• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.117-125
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• 2017

The role of fly ash in concrete become impotent with finding the characteristics of fly ash in which it is used as cement replacement material. In this paper, corrosion test results obtained by two test methods such as the long-term exposure corrosion test and the accelerated corrosion test method, were compared to investigated the corrosion resistance between fly ash concrete and normal concrete. Corrosion initiation time was measured in two types of concrete, i.e., one mixed with fly ash(FA) and the other without admixture(OPC). The accelerated corrosion test was carried out by four case, i.e., two samples is a cyclic drying-wetting method combined without carbonation(case 1) and combined with carbonation(case 2), and the other two samples is a artificial seawater ponding test method combined without carbonation(case 3) and combined with carbonation(case 4). Whether corrosion occurs, it was measures using half-cell potential method. The ponding test combined without carbonation was most effective in accelerating corrosion time of steel bars. The results indicated that the corrosion of rebar embedded in concrete occurred according to the order of OPC, FA. The delay relative ratio of corrosion obtained by corrosion initiation time between FA and OPC is 1.04 to 1.27. Consequently, fly ash concrete as the age increases its corrosion resistance was improved compared with OPC concrete.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2003.08a
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• pp.158-163
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• 2003

한반도 서ㆍ남해안은 크고 작은 만과 해빈, 삼각주, 하구, 조간대 등 다양한 연안해역이 잘 발달 되어 있다 평균조차는 서해안 남부에서 약 3m로 북쪽으로 갈수록 증가하여 군산 부근에 6m, 인천 부근에서 약 8m에 달하며, 남해안의 평균조차는 부산 1.2m, 진해 2.1m, 충무 2.6m, 삼천포 3.0m, 여수 3.3m, 완도 3.5m, 목포 3.7m로 조석 간만의 차가 크게 나타나서 연안해역에 폭넓은 조간대가 형성되어 있다. (중략)

• Journal of the Korea Institute of Building Construction
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• v.14 no.5
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• pp.397-405
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• 2014

There are many literatures reporting that the service life of re-bars in concrete structures is reduced in the oceanic environment due to chloride attack. To solve this problem, this study used geo-polymer as a mix material for concrete to increase its resistance to salt damage, and the external voltage method, one of the electric methods, is was applied to evaluate the likelihood of re-bars in the oceanic structure being exposed to the extreme salt environment. The items evaluated include the natural potential of re-bars and the corrosion rate. The results of the tests showed that in all of the salt environmental conditions (submerged zone, tidal zone, and crack), the tested materials were remarkably effective compared with ordinary concrete. The corrosion protective property was found not only in the evaluation of the natural potential but also in the evaluation of the corrosion rate, suggesting that the external voltage method can be used stably for geo-polymer RC structures in an extreme salt environment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.5
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• pp.67-74
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• 2015

RC (Reinforced Concrete) structures are considered as cost-benefit and durable however performances of structural safety and durability are degraded due to steel corrosion. Service life in RC structure is differently evaluated due to different local environmental conditions even if it is exposed to the same chloride attack. In the paper, 25 concrete cores from field investigation are obtained from 4 RC columns with duration of 3.5~4.5 years exposed to sea water. Through total chloride content measurement, surface chloride contents and apparent diffusion coefficients are evaluated. Service life of the target structure is estimated through deterministic method based on Fick's $2^{nd}$ Law and probabilistic method based on durability failure probability, respectively. Probability method is evaluated to be more conservative and relatively decreased service life is evaluated in tidal zone and splash zone over 40.0 m. Chloride penetration behavior with coring location from sea level and the present limitations of durability design method are investigated in the paper.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.4
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• pp.307-313
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• 2014

Recent interest in the increased structural performance and durability evaluation of this concrete structure in a salt damage environment is increasing. The most secure and reliable method of accelerated corrosion test is a method to carry out the rebar corrosion monitoring can be exposed directly to the marine test site exposure. However, long-term exposure testinghas the disadvantage that a long period is necessary. So, a lot of research on RC of salt damage environment have beenpromoted as alternatives to replace this. However, accelerated corrosion test, in the short term only is appropriate and is but an accelerated test method to evaluate the critical chlorine concentration, there is a difficult problem that you still get the answer. It is one of the correlation problems accelerated test correspond to a certain period of exposure environment. Therefore, in this study, to clarify the differences rebar corrosion beginning, through the actual corrosion accelerated test in corrosion time and laboratory test chamber of the structure of the marine environment results in both environments, it is an object of correlation coefficient derived.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.773-776
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• 2008

The corrosion of steel in concrete is significant in marine environment. Marine bridges are readily deteriorated due to the exposure to marine environment. Salt damage is one of the most detrimental causes to concrete bridges and port structures. Especially, the splash and tidal zones around water line are comparatively important in terms of safety and life-time point of view. During the last several decades, cathodic protection (cp) has been commonly accepted as an effective technique for corrosion control in concrete structures. Zn-mesh sacrificial anode has been recently developed and started to apply to the bridge column cp in marine condition. The detailed parameters regarding Zn-mesh cp technique, however, have not well understood. This study is to investigate how much Zn-mesh cp influences along the concrete column at elevated temperature. About 100cm column specimens with eight of 10cm segment rebars have been used to measure the variation of cp potential with the distance from Zn-mesh anode at both 10$^{\circ}$C and 40$^{\circ}$C in natural seawater. The cp potential change and current diminishment along the column specimens have been discussed for the optimum design of cp by Zn-mesh sacrificial anode

• 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.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.730-737
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• 2014

In this study, chloride content of marine concrete bridge at the south coast in 5~34years was calculated based on the measured data and the validity of the proposed value was evaluated. Also, correlation of existence of salt injury prevention coating, chloride content, carbonation depth and the compressive strength of marine concrete bridges were derived and relationship of the four was evaluated. According to the research results, surface chloride content value in the tidal zone proposed form KCI 2009 and value in the splash zone and atmospheric zone proposed form Cheong et al.(2005) was the most valid. Also, salt injury prevention coating of marine concrete bridges had the outstanding effect of preventing chloride content penetration, carbonation depth and reduction in the compressive strength. Compressive strength of concrete was reduced by the increase of carbonation depth and chloride content.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4542-4551
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• 2013

Recently, much attention has focused on the study of eco-friendly concrete using recycled by-products for protecting marine ecosystem and durability of concrete exposed to marine condition. This study evaluated the durabilities of 4 different type of concrete mixtures(Control, Marine, Porous, New slag) with the seawater resistance by marine environment exposure experiment and freeze-thaw resistance, resistance to chloride ion penetration considering severe deterioration environment. In this study, we conducted seawater resistance using compressive strength according to the age(7/28/56 days) of specimen and curing conditions(standard(fresh water), tidal, immersion, artificial seawater). The results show that compressive strength of concrete exposed to marine environment exposure condition was lower than those of the standard curing condition. Also, compressive strength of New slag using eco-friendly materials for protecting marine ecosystem was lower than those of other concretes, there is need to improve the performance of New slag. The results for freeze-thaw resistance showed that all mixtures have excellent, but the Porous and New slag were lower than others. Also, the more improved resistance to chloride ion penetration than those of the Marine was measured in the New slag regardless of curing condition.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.149-156
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• 2016

The service life in RC (Reinforced Concrete) is very important and it is usually obtained through deterministic method based on Fick's 2nd law and probabilistic method. This paper presents an evaluation of $P_{df}$(durability failure probability) and the related service life considering time-dependent behaviors in chloride diffusion and surface chloride content. For the work, field investigation is performed for RC structures exposed to chloride attack for 3.5~4.5years, focusing tidal zone (6.0 m) and sea shore (9.0 m), respectively. Random variables like cover depth, chloride diffusion coefficient, and surface chloride content are obtained, and $P_{df}$ and the service life are evaluated. Unlike the results from deterministic method using LIFE 365, probabilistic method with time effects on diffusion and surface chloride shows a relatively rapid change in the result, which is a significant reductions of service life in the case with low surface chloride content. For probabilistic evaluation of durability, high surface chloride content over $10.0kg/m^3$ is required and reasonable service life can be derived with consideration of time-dependent diffusion coefficient.