• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.46-52
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• 2017

Recently durability design based on deterministic or probabilistic method has been attempted since service life evaluation in RC(Reinforced Concrete) structure exposed to chloride attack is important. The deterministic durability design contains a reasonable method with time effect on surface chloride content and diffusion coefficient, however the probabilistic design procedure has no consideration of time effect on both. In the paper, a technique on PDF(Probability of Durability Failure) evaluation is proposed considering time effect on diffusion and surface chloride content through equivalent surface chloride content which has same induced chloride content within a given period and cover depth. With varying period to built-up from 10 to 30 years and maximum surface chloride content from $5.0kg/m^3$ to $10.0kg/m^3$, the changing PDF and the related service life are derived. The proposed method can be reasonably applied to actual durability design with preventing conservative design parameters and considering the same analysis conditions of the deterministic method.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.794-801
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• 2003

As it is important to measure the degree of the deterioration and predict service life caused by chloride in concrete structure the methods of measuring chloride in the concrete is raised important problems. This study is to set a new standard for using of the colorimetric method through grasping the character of the colorimetric distinction method, and measuring the chloride content at the place discolored. Also, to predict chloride content around embeded bar and time reaching limit chloride concentration through measuring the chloride content of concrete surface by colorimetric distinction method and this study presents the new concept of concrete degradation and diagnosis of the durability by salt damage. According the results, it is possible to use colorimetric distinction method as simplified measurement to measure the fixed quantity of the chloride concentration. What is more, it would make calculation of concrete surface chloride had a wide fluctuation at the general environment extended. Also, it would be make estimating durability of reinforced concrete structures applied to the basic data.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.236-245
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• 2021

It is very important for structure designer to understand the service life variation since a wide range of service life is evaluated with changing exposure conditions and design parameters. Recently, for zero-carbon, waste plastic has been used for fuel for clinker production and this yields increase in chloride content in cement. This study is for evaluation of changing service life in the concrete with increasing initial chloride content due to usage of plastic-SRF(Solid Refuse Fuel) considering various exposure conditions and design parameters. For this, 4 levels of initial chloride content were assumed, and the service life was assessed using LIFE 365 program considering various environmental conditions including 3 levels of surface chloride content. As for analysis parameters, critical/initial chloride content, blast furnace slag powder replacement ratio, W/B(Water to Binder) ratio, cover depth, and unit mass for binder are adopted. Service life decreases with increasing initial chloride content and a significant reduction of service life is not evaluated permitting up to 1,000ppm of initial chloride content. With increasing slag replacement ratio, a longer service life can be secured since blast furnace slag powder has the effect of reducing the diffusion of external chloride ions and fixing the free chloride. It is thought that increasing initial chloride content up to European standard is helpful for enhancing sustainability and reducing carbon emission. Though the reduction in service life due to an increase in the initial chloride content is not significant in slag-concrete with low surface chloride content, careful consideration for mixing design should be paid for the exposure environment with high surface chloride content.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.36-42
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• 2018

GGBFS(Ground Granulated Blast Furnace Slag)-replacement is very effective for improving resistance to chloride attack and this can induce a long service life for RC(Reinforced Concrete) structures exposed to chlorides. In the work, the design parameters such as cover depth, surface chloride content, critical chloride content, and replacement ratio of GGBFS are considered, and optimum replacement ratio of GGBFS are derived with intended service life. The changes of surface chloride content and cover depth show 3.16~3.38 and 3.02~3.34 times of service life variation, which are most influencing parameters. Critical chloride content shows 1.53~1.57 times of service life variation regardless of w/b(Water to Binder) ratios. In the case of surface chloride content $18.0kg/m^3$, the most severe condition, cover depth over 70 mm and GGBFS replacement ratio over 42% are required with concrete containing w/b ratio under 0.42 for 100 years of intended service life. The condition of $13.0kg/m^3$, GGBFS replacement over 35% is required. For reasonable durability design, quantitative exterior condition and critical chloride content should be determined, and the criteria in Domestic Specification is evaluated to be conservative.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.6
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• pp.18-25
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• 2019

The cracks occurred during service life of concrete structure should be considered in durability design, because of the concrete's material property which is weak in tensile strength. In this study, the fly ash concrete mixtures considering 2 levels of strength is designed and outdoor exposure tests are conducted for those concrete specimens. The exposure environment is set to a splash zone, and in order to evaluate the effect of crack width on the behavior of chloride diffusion, the crack width of up to 1.0 mm is generated at intervals of 0.1 mm at each concrete mixture. After that, apparent chloride diffusion coefficient and surface chloride contents are deducted considering 3 levels of exposure periods(180 days, 365 days, 730 days). The diffusion coefficients of two types of mixture increase with the increase of crack width, and the diffusion coefficients decrease with the increase of exposure periods. In addition, the effect of the crack width on the diffusion coefficient is reduced as the exposure periods increase, which is attributed to the extra hydrate by chloride ion reducing the diffusivity of concrete. The behavior of the surface chloride contents does not significantly change by the increase in crack width, compared to the behavior of apparent chloride diffusion coefficient. Also, In the high strength FA concrete mixture, the surface chloride contents are 78.9 % ~ 90.7 % than the normal FA strength concrete mixture. Thus, Surface chloride contents have correlation with the strength of concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.16-22
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• 2023

In this study, a salt water immersion test was performed on concrete specimens simulating the concrete mix design of the nuclear power plant, and the correlation between the amount of chloride and the XRF component according to the depth of the concrete was analyzed. The amount of chloride on the surface of the nuclear power plant concrete increased slightly with increasing immersion time in salt water, but the amount of chloride in the depth of 5.5 mm or more showed a clear tendency to increase with increasing immersion time in salt water. As a result of analyzing the correlation between the amount of chloride in concrete and the XRF component, the concrete with 20% FA substitution compared with the OPC concrete showed a very high correlation between the composition ratio of Cl ions and the evaluation result of salt damage resistance by XRF component analysis. Accordingly, it was confirmed that chlorine ion analysis and salt damage resistance performance evaluation by XRF component analysis were possible through repeated data accumulation in the nuclear power plant concrete mix with 20% fly ash replacement.

• 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.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.172-179
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• 2016

For an evaluation of service life in RC(Reinforced Concrete) structures, deterministic method and probabilistic method considering random variables of design parameters are usually adopted. In the work, surface chloride contents which vary with distance from sea shore and height are investigated from the previous research literature surveys, and they are considered for service life estimation. Through the analysis, the probabilistic method shows much lower results, which is due to variations of design parameters and very low intended durability failure. In the deterministic method, the structures within 250m and higher than 60m are evaluated to be free from chloride attack. In the probabilistic method, those higher than 60m in all the region and higher than 40m and 250m from sea shore are evaluated to satisfy the service life.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.585-588
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• 2008

To predict the service life of reinforced concrete structures exposed to chloride environment, quantitative measures of material properties such as the critical chloride content for corrosion in concrete and the diffusion coefficient of chloride ions of concrete and the surface chloride content of the concrete are essential. However, it should be noted that they are influenced by several factors such as concrete mix proportions, cement type, and environmental conditions, etc. Thus, the purpose of this research is to estimate more actually the critical chloride content for corrosion of the reinforcing steel in concrete by field exposure experiment. For this purpose, the prism concrete test specimens were made for water-cement(W/C) ratios of 31%, 42%, 50%, and 70%, and then the field exposure experiment for them were conducted at Youngduk of the east coast for about 3 years. During the test, corrosion monitoring by half cell potential method was carried out to detect the time to initiation of corrosion for test specimens and its chloride content was evaluated by breaking the concrete test specimens when corrosion of the reinforcing steel in concrete was perceived. It was observed from the test results that the critical chloride content for corrosion of reinforcing steel in concrete would be dependent on W/C ratio and almost irrespective of concrete cover.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.65-72
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• 2016

Service life evaluation for RC Structures exposed to chloride attack is very important, however the previous two methods(deterministic and probabilistic method) show a big difference. The paper presents a service life simulation using deterministic and probabilistic method with time-dependent diffusion coefficient. Three different cases are considered for diffusion coefficient, concrete cover depth, and surface chloride content respectively, and then the PDF(probability of durability failure) and the related service life are obtained. Through adopting time-dependent diffusion, the discrepancy between the two methods can be reduced, which yields reasonable service life. When diffusion coefficient increases from $2.5{\times}10^{-12}m^2/sec$ to $7.5{\times}10^{-12}m^2/sec$, the service life decreases to 25.5~35.6% level, and cover depth does from 75 mm to 125 mm, it increases to 267~311% level as well. In the case of surface chloride content from $5.0kg/m^3$ to $15.0kg/m^3$, it changes to 40.9~54.5%. The effect of cover depth is higher than the others by 8~10 times and also implies it is a key parameter to service life extension.