• Title, Summary, Keyword: chlorides

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Prediction of Chloride Profile considering Binding of Chlorides in Cement Matrix

  • Song, Ha-Won;Lee, Chang-Hong;Ann, Ki Yong
    • Corrosion Science and Technology
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    • v.8 no.2
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    • pp.81-88
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    • 2009
  • Chloride induced corrosion of steel reinforcement inside concrete is a major concern for concrete structures exposed to a marine environment. It is well known that transport of chloride ions in concrete occurs mainly through ionic/molecular diffusion, as a gradient of chloride concentration in the concrete pore solution is set. In the process of chloride transport, a portion of chlorides are bound in cement matrix then to be removed in the pore solution, and thus only the rest of chlorides which are not bound (i.e. free chlorides) leads the ingress of chlorides. However, since the measurement of free/bound chloride content is much susceptible to environmental conditions, chloride profiles expressed in total chlorides are evaluated to use in many studies In this study, the capacity of chloride binding in cement matrix was monitored for 150 days and then quantified using the Langmuir isotherm to determine the portions of free chlorides and bound chlorides at given total chlorides and the redistribution of free chlorides. Then, the diffusion of chloride ion in concrete was modeled by considering the binding capacity for the prediction of chloride profiles with the redistribution. The predicted chloride profiles were compared to those obtained from conventional model. It was found that the prediction of chloride profiles obtained by the model has shown slower diffusion than those by the conventional ones. This reflects that the prediction by total chloride may overestimate the ingress of chlorides by neglecting the redistribution of free chlorides caused by the binding capacity of cement matrix. From the evaluation, it is also shown that the service life prediction using the free chloride redistribution model needs different expression for the chloride threshold level which is expressed by the total chlorides in the conventional diffusion model.

Properties on the penetration of airborne chlorides to the surface roughness of concrete (콘크리트의 표면거칠기에 따른 비래염분 침투 특성)

  • Lee, Jong-Suk;Choi, Won-Sung;Kim, Sung-Wook;Lee, Jang-Hwa
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.273-276
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    • 2006
  • Airborne chlorides is moved to inland by sea wind and attach to the surface of concrete then penetrated into concrete. In addition, concrete structures are greatly affected by salt attack primarily due to airborne chlorides like it can be seen through the corrosion of rebar. Therefore, it is important to review the relationship among airborne, surface and penetrated chlorides. In this study, airborne, surface and penetrated chlorides were examined in terms of surface roughness of concrete. The results showed that penetrated and surface chlorides have close relationship with surface roughness of concrete.

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Measurement of Evaporation Rates for Lanthanum and Neodymium Chlorides

  • Kwon, S.W.;Lee, Y.S.;Jung, J.H.;Chang, J.H.;Kim, S.H.;Lee, S.J.
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • pp.74-74
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    • 2017
  • Electrorefining is a key step in pyroprocessing. The electrorefining process is generally composed of two recovery steps - the deposit of uranium onto a solid cathode and the recovery of the remaining uranium and TRU elements simultaneously by a liquid cadmium cathode. Uranium deposit recovered from the solid cathode is a dendritic powder. It is necessary to separate the adhered salt from the deposits prior to the consolidation of uranium deposit. The adhered salt is composed of lithium, potassium, uranium, and rare earth chlorides. Distillation process was employed for the cathode processing. One of the operation methods is distillation of the salt at low temperature ($900^{\circ}C$), and then melting of the deposit at high temperature to avoid a backward reaction. For the development of the salt distiller, the distillation behavior of the low vapor pressure chlorides should be studied. Rare earth chlorides in the adhered salt of uranium deposits have relatively low vapor pressures compared to the process salt (LiCl-KCl). In this study, the evaporation rates of the lanthanum and neodymium chlorides were measured for the salt separation from electrorefiner uranium deposits in the temperature range of $825{\sim}910^{\circ}C$. The evaporation rate of both chlorides increased with an increasing templerature. The evaporation rate of lanthanum chloride varied from 0.12 to $1.68g/cm^2/h$. Neodymium chloride was more volatile than lanthanum chloride. The evaporation rate of neodymium chloride varied from 0.20 to $4.55g/cm^2/h$. The evaporation rate of both chlorides are more than $1g/cm^2/h$ at $900^{\circ}C$. Even though the evaporation rates of both chlorides were less than that of the process salt, the contents of the lanthanide chlorides were small in the adhered salt. Therefore it can be concluded that $900^{\circ}C$ is suitable for the operation temperature of the salt distiller.

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Penetration Properties of Airborne Chlorides on Concrete Exposed in Marine Environment (해안환경에 노출된 콘크리트의 비래염분 침투 특성)

  • Lee, Jong-Suk;An, Gi-Hong
    • Journal of the Korea Concrete Institute
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    • v.24 no.5
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    • pp.553-558
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    • 2012
  • Airborne chlorides are transported to inland by sea wind to be attached to seashore concrete structure surface then penetrated into concrete structure members. Since the surface attached chloride amount are dependent on the amount of airborne chlorides, the prediction of distribution of airborne chlorides is important information in preventing chloride corrosion problems in seashore concrete structures. The prediction of surface chloride amount from airborne chlorides environment is extremely difficult than concrete directly in contact with seawater. In addition, their penetrating tendency is different from that of concrete immersed in seawater. In this study, properties of surface and penetrated chlorides under airborne chlorides environment are investigated. Concrete specimens were manufactured and exposed to marine environment for 3 years. The specimens were analyzed at the time durations of 1, 2, and 3 years to check surface chloride amount to penetrated chloride depth. The results revealed that there were certain differences according to surface roughness of concrete and with and without washing effect due to rainfalls. The evaluation results showed that penetrated chlorides depend on amount of airborne chlorides and duration of exposure. In addition, a notable tendency of having deeper chloride penetration and higher chloride content in concrete members under long-term exposure was observed.

Photochemical and Thermal Solvolysis of Picolyl Chlorides

  • Shim Sang Chul;Choi Seung Ju
    • Bulletin of the Korean Chemical Society
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    • v.3 no.1
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    • pp.30-33
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    • 1982
  • Photochemical and thermal solvolysis of 2,3,4-picolyl chlorides (2,3,4-PC) were studied in amine solvents and the results were correlated with the electronic structures calculated by PPP-SCF-MO CI method. Activation parameters show that the thermal solvolysis of PC is $S_N2$ type rcaction. The rates of thermal reaction in pyridine or t-butylamine solvent decrease in the order of 2-PC > 3-PC > 4-PC. These results are consistent with the predictions based on the electron densities of picolyl chlorides. In photosolvolysis, the same products as those of thermal reactions were obtained. The results indicate that photochemical solvolysis undergoes through heterolytic cleavage. Relative quantum yields of photosolvolysis of 2,3,4-picolyl chlorides in t-butylamine solvent were determined to be 0.73, 1, and 0.50 respectively. These results are in good agreement with the electron densities of the excited triplet state of picolyl chlorides.

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Solvolyses of N-Methyl-N-phenylcarbamoyl Chlorides with Electron Acceptor Substituents in A Queous Binary Mixtures

  • Gu, In Seon;An, Seon Gyeong;Yang, Yeol;Go, Han Jung;Choe, Mun Ho;Lee, Ik Chun
    • Bulletin of the Korean Chemical Society
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    • v.22 no.8
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    • pp.842-846
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    • 2001
  • Solvolyses of N-methyl-N-phenylcarbamoyl chlorides in aqueous binary mixtures of acetone, ethanol, methanol and in water, D2O, and 50% D2O-CH3OD are investigated at 25.0 $^{\circ}C.$ The Grunwald-Winstein plots of first-ord er rate constants for N-methyl-N-phenylcarbamoyl chlorides with YCl (based on 2-adamantyl chloride) show a dispersion phenomenon. The ring parameter (I) has been shown to give considerable improvement when it is added as an hI term to the original Grunwald-Winstein and extended Grunwald-Winstein correlations for the solvolyses of N-methyl-N-phenylcarbamoyl chlorides. This study has shown that the magnitude of l, m and h values associated with a change of solvent composition is able to predict the dissociative SN2 transition state. The kinetic solvent isotope effects determined in deuterated water are consistent with the proposed mechanism of the general base catalyzed and/or a dissociative SN2 mechanism channel for N-methyl-N-phenylcarbamoyl chlorides solvolyses.

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Studies on Ion Permselective Charged Membranes (III) (Ion 선택투과성과하전막에 관한 연구(III))

  • 박수민
    • Textile Science and Engineering
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    • v.29 no.1
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    • pp.51-56
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    • 1992
  • The permeation behavior of tetraalkylammonium chlorides and C.I.Basic Red 18 was investigated. The permeability coefficient, P against the concentration of the upstream salt solution, Cu was quite different between tetraalkylammonium chlorides and C. I. Basic Red 18. Tetraalkylammonium chlorides gave an usual pattern of P on C. The small value of P due to Donnan exclusion in the low concentration range increases with the increase of Cu. On the contrary, C. I. Basic Red 18 gave a decrease of P with dye concentration. The result of tetraalkylammonium chlorides can be interpreted by means of TMS theory. The effective charged group concentration in the membranes was found to depend on the ionic species. The greater the Stokes radius the larger the effective charge density of the membranes. The result of C. I. Basic Red 18 can be analyzed in terms of the dual mode interaction between polymer and dye. The difference of the permeation behavior between tetraalkylammo-nium chlorides and C. I. Basic Red 18 is attributed to the higher affinity of the larger dye ion.

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Effects of Various Salts on the Reheating Behavior of Retrograded Rice Starch and Cooked Rice

  • Han, Sung-Hee;Kim, Bo-Reum;Lee, Seog-Won;Rhee, Chul
    • Preventive Nutrition and Food Science
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    • v.16 no.2
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    • pp.157-164
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    • 2011
  • The influence of sodium salts and chlorides at various concentrations (0.05, 0.10, 0.50, and 1.00%) on the reheating behavior of retrograded rice starch and cooked rice was investigated. The degree of gelatinization of the all retrograded rice starch gels and the cooked rice containing sodium salts and chlorides increased after reheating compared to the starches without salt. Gelatinization also showed an increasing trend as the concentration of sodium salts and chlorides increased. The increase of gelatinization after reheating the samples containing sodium salts and chlorides was greater than 38.0%. The reheated retrograded rice starch and cooked rice containing $Na_3PO_4$ showed the lowest set back value and retrogradation rate constant. Among all the samples, the cooked sample containing $Na_3PO_4$ showed the highest increment of gelatinization after reheating. Also, this same sample showed the lowest retrogradation degree.

Synthesis of Polyphenylene-1,2,4-Owadiazoles and Quinone Polymer by the Reactions of Tere- and Iso-Phthalohydroxamoyl Chlorides with Bisdipolarophiles

  • Suck-Ju Hong
    • Journal of the Korean Chemical Society
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    • v.15 no.3
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    • pp.121-125
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    • 1971
  • Tere-and Isophthalohydroxamoyl chlorides were condensed with 1, 4-benzoquinone to afford quinone type polymer with the oxidation of the ring structure. Similarly, tere-and isophthalohydroxamoyl chlorides were condensed with tere-and isophthaldioximes and terephthalonitrile to give crystalline polyphenylene-1,2,4-oxadiazoles, among which the reaction product of terephthalohydroxamoyl chloride with terephthalonitrile in xylene afforded the highest crystallinity.

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A Study on the Corrosion Characteristics of Steel Reinforcements Induced by Internal Chlorides in Concrete (콘크리트 내부염소이온에 의한 철근의 부식특성에 관한 연구)

  • 오병환;장승엽;신용석;차수원;김광수
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.197-202
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    • 1998
  • The corrosion of steel reinforcements in concrete is of much concern in recent years. The mechanism of corrosion, however, is not clear yet. This study is focused on the corrosion of steel induced by internal chlorides in concrete at early ages. To examine the critical concentration of steel, half-cell potential, chemical composition of expressed pore solutions of mortars and rate of corrosion area were observed with respect to additions of chlorides, types of binders, water-binders ratio.

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