• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.537-540
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• 2006

Over the past few decades, a considerable number of studies on the durability of concrete have been carried out extensively. A lot of improvements have been achieved especially in modeling of ionic flows. However, the majority of these researches have not dealt with the chloride binding isotherm based on the mechanism, although chloride binding capacity can significantly impact on the total service life of concrete under marine environment. The purpose of this study is to develop the model of chloride binding isotherm based on the individual mechanism. It is well known that chlorides ions in concrete can be present; free chlorides dissolved in the pore solution, chemical bound chlorides reacted with the hydration compounds of cement, and physical bound attracted to the surface of C-S-H grains. First, sub-model for water soluble chloride content is suggested as a function of pore solution and degree of saturation. Second, chemical model is suggested separately to estimate the response of binding capacity due to C-S-H and Friedel's salt. Finally, physical bound chloride content is estimated to consider a surface area of C-S-H nano-grains and the distance limited by the Van der Waals force. The new model of chloride binding isotherm suggested in this study is based on their intrinsic binding mechanisms and hydration reaction of concrete. Accordingly, it is possible to characterize chloride binding isotherm at the arbitrary stage of hydration time and arbitrary location from the surface of concrete. Comparative study with experimental data of published literature is accomplished to validity this model.

• Analytical Science and Technology
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• v.25 no.1
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• pp.33-38
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• 2012

Despite the importance of chloride binding, it is very difficult to measure the binding capacity, in particular, for the concrete body in an existing structure: in fact, the measurement procedure for chloride binding is much influenced by the environmental condition such as temperature, fineness of sample and pore water extraction techniques. The present study concerns the quantification of the binding capacity of chloride ions in concrete using the X-ray diffraction (XRD) technique. Once the binding isotherm of chlorides was determined by the Langmuir isotherm, as a function of the W/C, curing age and binder type, the generation of bound chlorides (i.e. Friedel's salt) was simultaneously ensured by the XRD technique. The amount of bound chloride was then determined by analyzing the peak intensity for the bound chlorides in the XRD curve. It was found that an increase in the curing age and a decrease in the W/C resulted in an increase in the binding capacity.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.464-466
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• 2010

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.133-142
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• 2008

This paper studies the early-aged chloride binding capacity of various blended concretes including OPC(ordinary Portland cement), PFA(pulversied fly ash), GGBFS(ground granulated blast furnace slag) and SF(silica fume) cement paste. Cement pastes with 0.4 of a free water/binder ratio were cast with chloride admixed in mixing water, which ranged from 0.1 to 3.0% by weight of cement and different replacement ratios for the PFA, GGBFS and SF were used. The content of chloride in each paste was measured using water extraction method after 7 days curing. It was found that the chloride binding capacity strongly depends on binder type, replacement ratio and total chloride content. An increase in total chloride results in a decrease in the chloride binding, because of the restriction of the binding capacity of cement matrix. For the pastes containing maximum level of PFA(30%) and GGBFS(60%) replacement in this study, the chloride binding capacity was lower than those of OPC paste, and an increase in SF resulted in decreased chloride binding, which are ascribed to a latent hydration of pozzolanic materials and a fall in the pH of the pore solution, respectively. The chloride binding capacity at 7 days shows that the order of the resistance to chloride-induced corrosion is 30%PFA > 10%SF > 60%GGBFS > OPC, when chlorides are internally intruded in concrete. In addition, it is found that the binding behaviour of all binders are well described by both the Langmuir and Freundlich isotherms.

• Computers and Concrete
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• v.13 no.6
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• pp.695-707
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• 2014

This study investigated the chloride binding isotherms of various cement types, especially the contributions of C-S-H and AFm hydrates to the chloride binding isotherms were determined. Ordinary Portland cement (OPC), Modified cement (MC), Rapid-hardening Portland cement (RHC) and Low-heat Portland cement (LHC) were used. The total chloride contents and free chloride contents were analyzed by ASTM. The contents of C-S-H, AFm hydrates and Friedel's salt were determined by X-ray diffraction Rietveld (XRD Rietveld) analysis. The results showed that OPC had the highest chloride binding capacity, and, LHC had the lowest binding capacity of chloride ions. MC and RHC had very similar capacities to bind chloride ions. Experimental equations which distinguish the chemically bound chloride and physically bound chloride were formulated to determine amounts of the bound chloride basing on chloride binding capacity of hydrates.

• Journal of the Korea Concrete Institute
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• v.29 no.4
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• pp.389-397
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• 2017

Friedel's salt is an important product of chemical adsorption between cement hydrate and chloride ions because it contains chlorine in its structure. When cement reacts with water in the presence of chloride ions, the $C_3A$ phase, and $C_4AF$ phase react with chloride to produce Friedel's salt. If chloride ions penetrate into concrete from external environments, many calcium aluminate hydrates, including AFm, can bind chloride ions. It is very important, therefore, to investigate the chloride binding isotherm of $C_3A$ phase, $C_4AF$ phase, and AFm phase to gain a better understanding of chloride binding in cementitious materials. Meanwhile, the adsorption isotherm can provide us with the fundamental information for the understanding of adsorption process. The experimental results of the isotherm can supply not only the quantitative knowledge of the cement-Friedel's salt system, but also the mechanism of adsorption and the properties of their interactions. The purpose of this study is to explore the time dependant behaviors of chloride ions adsorption with $C_3A$, $C_4AF$ and AFm phases. The chloride adsorption isotherm was depicted with Langmuir isotherm and the adsorption capacity was low in terms of the stoichiometric point of view. However, the chloride adsorption of AFm phase was depicted with Freundlich isotherm and the value was very low. Since the amount of the adsorption was governed by temperature, the affecting parameters of isotherm were expressed as a function of temperature.

• Journal of the Korean Society of Clothing and Textiles
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• v.27 no.5
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• pp.523-523
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• 2003

The change of interactions of anionic surfactants, sodium dodecyl sulfate(SDS) and sodium tetradecyl sulfate(575) in the presence of electrolytes, to the chitosan-based polyelectrolyte(sol＇n and gel phase) were studied. The chitosan gel used in this study were crosslinked with epichlorohydrin(ECH). Binding isotherms were determined by potentiometric technique using a surfactant ion selective solid-state electrode and the results were represented by using the sequence generating function(SGF) method. The results of binding isotherm were shown comparatively high cooperativity. The addition of electrolytes in the chitosan/SDS system resulted in a shift of the binding to higher free surfactant concentration because of screen effect by the electrolytes. Degree of binding of chitosan gel was higher than that of chitosan sol＇n. And also a conformational phase transition of the chitosan gel in the presence of electrolytes has been investigated.

• Journal of the Korean Society of Clothing and Textiles
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• v.27 no.5
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• pp.524-532
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• 2003

The change of interactions of anionic surfactants, sodium dodecyl sulfate(SDS) and sodium tetradecyl sulfate(575) in the presence of electrolytes, to the chitosan-based polyelectrolyte(sol＇n and gel phase) were studied. The chitosan gel used in this study were crosslinked with epichlorohydrin(ECH). Binding isotherms were determined by potentiometric technique using a surfactant ion selective solid-state electrode and the results were represented by using the sequence generating function(SGF) method. The results of binding isotherm were shown comparatively high cooperativity. The addition of electrolytes in the chitosan/SDS system resulted in a shift of the binding to higher free surfactant concentration because of screen effect by the electrolytes. Degree of binding of chitosan gel was higher than that of chitosan sol＇n. And also a conformational phase transition of the chitosan gel in the presence of electrolytes has been investigated.

• Textile Coloration and Finishing
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• v.24 no.4
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• pp.239-246
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• 2012

The binding isotherms of ionic dyes with Poly(vinylpyrrolidone) in aqueous solution were determined by the dynamic dialysis technique. The shape of the isotherms of cationic dye, C. I. Basic Red 18 with poly(vinlypyrrolidone) showed a partition type. It suggests that the binding involves a non-cooperative mode. Isotherms of an anion dye, a synthesized dye by coupling of diazotized m-trifluoromethylaniline with 2-naphthol-6-sulfonic acid, were sigmoid type and showed multimode interaction. The results were interpreted by the McGhee von Hippel theory. The thermodynamic parameters for the complex formation of the dyes-polymer were calculated from their temperature dependences of the intrinsic binding constant.

• Biotechnology and Bioprocess Engineering:BBE
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• v.5 no.6
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• pp.431-435
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• 2000

The goal of this research is to compare the metal binding characteristics of an anoxic selector activated sludge system and a conventional activated sludge system. Metal biosorption by biomass harvested from experimental systems was determined by a series of batch experiments. Heavy metals studied in this research were zinc, cadmium, and nickel. The sorption isotherm showed that the selector sludge had significantly higher sorption capacity than did the control sludge. Metal biosorption behavior closely followed a Freundlich isotherm model for equilibrium concentrations. ECP contents of biomass estimated by alkali extraction technique showed that ECP levels in the selector sludge significantly higher than that in the sludge harvested from the conventional system, indicating that the higher metal sorption capacity of selector sludge may be due to the selection of the ECP-producing bacteria (i.e., Zoogloea sp.) by the selector system.