• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.78-84
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• 2019

The Marine concrete that located at immersion zone receives an hydrostatic pressure of 1 atm as depth of the water increased by 10 m. And it could accelerate chloride ion penetration. In this study, to evaluate the influence of hydrostatic pressure on chloride ion penetration, concrete mixed by ordinary Portland cement and Portland blast-furnace slag cement was exposed to 1 and 6 atm and substitute ocean water. As a result, the surface chloride ion concentration of the concrete under 6 atm of hydrostatic pressure increased rapidly and the water-soluble chloride ion contents was increased by depth. In addition, the concrete under 6 atm of hydrostatic pressure showed the increase of capillary pores corresponding to 5~100 nm.

• Journal of the Korea Concrete Institute
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• v.26 no.1
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• pp.71-78
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• 2014

The long term integrity of concrete cask is very important for spent nuclear fuel dry storage system. However, there are serious concerns about early deterioration of concrete cask from creaking and corrosion of reinforcing steel by chloride ion because the cask is usually located in seaside, expecially by combined deterioration such as chloride ion and heat, carbonation. This study is to investigate the relation between temperature and chloride ion diffusion of concrete. Immersion tests using 3.5% NaCl solution that were controlled in four level of temperature, i.e. 20, 40, 65, and $90^{\circ}C$, were conducted for four months. The chloride ion diffusion coefficient of concrete was predicted based on the results of profiles of Cl- ion concentration with the depth direction of concrete specimens using the method of potentiometric titration by $AgNO_3$. Test results indicate that the diffusion coefficient of chloride ion increases remarkably with increasing temperature, and there was a linear relation between the natural logarithm values of the diffusion coefficients and the reciprocal of the temperature from the Arrhenius plots. Activation energy of concrete in this study was about 46.6 (W/C = 40%), 41.7 (W/C = 50%), 30.7 (W/C = 60%) kJ/mol under a temperature of up to $90^{\circ}C$, and concrete with lower water-cement ratio has a tendency towards having higher temperature dependency.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.789-795
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• 2002

To evaluate the bind rate and behavior of two types chloride ion-one is the chloride ion added in mixture when un-washed sea sand is used as fine aggregate, one is the chloride ion admitted in the new version of concrete standard specification, pore solution extracted in cement paste were analyzed. The results are follow. 1 As passing the time, the chloride concentration in the pore solution decreases with the Increase in the chloride content absorbed by the hydrate products. As compared with chloride contents in mixing water, the bound ratio of chloride at 49 days is 64∼90％. 2. The bound ratio of chloride in cement paste considering evaporable water as pore solution is obtained. In case of Pl∼P3(added chloride content wt of cement 0.046∼0.16 ％), the bound ratio of chloride is 91.8∼93.5 ％. P4(added chloride wt of cement 0.3％) is 89.1％, but P5(added chloride wt of cement 0.617％) bound is only 77％. 3. The bound ratio of chloride to wt of cement is 0.015∼0.475％ with adding chloride. In case chloride added over 0.091 ％ wt of cement, the bound chloride content increases 1.7∼1.8 times in spite of added chloride increase twice. The bound ratio of chloride to wt of cement decreased with the increase in the chloride content. 4. The more increase added chloride content, the more increase the bound ration of chloride. But the absolute value of chloride content in pore solution increased.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.299-306
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• 2017

In this research, it was examined chloride ion penetration resistance of slag-replaced concrete and cementless slag concrete considering marine environmental exposure conditions of splash zone, tidal zone and immersion zone. In the design strength of grade 24 MPa, the specimens were tested to determine their compressive strength, scanning electron microscopy images and chloride migration coefficient. Further, chloride ion penetration depth and carbonation depth of specimens exposed to marine environment were measured. Experimental results confirm that chloride migration coefficient of specimens tended to decrease with increasing the replacement ratio of ground granulated blast-furnace slag in accelerated laboratory test. In addition, the specimens exposed to the tidal zone were found to be the greatest chloride ion penetration depth compared to splash zone and immersion zone. On the other hand, the chloride ion penetration depth of the specimens exposed to splash zone tended to increase with increasing the replacement ratio of ground granulated blast-furnace slag in contrast with the results for the tidal zone and immersion zone.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.553-557
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• 2022

The present study evaluate the chloride extracion under electrochemical chloride extraction method. Chloride was penetrated into the concrete from external reservoir using a 4M NaCl solution, and an electrochemical chloride extraction method was applied after the curing period of 1 year. The current density was constantly kept 1000 mA/m² for coulostatic application with the variation in potential difference. The duration of the ECE treatment was 2, 4, 8 weeks, respectively. The residual chloride concentration at all depths decreased, and the chloride concentration decreased as the application period increased. After the application period of 8 weeks, 62.9 to 77.6 % of chloride extracted in the total chloride profile, and 77.7 to 99.5 % of chloride extracted in the free chloride profile. In particular, the concentration of free chloride at a depth of 7 mm or more from the concrete surface was 0.01 % or less by cement. In addition, it was confirmed that the bound chloride could be extracted by the electrochemical chloride extraction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.84-91
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• 2014

In this study, in order to find the improvement effect of metakaolin for using improvement of strength in concrete structures, it is investigated the diffusion coefficient of chloride ions and adiabatic temperature rise test. As a result, due to the mixing of metakaolin, it has been confirmed reducing diffusion coefficient of chloride ions and could prevent down of slump for use of adding fly ash. Therefore, ensuring resistance to chloride ion penetration into concrete, it is possible to enlarge the W/B ratio and reduce the adiabatic temperature rise by mixing of metakaolin. So, it is confirmed that the durability of concrete structures is increased.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.157-165
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• 2016

It is possible to achieve high strength ranging from 40 MPa to 70 MPa in alkali-activated slag concrete (AASC), and AASC is also known to have a finer pore structure due to its high latent hydraulicity and fineness of slag cement, which makes it difficult for chloride ions to penetrate. Electrophoresis is mostly used to calculate the effective diffusion coefficient of chloride ions, and then to evaluate resistance to salt damage. Few studies have been conducted on the fixation capacity of chloride ions in AASC. For this reason, in this study the chloride fixation within the hardened paste was evaluated according to the type and the amount of alkaline activators. As a result, it was revealed that among the test specimens, the chloride fixation was greatest in the paste containing $Na_2SiO_3$. In addition, it was found that as more activator was added, a higher level of chloride fixation was observed. Through this analysis, it can be concluded that the type and the amount of alkaline activators have a high correlation with the amount of C-S-H produced.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.401-404
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• 2008

Crack is a penetration path of harmful material such as chloride ion, and causes a serious deterioration in durability. So, the characteristics of chloride penetration are investigated for the cracked flexural concrete members using high-durable materials. For these, the flexural crack of beam specimen is introduced by transverse loading. And, Rapid Chloride Penetration Test (RCPT) and Long-term chloride penetration test are carried out to compare the chloride penetration depth. From test results when crack is happened, the chloride penetration resistance of the durable member was superior than that of the normal member. Blast furnace slag concrete member has a excellent chloride penetration resistance in long-term chloride penetration test.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.481-490
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• 2012

Evaluation of chloride penetration is very important, because induced chloride ion causes corrosion in embedded steel. Diffusion coefficient obtained from rapid chloride penetration test is currently used, however this method cannot provide a correct prediction of chloride content since it shows only ion migration velocity in electrical field. Apparent diffusion coefficient of chloride ion based on simple Fick's Law can provide a total chloride penetration magnitude to engineers. This study proposes an analysis technique to predict chloride penetration using apparent diffusion coefficient of chloride ion from neural network (NN) algorithm and time-dependent diffusion phenomena. For this work, thirty mix proportions with the related diffusion coefficients are studied. The components of mix proportions such as w/b ratio, unit content of cement, slag, fly ash, silica fume, and fine/coarse aggregate are selected as neurons, then learning for apparent diffusion coefficient is trained. Considering time-dependent diffusion coefficient based on Fick's Law, the technique for chloride penetration analysis is proposed. The applicability of the technique is verified through test results from short, long term submerged test, and field investigations. The proposed technique can be improved through NN learning-training based on the acquisition of various mix proportions and the related diffusion coefficients of chloride ion.

• Korean Chemical Engineering Research
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• v.48 no.5
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• pp.643-648
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• 2010

Production of biodiesel from soybean oil catalyzed by Lewis acidic ionic liquids(ILs) containing metal chloride salts was investigated in this study. Metal chloride salts, such as $SnCl_2$, $ZnCl_2$, $AlCl_3$, $FeCl_3$ and CuCl, were screened for oil transesterification in the range of 363-423 K. Among these metal chlorides, tin chloride showed particularly high catalytic property for the oil transesterification. Similarly, among these Lewis acidic ionic liquid catalysts, $[Me_3NC_2H_4OH]Cl-2SnCl_2$ resulted in a high fatty acid methyl esters(FAMEs) content of 91.1% under the following reaction conditions: 403 K, 14 h, and a molar ratio of 1:12:0.9 (oil:methanol:catalyst). Unlike the pure tin chloride catalysts, Lewis acidic ILs containing tin chloride $[Me_3NC_2H_4OH]Cl-2SnCl_2$ catalyst could be recycled up to five times without any significant loss of activity by separating from the FAMEs with simple decantation. The Lewis acidity and high moisture-stability of this catalyst appeared to be responsible for the excellent catalytic performance. The effects of reaction time and the molar ratio of methanol/catalyst to oil on the FAMEs production were also studied in this work.