• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.121-128
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• 2005

This study focuses on evaluating the reliability index of a deck of RC slab having chloride contamination and studying the relation of grades of rebar corrosion and the reliability index of a bridge deck For this purpose, first, the failure probability related to flexural strength was calculated using a model for deterioration, which contains the application of deicing salts that usually causes significant long-term deterioration and reduction in the structural safety for strength of structure. And also, according to the depth of covering, the chloride contents depending on time due to depths of RC slab deck, the appearance time for initial corrosion of rebar and the occurrence time for split of covering were investigated using a MCS method.

• Magazine of the Korea Concrete Institute
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• v.9 no.6
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• pp.233-241
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• 1997

최근 해안환경하에 있는 콘크리트구조물의 철근부식은 구조물의 내구성 저하 및 유지관리라는 차원에서 커다란 문제점을 가지고 있다. 이와 같은 현상은 해양구조물의 건설이 날로 증가하고 있고, 또 콘크리트 제조시 잔골재의 일부를 염분이 함유된 해사를 사용함으로써 더욱 심각해지고 있다. 본 연구에서는 콘크리트 표면으로부터 침투해 들어오는 침입염분의 거동을 모델화하였으며, 콘크리트 세공속의 수용액상에 있은 염화물이온의 확산을 포함하는 물리 화학적 진행, 시멘트 수화물에 고정되는 염분의 흡착과 탈착 및 고정염과의 화학반응 등의 현상을 유한요소법에 의해 해석을 실시하였다. 본 연구의 결과는 콘크리트 내부의 철근 발청시기의 예측, 해안환경하에 있는 콘크리트 구조물의 침투 염분에 의한 콘크리트 덮개의 결정, 콘크리트 구조물의 염화물이온의 허용치 설정을 비롯하여 내구년수를 예측하는데 유용하게 활용될 수 있을 것으로 기대된다.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.679-686
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• 2005

The corrosion of reinforcement induced by chloride ingress is the main deterioration cause of coastal reinforced concrete structures. In this paper, an experimental study was executed to investigate the effect of the kinds and replacement ratios of mineral admixtures (fly-ash, ground granulated blast-furnace slag silica fume and meta-kaolin), W/B and curing time on chloride diffusion of concrete by long-time immersion test in chloride solution. According to the result, the use of mineral admixtures was effective in improving the resistant to chloride ingress. The chloride penetration depth and diffusion coefficient were decreased as replacement ratios of mineral admixture were increased. The kind and replacement ratio of the mineral admixture are more important than the W/B in reducing the chloride diffusion of concrete. Chloride binding capacity of mineral admixture, which was sequenced in the order of MK

• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.931-938
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• 2005

When concrete structures are exposed under marine condition for a long time, the steel in concrete is corroded due to the ingression of chlorides in the seawater. Because the damages of corrosion resulting from the chloride ion are very serious, many researches have been performed. Silver nitrate colormetric method that can measure easily penetration depth of chloride ion has been executed, recent)y. However, characteristics of silver nitrate colormetric method were not fully examined. Therefore, the objective of this paper Is to study the applicability of colormetric method. For the purpose of this, effect factors and reaction mechanism of colormetric method were investigated, and the colormetric method is applied for marine concrete structures. According to the results of silver nitrate colored method, two reactions such as white reaction of AgCl and brown reaction of AgOH were shown when $AgNO_3$ was sprayed in splited section. And velocity constant ratio(K) of two reactions appeared that white reaction, AgCl reacts with the fast speed by 3240. When the colormetric method was applied in concrete, it is reasonable that $AgNO_3$ solution more than 0.05N concentration was sprayed. It is confirmed that the colormetric method is useful tool for estimating the chloride of concrete structures in situ. The average chloride amount of colored parts indicates $0.9kg/m^3$ per concrete unit weight.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.307-314
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• 2017

Concrete is a durable and cost-benefit construction material, however performance degradation occurs due to steel corrosion exposed to chloride attack. Penetration of chloride ion usually decreases due to hydrates formation and reduction of pores, and the reduced chloride behavior is considered through decreasing diffusion coefficient with time. In the work, HPC (High Performance Concrete) samples are prepared with 3 levels of W/B (water to binder) ratios of 0.37, 0.42, and 0.27 and 3 levels of replacement ratios of 0%, 30% and 50%. Several tests containing chloride diffusion coefficient, passed charge, and compressive strength are performed considering age effect of 28 days and 180 days. Chloride diffusion is more reduced in OPC concrete with lower W/B ratio and GGBFS concrete with 50% replacement ratio shows significant reduction of chloride diffusion in higher W/B ratio. At the age of 28 days, GGBFS concrete with 50% replacement ratio shows more rapid reduction of chloride diffusion than strength development, which reveals that abundant GGBFS replacement has effective resistance to chloride penetration even in the early-aged condition.

• Cement Symposium
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• no.28
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• pp.179-186
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• 2001

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.1
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• pp.64-75
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• 2013

As both laboratory accelerated experiment and field exposure experiment were performed, at recent, the fifth field test at five year exposures was proceeded according to long period experimental plan. Field experiment, for the adoption of the developed evaluation model, which is consisted of the analysis of chloride penetration profile at gate bridges of sea-dike completed 30 years ago was carried out during upgrading the basic evaluation model with analyzing the annual field test data. The surface concentration of chlorides was replaced to the concentration of chloride of inner concrete near the surface chlorides among his research results at basic model. Maage's suggestion function was accepted too as a diffusion coefficient of chloride after verifying the change of diffusion coefficient by analysis of annual field test data. The comparison of field data with model predictions and the estimation of remaining life time demonstrates that the proposed updated model and maintenance simulation system can be used to predict the chloride penetration profile in the marine tidal zone and appropriate repair period and cost.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4A
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• pp.365-371
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• 2009

It is time-consuming to estimate chloride diffusivity of concrete by concentration difference test. For the reason chloride diffusivity of concrete is mainly tested by electrically accelerated method, which is accelerating the movement of chloride ion by potential difference. In this study, portland cement concrete and concrete containing with ground granulated blast-furnace slag (40 and 60% of cement by weight) with water-cementitious material ratio 40, 45, 50 and 60% were manufactured. To compare with chloride diffusivity calculated from the electrically accelerated test and immersed test in artifical seawater, chloride diffusivity tests were conducted. From the results of regression analysis, regression equation between accelerated chloride diffusivity and immersed chloride diffusivity was linear function. And the determinant coefficient was 0.96 for linear equation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.5
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• pp.66-74
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• 2016

The objective of this study is the investigation of the influence of carbonation on the penetration of chloride ions in reinforced concrete sections for different mix proportions and environmental conditions. A comprehensive numerical model based on the change of the pore structure and the chemical equilibrium was used for this combined action of carbonation and chloride ingress. The empirical formulae of some parameters in this model are estimated according to numerous experimental data. And, a set of data analysis is carried out to simplify the estimation of model variables to reduce the computational cost. A coupled simulation of the transports of carbon dioxide, chloride ions, heat and moisture is carried out. Then, the parametric analysis is given and the numerical results show that the effect of carbonation of the free chloride ingress is significant and depends on the binder types and concrete mix proportion.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.93-100
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• 2014

Steel reinforcement buried in concrete structure in submerged zone does not easily become corroded due to lack of dissolved oxygen. For that reason, accelerated corrosion test in submerged state is performed with an electrochemical method, which is not suitable for actual corrosion mechanism and makes it difficult to find relevance with long-term behavior. In this study, accelerated corrosion test was performed with the temperature and chloride concentration as main variables in order to establish a method for accelerated corrosion test in submerged zone. Corrosion was determined by the result of reinforcement corrosion monitoring based on galvanic potential measurement and half-cell potential method. The accelerated corrosion test result showed that temperature had the most dominant influence. To determine the chloride content, chloride concentration by depth in the test sample was measured. With the same conditions, chloride penetration interpretation was performed by DuCOM, a FEM durability interpretation program. Also, a test was performed to measure dissolved oxygen according to soaking conditions of artificial seawater, which was used for verifying the validity of the accelerated corrosion test result.