• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.707-715
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• 2007

The vulnerability of concrete to its environment is significantly dependent on the fact that concrete is a porous material. For well-consolidated and well-cured concrete, its service life is a very long and an entrance of aggressive substance might be only pores. However, for cracked concrete, cracks should be preferential channel for the penetration of aggressive substance such as chloride ions. The effect of crack on chloride penetration depends on its size for example, crack width and crack depth. The purpose of this study is examining the effect of crack width and crack depth on chloride penetration. In order to visualize chloride penetration via cracks, RCM (rapid chloride migration) testing is accomplished. Crack width is examined using an optical microscope and CMOD value is used to estimate average crack width. From the examination on the trend of chloride diffusion coefficients of concrete specimens with various crack widths, a critical crack width and a critical crack depth are found out.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.751-760
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• 2005

The chloride penetration model, which considers diffusion and sorption, is proposed. The FEM program developed on the basis of the diffusion and sorption model provides the estimation of chloride concentration variation according to cyclic humidity and temperature. The humidity diffusion analysis is carried out, and the chloride ion diffusion and sorption analysis are conducted on the basis of the pre-estimated humidity data in each element. Each element has different variables at different ages and locations in analysis. At early ages, the difference of relative humidity between inner and outer concretes causes the chloride ion penetration by sorption. As the humidity diffusion reduces the difference of relative humidity between inner md outer concretes with age, the effect of sorption on the chloride ion penetration decreases with age. The cyclic humidity increases the effect of sorption on the chloride ion penetration at early ages, and increases the quantity of chloride ion around steel at later ages. Therefore, the in-situ analysis of chloride ion Penetration for harbor concrete structures must be Performed considering the cyclic humidity conditionandthelongtermsorption.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.404-405
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• 2011

원전구조물의 방사성 폐기물 처분시설의 경우 지하수에 해수가 유입되어 콘크리트에 염소이온 침투가 발생할 수 있으며, 콘크리트 내부에 존재하는 인장철근의 부식에 의한 내구성 저하 및 수명 단축이 주된 문제가 된다. 본 논문에서는 원전콘크리트 구조물에서의 확산에 의한 염소이온 침투에 대한 수학적 모델을 제시하였다. 콘크리트 중의 염소이온의 침투는 콘크리트의 노출환경, 습윤상태에 따라 확산(Diffusion), 대류(Absorption), 전기적 이동(Migration)에 의해 발생한다. 이러한 조건을 모두 고려하여 제시한 방정식에 의해 염소이온의 침투를 예측할 수 있다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.6
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• pp.607-615
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• 2009

Analysis of chloride penetration into concrete is performed considering the repeated wetting and drying conditions of tidal zone, by means of the developed finite element program which enables the diffusion-convection analysis to be conducted. Heat conduction and moisture diffusion are also included in the finite element analysis program in order that their effects to chloride penetration may be considered. For the efficiency of calculation, the analyses of temperature, relative humidity and free chloride concentration are conducted successively in that order, by treating the convection of chloride due to moisture diffusion as an source or sink term. By comparing the analysis result from finite element analysis, where main variable is a wetting and drying period, with the chloride profiles from ACI Life-365 method, it is shown that the Life-365 method gives an accurate result for the submerged zone but does not consider the differences of wetting and drying period. To obtain an accurate chloride profile in the tidal zone, it is confirmed that the diffusion-convection finite element analysis should be applied.

• Journal of the Korea Concrete Institute
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• v.15 no.1
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• pp.25-34
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• 2003

The degradation of reinforced concrete (RC) structures due to physical and chemical attacks has been a major issue in construction engineering. Deterioration of RC structures by chloride attack followed by reinforcement corrosion is one of the serious problems. An objective of this study is to develop a form of mathematical model of chloride ingress into concrete. In order to overcome some limits of the previous approaches, a chloride ingress model, consisting of chloride solution intrusion through the capillary pore and chloride ion diffusion through the pore water, was proposed. Moreover, the variability of chloride ion diffusivity due to the degree of hydration of cement, relative humidity in pore, exposure condition, and variation of chloride binding, was considered in the model. In order to verify the proposed model, the results predicted by the proposed model were compared with analysis results of Life-365, a computer program for predicting the service life of reinforced concrete structures exposed to chlorides. In conclusion, the proposed model would be promising to predict the chloride ion profile and to estimate the service life of RC structures.

• Journal of the Korea Computer Industry Society
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• v.9 no.3
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• pp.137-142
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• 2008

The major influence factor on chloride penetration into concrete structures is chloride ion concentration. In this study, chloride penetration analyses with chloride ion concentration were carried out by the developed program. Also, the service life of concrete structures was predicted. The penetration depth was 32mm in case that chloride ion concentration wad 600ppm. It was shown that the service life of concrete structures with 40mm cover depth was 167 years even though they had been exposed at chloride ion concentration 600ppm during 100 years.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.467-468
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• 2010

Over the past few decades, considerable numbers of studies on the durability of concrete have been carried out extensively. The majority of these researches have been performed on sound uncracked concrete, although most of in-situ concrete structures have more or less micro-cracks. It is only recent approach that the attention has shifted towards the influence of cracks and crack width on the penetration of chloride into concrete. The penetration of chlorides into concrete through the cracks can make a significant harmful effect on reinforcement corrosion. Author of this study examined the effect of cracks on chloride penetration by short term experiment. However, it is necessary to accomplish the effect by long term experiment to get reliable goal. In this study, the long term and short term experiments were carried out. This can be useful for establishing new species model of chloride penetration through cracks in concrete.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.57-65
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• 2007

Over the past few decades, considerable numbers of studies on the durability of concrete have been carried out extensively. A lot of improvements have been achieved especially in both measuring techniques as well as modeling of ionic flows. However, the majority of these researches have been performed on sound uncracked concrete, although most of in-situ concrete structures have more or less micro-cracks. It is only recent approach that the attention has shifted towards the influence of cracks and crack width on the penetration of chloride into concrete. The penetration of chlorides into concrete through the cracks can make a significant harmful effect on reinforcement corrosion. On the other hand, a general acceptable crack width of 0.3 mm has been recognized for keeping the serviceability of concrete structures in accordance with a lot of codes. However, there seems to be rare established description to explain the critical crack width in terms of the durability of concrete. To make a bad situation worse, there is little agreement on critical crack width among a few of literatures for this issue. Critical crack width is still controversial problem. Nevertheless, since the critical crack width is important key for healthy assessment of concrete structures exposed to marine environment, it should be established. The objective of this study is to define a critical crack width. The critical crack width in this study is designed for a threshold crack width, which contributes to the first variation of chloride diffusion coefficient in responsive to the existence of cracks. A simple solution is formulated to realize the quantifiable parameter, chloride diffusion coefficient for only cracked zone excluding sound concrete. From the examination on the trend of chloride diffusion coefficient of only cracked zone for various crack widths, a critical crack width is founded out.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.729-735
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• 2008

For well-constructed concrete, its service life is a long period and it has an enough durability performance. For cracked concrete, however, it is clear that cracks should be a preferential channel for the penetration of aggressive substance such as chloride ions accoding to author's previous researches. Even though crack width can be reduced due to the high reinforcement ratio, the question is to which extend these cracks may jeopardize the durability of cracked concrete. If the size of crack is small, surface treatment system can be considered as one of the best options to extend the service life of concrete structures exposed to marine environment simply in terms of cost effectiveness versus durability performance. Thus, it should be decided to undertake an experimental study to deal with the effect of different types of surface treatment system, which are expected to seal the concrete and the cracks to chloride-induced corrosion in particular. In this study, it is examined the effect of surfaced treated systems such as penetrant, coating, and their combination on chloride penetration through microcracks. Experimental results showed that penetrant can't cure cracks. However, coating and combined treatment can prohibit chloride penetration through cracks upto 0.06 mm, 0.08 mm, respectively.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.11-17
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• 2011

A major source of durability problems in concrete structures is the corrosion of steel by the damage of passivity layer around steel bars. As chloride ion penetration is major cause of the destruction of passivity layer, evaluation of depth and concentration profile of chloride ion is the essential factor for the service-life estimation of concrete structure. To estimate chloride ion penetration characteristics, this paper on the basis of in-situ experimental data investigated the depth and concentration profile of chloride ion penetration. The core specimens are obtained at air-zone, splash zone, and tidal zone in Wando, Masan, Incheon, Gwangyang, and donghae harbors. Colorimentric method measured the chloride ion penetration depth and ASTM C 114 evaluated the concentration profile of chloride ion. Based on experimental data, the influence of harbor location and exposure condition on chloride ion penetration is evaluated.