• Journal of the Korean Ceramic Society
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• v.51 no.2
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• pp.82-87
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• 2014

Due to the revised Korean standard KS L 5201 for Ordinary Portland Cement (OPC), the use of mixed cement has grown from 5% to 10%. This study investigates the hydration behavior of $C_3A$, asit is a cement mixture that is more commonly used than granulated blast furnace slag or limestone alone. Paste samples were prepared with either granulated blast furnace slag or limestone alone. Each sample was compared with the widely used Rietveld method with a cement mixture containing blast furnace slag or limestone. The hydration behavior of $C_3A$ in each OPC sample was assessed and results were analyzed. Granulated blast furnace slag promotes a high initial level of ettringite, but as the days passed, it promotes an increase in monosulfate, leading to cracks and expansion due to the penetration of sulfates in the solution. However, when limestone is added to the mixture, a transformation of ettringite to monosulfate occurs in the presence of the $CaCO_3$ in the limestone. It is considered that this produces hemi-carbonate and mono-carbonate and thus maintains the ettringite level.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.128-131
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• 2015

Hydration of nitriles in the environmentally benign neutral conditions is the most economical and attractive way to produce amides. Substantial research works have been carried out to apply the solid metal oxides and transition metal supported catalytic systems to promote the hydration of nitriles. The most significant feature of these catalysts is the applicability to a wide range of substrates including aromatic, alicyclic, hetero-atomic, and aliphatic nitriles. These catalysts are also characterized by the easy isolation from the reaction mixture and the reusability while maintaining the high catalytic activity. This review accounts over the detailed survey of the metal oxide and solid supported metal catalysts for preparing amides from the hydration of nitriles.

• Computers and Concrete
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• v.11 no.1
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• pp.39-49
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• 2013

The use of ground fly ash in concrete can increase the risk of slump loss due to the drastic surface change of the particles after the grinding treatment and the accelerated reaction compared to the untreated ash. This study is aimed at the early age hydration and time-dependent rheology changes of cement paste containing ground fly ash. An original fly ash is ground into different fineness and the hydration of cement paste containing the ground fly ash is monitored with the ultrasound propagation method. The zeta potentials of the solid particles are measured and the changes of rheological parameters of the cement pastes with time are analyzed with a rheometer. A particle packing model is used to probe packing of the solid particles. The results show that the early age hydration of the paste is strongly promoted by replacing Portland cement with fly ash up to 30 percent (by mass), causing increase of the yield stress of the paste. The viscosity of a paste containing ground fly ash is lower than that containing the untreated ash, which is explained by the denser packing of the solid particles.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.33-39
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• 1999

This study was conducted to confirm the effect of bypass dust on the hydration and mechanical properties of the cement pastes and mortar obtained from ordinary Portland cement (OPC), OPC-slag and OPC-fly ash system. The rate of heat evolution is accelerated with the content of By-pass Dust(BD). total heat evolution increased because alkali-chlorides activated the hydration of blended cement. Compressive strength and bound water content show maximum value at 5wt% By-pass Dust(BD) on each curing time in ordinary Portland cement and slag blended cement. Ca(OH)2 content of Ordinary Portland Cement increased as the content of BD and curing time. In blended cement, the formation of Ca(OH)2 is active at early hydration stage. By pozzolanic reaction, the content of Ca(OH)2 is decreased as curing time goes by. According to the BD content stable chlorides complex of Friedel's salt (C3A·CaCl2·10H2O) is created. Due to the hydration activation effect of chlorides and alkali we observed Type II C-S-H, which developed into densest microstructure.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.61-65
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• 2008

This study, having combined and displaced blast furnace slag("BS" hereinafter) known as admixture material that delays hydration reaction with coarse particle cement("CC" hereinafter) collected in particle classification method during ordinary portland cement("OPC" hereinafter), reviewed the hydration heat characteristics affecting the concrete. To reduce hydration heat, the study plain-mixed which used 100% OPC for W/B 50% level 1, displaced CC at level 3 of 25%, 50% and 75% for OPC, and by displacing BS with admixture material at level 5 of 0%, 20%, 40%, 60% and 80% for cement(OPC+CC), experimented totally 16 batches. As a result of experiment, in the case of flow, the more CC displacement rate increased, the more it tended to decrease, and the more BS displacement rate increased, the more it decreased. Also, as for simple adiabatic temperature rise by the CC and BS displacement rates, it decreased as displacement rate increased, and particularly in the case of displaced BS of 80%, It showed temperature reduction effect of about 63% companing with plain. Compressive strength decreased in proportion to displacement rate, however strength reduction increment was shown to decrease with age progress.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.228-231
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• 2002

We report the effect of density of thin films on moisture adsorption and hydration of MgO thin film, usually used as a protective layer in AC-PDP After hydration, lots of hemispherical shaped clusters, $Mg(OH)_2$, formed on the surface of MgO thin films. However clusters formed on low-density thin films were bigger than those on high-density films. From ERD spectra, it seemed that the concentration of hydrogen was very high in the region 20 nm from the surface of MgO thin film. The low-density thin film had more hydrogen than high-density thin film. From simulation results of ERD and RBS it was found that hydration reaction also occurred in the inner part of the film. So diffusion of Mg atoms from the inner part of the film to the surface and $H_2O$ molecules from the surface to the inner part of the film is important. And because low density thin film has many short paths for diffusion of Mg atoms and $H_2O$ molecules, low-density thin film is more hydrated. So to suppress hydration of MgO thin films, high-density thin film is needed.

• Journal of the Korean Ceramic Society
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• v.45 no.11
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• pp.744-749
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• 2008

The properties of the polymer-modified mortars are influenced by the polymer film, cement hydrates and the combined structure between the organic and inorganic phases. Also, this quality of polymer modified cement strongly depend on weather condition and polymer cement ratio. To overcome this problem, polymer-modified cement were prepared by varying polymer/cement mass ratio (P/C) with $0{\sim}20%$ and constant water/cement mass ratio of 0.5. The effect of polymer on the hydration of this polymer cement is studied on different polymer cement ratio. The results showed that the polymer cement paste have increased the viscosity in addition the amount of polymer dosage and the polymers is completed resulting in a reduced degree of hydration caused by different ion elution amount. Also we know that the reactants is calcium acetate as a results of chemical reaction between acetate group in EVA which is hydrolysis in water and $Ca^{2+}$ ion during hydration of cement.

• Journal of the Korean Ceramic Society
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• v.34 no.8
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• pp.861-869
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• 1997

In order to investigate the reaction in the system of anhydrite II-blast furnace slag, the paste hydration which made up with a liquid/solid ratio of 0.45 for 1, 3, 7, 14, 28days by the addition of accelerators to 10~30wt.% slag with natural gypsum calcined for 1hour at 500/$700^{\circ}C$ was studied by combined water determination, XRD, DTA, DSC and SEM. As a result of this experiment, it was found that hydration rate was faster in the system calcined at 50$0^{\circ}C$. Therefore the anhydrite was converted to calcium sulfate dihydrate in the hydration for 1day but the slag was not almost reacted. For the gypsum calcined at $700^{\circ}C$, the hydraton rate in the system of K2SO4 addition was faster than others in the earier period, but the activated effect of the system of Al2(SO4)3 addition was regarded as the highest over 3days. As the amount of slag was increased, they dydration rate was delayed and ettringite was observed in the case of K2SO4 system. However both Al2(SO4)3 and AlK(SO4)2 systems showed calcium sulfate dhydrate only as hydrated products.

• Membrane and Water Treatment
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• v.13 no.6
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• pp.291-301
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• 2022

In this study, cement/PVDF hollow-fiber hybrid membranes were prepared via a mixed process of diffusion-induced phase separation and hydration. The presence of X-ray diffraction peaks of Ca(OH)₂, an AFt phase, an AFm phase, and C-S-H phase confirmed the hydration reaction. Good hydrophilicity was obtained. The cross-sectional and surface morphologies of the hybrid membranes showed that an asymmetric pore structure was formed. Hydration products comprising parallel plates of Ca(OH)₂, fibrous ettringite AFt, and granulated particles AFm were obtained gradually. For the hybrid membranes cured for different time, the pore-size distribution was similar but the porosity decreased because of blocking of the hydration products. In addition, the water flux decreased with hydration time, and carbon retention was 90% after 5 h of rejection treatment. Almost all the Zn²⁺ ions were adsorbed by the hybrid membrane. The above results proved that the obtained membrane could be alternative as basement membrane for separation application.

• Journal of the Korean Society of Industry Convergence
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• v.8 no.4
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• pp.191-196
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• 2005

This study was carried out to investigate the heat storage/release characteristics of the thermochemical reaction of the calcined dolomite with the packed bed shape experimental apparatus for development of chemical heat pump system. In the present study, it was found that MgO of the calcined dolomite was not hydrated during the hydration process under the experimental conditions. Therefore, the MgO of the calcined dolomite can be regard as an inert material. As a result, it was found that all of CaO packed kept the reaction temperature of about $510^{\circ}C$ through the entire part of the bed. The dehydration reaction was incurred first at the wall side area as the supplied heat was transferred through the wall side into the packed bed. As a result of the temperature and concentration spread, the reaction was completed at the wall side progressed into the center.