistive components associated with the corrosion rate can be clearly identified by taking a series of the transient measurement at different lateral distances from the corroding reinforcing steel. An inappropriate selection of measurement time however may result in an additional resistance, which is not associated with corrosion, being included or part of the resistance associated with corrosion being left out.

• Structural Engineering and Mechanics
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• v.61 no.6
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• pp.693-700
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• 2017

Concrete cover cracking due to the corrosion of steel reinforcing bars is one of the main causes of deterioration in Reinforced Concrete (RC) structures. The oxidation level of the bars causes varying levels of expansion. The rebar expansions could lead to through-thickness cracking of the concrete cover, where depending on the cracking characteristics, the service life of the structures would be affected. In this paper, the effect of geometrical and material parameters, i.e., concrete cover thickness, reinforcing bar diameter, and concrete tensile strength, on the required pressure for concrete cover cracking due to corrosion has been investigated through detailed numerical simulations. ABAQUS finite element software is employed as a modeling platform where the concrete cracking is simulated by means of eXtended Finite Element Method (XFEM). The accuracy of the numerical simulations is verified by comparing the numerical results with experimental data obtained from the literature. Using a previously proposed empirical equation and the numerical model, the time from corrosion initiation to the cover cracking is predicted and then compared to the respective experimental data. Finally, a parametric study is undertaken to determine the optimum ratio of the rebar diameter to the reinforcing bars spacing in order to avoid concrete cover delamination.

• Computers and Concrete
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• v.22 no.1
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• pp.53-62
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• 2018

Cracking of concrete cover induced by reinforcement corrosion is a critical issue for life-cycle design and maintenance of reinforced concrete structures. However, the critical degree of corrosion, based on when the concrete surface cracks, is usually hard to predict accurately due to the heterogeneity inherent in concrete. To investigate the influence of concrete heterogeneity, a modified rigid-body-spring model, which could generate concrete sections with randomly distributed coarse aggregates, has been developed to study the corrosion-induced cracking process of the concrete cover and the corresponding critical degree of corrosion. In this model, concrete is assumed to be a three-phase composite composed of coarse aggregate, mortar and an interfacial transition zone (ITZ), and the uniform corrosion of a steel bar is simulated by applying uniform radial displacement. Once the relationship between radial displacement and degree of corrosion is derived, the critical degree of corrosion can be obtained. The mesoscale model demonstrated its validity as it predicted the critical degree of corrosion and cracking patterns in good agreement with analytical solutions and experimental results. The model demonstrates how the random distribution of coarse aggregate results in a variation of critical degrees of corrosion, which follows a normal distribution. A parametric study was conducted, which indicates that both the mean and variation of critical degree of corrosion increased with the increase of concrete cover thickness, coarse aggregates volume fraction and decrease of coarse aggregate size. In addition, as tensile strength of concrete increased, the average critical degree of corrosion increased while its variation almost remained unchanged.

• Corrosion Science and Technology
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• v.15 no.1
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• pp.18-27
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• 2016

In this study, the accelerated corrosion test by combined deteriorating action of salt damage and freeze-thaw was investigated. freeze-thaw cycle is one method for corrosion testing; corrosion initiation time was measured in four types of concrete samples, i.e., two samples mixed with fly ash (FA) and blast furnace slag (BS), and the other two samples having two water/cement ratio (W/C = 0.6, 0.35) without admixture (OPC60 and OPC35). The corrosion of rebar embedded in concrete occurred most quickly at the $30^{th}$ freeze-thaw cycle. Moreover, a corrosion monitoring method with a half-cell potential measurement and relative dynamic elastic modulus derived from resonant frequency measures was conducted simultaneously. The results indicated that the corrosion of rebar occurred when the relative dynamic elastic modulus was less than 60%. Therefore, dynamic elastic modulus can be used to detect corrosion of steel bar. The results of the accelerated corrosion test exhibited significant difference according to corrosion periods combined with each test condition. Consequently, the OPC60 showed the lowest corrosion resistance among the samples.