• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 가을 학술발표회 논문집
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• pp.87-92
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• 1994

The main objective of this study is to determine the critical chloride ion concentrations in the pore solutions causing depassivation of steel reinforcement in concrete made with cements of different $C_3A$ contents. Cement pastes with water-ratio of 0.5 were prepared using four cements with $C_3A$ contents of 0.46, 5.97, 9.14, and 9.65 percent. The pastes were allowed to hydrate in sealed containers for 28days and then objected to pore solution expression. The expressed pore fluids were analyzed for chloride and hydroxyl ion concentrations. It was found that the free cholride concentration in the pore solution decreases significantly with an increase in the $C_3A$ content of the cement. With increasing level of chloride addition, although the alsolute amount of bound chloride increase, the ratio of bound to total chlorides decreases.

• 한국해양공학회지
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• 제12권3호통권29호
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• pp.68-74
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• 1998

An increase of concrete construction in marine environments as well as an increasing use of marine aggregate at the mixing stage of concrete has provoked an important problem. A high concentration of chloride ion in the vicinity of steel bars in concrete is the principal cause of premature reinforcement corrosion in concrete structures. In this study, the behavior of chloride ions introduced into concrete from concrete surface by marine evironment was analysed. A mathematical model including the diffusion of chloride ion in aqueous phase of pores, the adsorption and desorption of chloride ions to and from the surface of solid phase of concrete and the chemical reactions of chloride ions with solid phase was presented. Finite element method was employed to carry out numerical analysis. The results of this study may be used to predict the onset of reinforcement corrosion and to identify the maximum limit of chloride ions contained in concrete admixtures.

• Computers and Concrete
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• 제10권3호
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• pp.219-229
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• 2012

Carbonation is a widespread degradation of concrete and may be coupled with more severe degradations. An experimental investigation was carried out to study the effect of carbonation on chloride ion diffusion of concrete. The characteristic of concrete after carbonation was measured, such as carbonation depth, strength and pore structure. Results indicated that carbonation depth has a good linear relation with square root of carbonate time, and carbonation can improve compressive strength, but lower flexural strength. Results about pore structure of concrete before and after carbonation have shown that carbonation could cause a redistribution of the pore sizes and increase the proportion of small pores. It also can decrease porosities, most probable pore size and average pore diameters. Chloride ion diffusion of concrete after carbonation was studied through natural diffusion method and steady state migration testing method respectively. It is supposed that the chloride ion concentration of carbonation region is higher than that of the sound region because of the separation of fixed salts, and chloride ion diffusion coefficient was increased due to carbonation action evidently.

• Computers and Concrete
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• 제7권5호
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• pp.421-435
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• 2010

This paper utilizes the modified Davis model and the mode coupling theory, as parts of the electrolyte solution theory, to investigate the diffusivity of the ion in concrete. Firstly, a computational model of the ion diffusion coefficient, which is associated with ion species, pore solution concentration, concrete mix parameters including water-cement ratio and cement volume fraction, and microstructure parameters such as the porosity and tortuosity, is proposed in the saturated concrete. Secondly, the experiments, on which the chloride diffusion coefficient is measured by the rapid chloride penetration test, have been carried out to investigate the validity of the proposed model. The results indicate that the chloride diffusion coefficient obtained by the proposed model is in agreement with the experimental result. Finally, numerical simulation has been completed to investigate the effects of the porosity, tortuosity, water-cement ratio, cement volume fraction and ion concentration in the pore solution on the ion diffusion coefficients. The results show that the ion diffusion coefficient in concrete increases with the porosity, water-cement ratio and cement volume fraction, while we see a decrease with the increasing of tortuosity. Meanwhile, the ion concentration produces more obvious effects on the diffusivity itself, but has almost no effects on the other ions.

• 한국건설순환자원학회논문집
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• 제11권4호
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• pp.381-390
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• 2023

본 연구에서는 염해를 받은 콘크리트의 역학적 성능 평가를 수행하고, 실험 결과를 바탕으로 염소이온 농도에 따른 압축응력변형률 모델을 제시하였다. 염해를 모사하기 위해 콘크리트 배합 시 CaCl₂ 용액을 첨가하였으며, 염소이온의 농도는 결합재의 중량 대비 0, 1, 2, 4 %가 되도록 하였다. 콘크리트의 최대 압축응력 이후의 응력-변형률 곡선을 조사하기 위해 변위 제어를 통해 압축강도를 측정하였다. 염소이온 농도가 1 %인 경우에는 최대 압축응력이 증가하였으나, 염소이온 농도가 2 % 이상인 경우에는 최대 압축응력이 감소하였다. 최대 압축응력에서의 변형률의 경우 재령 7일의 시편에서는 염소이온 농도에 따른 경향이 나타나지 않았다. 재령 28일의 시편에서는 염소이온 농도가 증가함에 따라 감소하였다. 재령 28일의 최대 압축응력와 변형률의 변화를 이용하여 Popovics model에 기반한 응력-변형률 곡선 모델을 제시하였다. 염소이온의 농도 증가에 따른 역학적 성능 저하의 원인을 조사하기 위해 수화생성물 분석을 수행하였다. 염소이온의 농도가 증가함에 따라 Friedel's salt가 증가하고, portlandite가 감소하는 것을 확인하였다.

• 대한공간정보학회지
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• 제19권4호
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• pp.23-33
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• 2011

본 연구에서는 GIS 공간보간법을 이용하여 전라북도 서해안지역의 지하수관정 염소이온 농도를 분석하였다. 특히 해수침투를 평가하기 위해 지하수관정중 검정점을 지정하였으며, 역거리가중치, 스플라인 그리고 크리깅 보간법에 의한 염소이온 농도의 오차특성 분석이 수행되었다. 본 연구의 주요 결론으로서 첫째, 485개 지하수 관정의 염소이온 농도 자료를 이용하여 공간 보간법의 오차특성을 분석한 결과 IDW 방법이 해수침투에 의한 염소이온 농도를 추정하는데 가장 적합한 것으로 나타났다. 둘째, 대상지역의 평균 염소이온 농도를 분석한 결과, 군산시가 $541mg/{\ell}$로서 공업용수 수질기준에도 미달하는 것으로 나타났다. 그리고 김제시와 고창군은 먹는물 수질기준을 만족하는 것으로 나타났으며 부안군은 $272mg/{\ell}$로서 먹는물 수질기준에 약간 미달하는 것으로 분석되었다. 셋째, 행정구역별 분석에서 군산시는 서해안에 접해 있는 대명동, 중동, 장재동, 금암동의 평균 염소이온 농도가 매우 높게 분석 되었으며, 만경강과 접해 있는 회현면과 대야면도 공업용수 수질기준에도 미달하는 등 전반적으로 해수침투에 의한 영향이 큰 것으로 나타났다.

• 한국안전학회지
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• 제22권3호
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• pp.57-64
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• 2007

Recently, the corrosion of concrete structures has received great attention related with the deterioration of sea-side structures, such as new airport, bridges, and nuclear power plants. In this regards, many studies have been done on the chloride attack in concrete structures. However, those studies were confined mostly to the single deterioration due to chloride only, although actual environment is rather of combined type. The purpose of the present study is, therefore, to explore the influences of carbonation and freezing-thawing action to chloride attack in concrete structures. The test results indicate that the chloride penetration is more pronounced than the case of single chloride attack when the carbonation process is combined with the chloride attack. It is supposed that the chloride ion concentration of carbonation region is higher than the sound region because of the separation of fixed salts. Though the use of fly ash pronounces the chloride ion concentration in surface, amounts of chloride ion penetration into deep region decreases with the use of fly ash. The small reduction of relative dynamic elastic modulus induced from freezing-thawing increases the chloride ion penetration depths much. The present study allows more realistic assessment of durability for such concrete structures which are subjected to combined attacks of both chlorides and carbonation or freezing-thawing but the future studies for combined environment will assure the precise assessment.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.515-518
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• 2005

In recent years, many research works have been carried out in order to obtain a more controlled durability and long-term performance of concrete structures exposed to chloride environments. In particular, the development of new procedures for probability-based durability analysis and design has been proved to be very valuable. To carry out the procedures described above, the statistical properties of design valuables such as diffusion coefficient of chloride ion, surface chloride concentration, and chloride threshold value etc. should be known. For this purpose, this paper presents the statistical properties of the diffusion coefficient of chloride ion such as mean value and standard deviation with water-cement(w/c) ratio and curing conditions, respectively. It was observed from the test that the standard deviation for the diffusion coefficient of chloride ion was found to be small with decrease in the w/c ratio irrespective of curing conditions and that of standard curing was found to be smaller than that of field curing.

• 한국구조물진단유지관리공학회 논문집
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• 제10권1호
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• pp.223-230
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• 2006

본 논문에서는 염해에 의하여 열화된 철근콘크리트 구조물의 보수 LCC평가 방법에 대하여 연구를 수행하였다. 또한, 철근콘크리트 구조물의 목표내용년수 동안에 건설초기 공법과 염해보수 공법을 포함한 보수 LCC를 평가하기 위하여 콘크리트내로의 염소이온 침투를 FEM 해석으로 실시함으로써 보수횟수를 결정하였다. 그 결과, 염해 보수 횟수는 보수재의 종류 및 보수방법을 고려한 FEM해석을 통하여 철근위치에서의 염소이온 농도와 철근부식 임계염소이온 농도를 비교함으로써 산정할 수 있었으며, 염해 보수 횟수를 이용하여 목표내용년수 동안의 보수 LCC를 산정하는 것이 가능하였다.

• 대한토목학회논문집
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• 제26권4A호
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• pp.753-759
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• 2006

염해환경 하에 있는 콘크리트 구조물의 내구수명을 예측하기 위하여 콘크리트의 표면 염소이온 농도, 염소이온 확산계수 및 임계 염화물량 등이 주요 인자로 사용된다. 이들 중 염소이온 확산계수는 콘크리트 품질 및 주변 환경조건 등에 많은 영향을 받으며, 이에 따라 콘크리트 구조물의 내구수명이 크게 달라지기 때문에 내구수명을 예측하는 데 가장 중요한 인자로 평가되고 있다. 콘크리트 내의 염소이온 침투 확산에 영향을 미치는 정성적인 주요 인자로는 물-시멘트비, 재령, 양생조건, 주위 환경의 염소이온 농도 및 건습조건 등을 들 수 있는데, 본 연구에서는 염소이온 확산실험을 통해 물-시멘트비와 양생조건이 콘크리트의 염소이온 확산특성에 미치는 영향을 조사하였다. 전위차를 이용한 촉진시험법에 의하여 확산셀을 통과한 전위차를 측정한 후, Andrade의 모델에 의하여 전압강하량을 고려하여 3종류의 물-시멘트비를 갖는 콘크리트의 염소이온 확산계수를 구하였다. 또한, 양생조건별로 물-시멘트비 및 재령 효과를 고려한 회귀분석을 통하여 염소이온 확산계수 추정식을 제안하였다.