• Journal of the Korean Ceramic Society
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• 제11권1호
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• pp.10-18
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• 1974

The hydration at $23^{\circ}C$ between $Ca(OH)_2$ and siliceous materials with various compositions of silica gel and quartz were studied in paste state, and also diatomite was empolyed as another form of silica. The effect of the structural state of silica on the pozzolanic reactivity was investigated by X-ray, DTA, electron microscopy, and chemical analysis. The results obtained were as follows. (1) The molar ratio of $Ca(OH)_2$ to silica gel(C/Sg) being changed in 0.49, 0.81 and 1.22, the free $Ca(OH)_2$ was disappeared within six hours, three days and two weeks respectively and ill-crystallized CSH(I) was formed. However, in the case fo molar ratio of C/Sg=2.45, almost lime was remained uncombinedly after twenty four weeks yet. (2) Though the molar ratio C/Sg of diatomite was 0.71, the hydration was stabilized at three weeks and the result exhibited very peculiar characteristics from silica gel. (3) Pozzolanic reactivity of quartz was negligible, but $\alpha$-cristobalite in diatomite showed appreciable reactivity. (4) The thermal curves showed the exothermic peaks in the range 830 to $930^{\circ}C$ and lower broad peaks at high temperature in the initial steps of hydration, transfered to lower temperature with sharp peaks by proceeding of hydration. (5) The samples containing more silica gel exhibited higher pozzolanic reactivity and martar strength, but the diatomite gave remarkable result for them and they were matched to the strength development rate.

• Journal of the Korean Society of Food Science and Nutrition
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• 제24권2호
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• pp.286-292
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• 1995

Proximate composition, dimension, water uptake and volume increase rates of three cultivars of Korean kidney beans, Pink(PKB), Red(RKB) and White(WKB) were compared. Significant differences in the proximate composition and calorie were not observed among samples. Hull removed samples showed the lowest ash content and the highest calorie. The rates of water uptake increased as the soaking temperature increased from 10~4$0^{\circ}C$. The moisture gain of the kidney beans during soaking showed a similar pattern to volume increase. Water uptake and volume increase rates were in the decreasing order of PKB, RKB and WKB. Moisture and volume gains held a linear relation with the square root of soaking time regardless soaking temperatures. The activation energies of water uptake and volume increase were 3033~3087 and 3077~ 3161 kcal/mole, respectively. The log time to reach a fixed moisture content showed a linear relation with soaking temperature regardless soaking temperatures. The z-values calculated from weight and volume changes decreased in proportions to the increase of hydration. The z-values of weight and volume to reach 50% hydration were 50.5~56.6$^{\circ}C$ and 48.4~61.2$^{\circ}C$, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.669-672
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• 2008

To analyze possibility for high performance concrete that massively displaces blast furnace slag, this study analyzed the characteristics of concrete by blast furnace slag displacement rate changes, and the results are summarized as follows. Firstly, as for fresh concrete characteristics, flow tended to increase and air amount decreased with increase in blast furnace slag displacement rate, and settling time was shown delayed. As for hardened concrete characteristics, in conditions where blast furnace slag displacement rate increased up to 50%, the compressive strength decreased below OPC at early age, however at age 28 days, its level was no less than that of OPC, and as for temperature rise by simple insulation, it decreased as displacement rate increased at early stage of hydration, but in the latter stage, hydration progress slowed down and hydration heat increased.

• Journal of the Korean Recycled Construction Resources Institute
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• 제11권1호
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• pp.9-15
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• 2023

The cement is a typical CO₂ emission industry. Manufacturing process improvements and increased use of alternative materials are needed to reduce energy consumption and CO₂ emissions. This study confirmed the basic characteristics of cement hydration by sintering CAF at low temperature as a CO₂ adsorbent material. For the hydration product of the synthetic CAF, crystal phase analysis, porosity, and structural images were confirmed, and the compressive strength was measured. The replacement rate of SCAF was 10, 20, and 100 %, and the compressive strength tended to decrease as the replacement rate increased. In addition, when the SCAF substitution rate is 100 %, the hydration products of the early age are calcium aluminum oxide hydrate (Ca₃Al₂O₆ x H₂O) and calcium iron hydroxide (Ca₃Fe(OH)₁₂), and at substitution rates of 10 and 20 %, CAF compounds other than general cement hydrates brownmillerite was observed. As for the porosity, the pore size increased and the porosity increased with the increase of the replacement ratio. As a result of this study, CAF manufactured by low-temperature sintering seems to be difficult to use alone and general curing for utilization as a CO₂ adsorbing material.

• The Korean Journal of Ceramics
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• 제3권4호
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• pp.235-238
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• 1997

Basic properties of new cement pastes based on the system $CaO-Al_2O_3-P_O_5-H_2O$were studied Phosphoric acid solutions and calcium dialuminate clinkers synthesized by the hydration-burning method were used for liquid and powder components of the paste, respectively Variation in the compositions of the paste was achieved by changing the liquid/powder ratio and the concentration of phosphoric acid solution. The hardening rate of the paste was so largely affected by the amount of phosphoric acid that hardening was inhibited with the low-concentrated solution but was explosively accelerated with the high-concentrated solution. The phosphoric acid solutions of concentration of 45~50% and the liquid/powder ratio of 0.5~1.5 were favoured for the high early-strength cement paste with the reasonable hardening rate and high strength. The binding phase of hardened paste was the dense amorphous gel of the system $CaO-Al_2O_3-P_O_5-H_2O$. in which the unreacted calcium dialuminate grains were embeded.

• Journal of Pharmaceutical Investigation
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• 제26권2호
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• pp.99-103
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• 1996

Effects of glycerin and PEG 400 in donor and receptor solutions upon skin permeation of drug were investigated. Deoxycortisone was used as a model compound. In vitro skin permeation study with freshly excised hairless mouse skin was performed and the steady-state skin permeation rates of the drug were determined in different fractions of glycerin or PEG 400 in donor and receptor solutions. Glycerin in donor solution didn't show any effect on the skin permeation rate of deoxycortisone. However glycerin in receptor solution showed significant effect on the skin permeation rate of the drug. In glycerin, there's a critical concentration for balancing hydration and dehydration of skin. At low concentration, less than 20 %, glycerin showed the enhancement of the flux due to the hydration effect of skin. At high concentration, more than 30 %, glycerin retard the permeation rate which might be due to the dehydration effect on the dermis layer. Since dermis has more water content than the stratum corneum, the steady state skin permeation rates were more influenced when glycerin was in receptor solution than that of in donor solution. PEG 400 aqueous solutions doesn't affect the steady state permeation rate of deoxycortisone significantly.

• Applied Biological Chemistry
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• 제33권1호
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• pp.18-23
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• 1990

Seven varieties of soybeans(Paldal, Danyeob, Jangbaek, Baegun, Jangyeob and 2 cultivars of Local 1 and Local 2) were investigated to compare the water uptake properties and volume changes during soaking in water. The hydration properties showed that the equilibrated weight increase ratio decreased as the soaking temperature raised to higher than $40^{\circ}C$, while the initial water uptake rate increased upto $80^{\circ}C$. The increase in hydration showed a linear relationship with the square root of the soaking time at $4^{\circ}{\sim}60^{\circ}C$. Local 1 was the highest in water uptake rate constant while Local 2 was the lowest. The activation energy calculated was in the range of $3,246{\sim}4,694\;cal/mole$. The Jangbaek and Local 1 were the highest and the Paldal was the lowest in the rate of volume increase. The activation energy for volume increase was in the range of $3,310{\sim}4,190\;cal/mole$. The z-values calculated from volume change was a little higher than those obtained from weight change.

• Journal of Pharmaceutical Investigation
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• 제22권1호
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• pp.41-48
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• 1992

Six common tablet disintegrants (corn starch, Avicel PH102, calcium carboxymethylcellulose, Primojel, Kollidon CL and Ac-Di-Sol) were used at the concentration of 0, 2, 4 and 6% (w/w) in salicylamide tablets made with wet granulation method. Certain physical parameters of the disintegrants (moisture sorption, hydration capacity and bulk density) were determined to evaluate their relative efficiency. The disintegration time and dissolution rate of the tablets were correlated well with the ranks of initial rate of moisture sorption for each disintegrant as follows; Ac-Di-Sol, Kollidon CL, primojel, calcium CMC, corn starch and Avicel PH102. The initial rate of moisture sorption was important for the disintegration capacity as well as hydration capacity. The effect of storage at different temperatures and relative humidity upon the tablets containing various disintegrants was evaluated in terms of tablet hardness and disintegration time. Storage at high temperature reduced the hardness substantially and retarded the disintegration of the all tablets studied. Especially, the hardness of tablets containing Kollidon CL was significantly reduced. Although the tablet hardness was decreased and the disintegration time was increased under a moderate humid condition, both of them were decreased under the severely high humid condition of 80 or 90% RH, which was due to the breakrupture of tablet matrix bonds by the excessive uptake of moisture. Therefore, the stability caused by moisture sorption should be considered, when disintegrants having high moisture sorption such as Kollidon CL, Ac-Di-Sol and Primojel were employed in the tablets containing water-labile or hygroscopic drugs.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• 제29권1호
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• pp.81-92
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• 2016

Objectives : The purpose of this study is to confirm the moisturizing effects of Herbal cosmetics containing Sinhyotakrisan(SHTL) extracts on facial skin.Methods : A total of 23 women who visited Semyung Oriental Medical Center from January 10th, 2014 to Feburary 12th, 2014 were included in the study. Provided both cosmetics containing Sinhyotakrisan extract and control products, all the subjects applied one of them to half face and another to remaining half for 4 weeks. We observed change of skin hydration, skin elasticity, skin scale in 0 week, 2 weeks, and 4weeks. Statistical anyalysis was performed by using SPSS, and statistical significance was achieved if the proability was less than 5%(p<0.05).Results : 1. After 4 weeks of using SHTL, skin hydration showed a statistically significant increase compared with using control product(p=0.011). And improvement rate also did(p=0.031). 2. After 4 weeks of using SHTL, skin elasticity showed statistically significant increase compared with using control product(p=0.025). But improvement rate didn't showed statistically significant increase(p=0.068). 3. After 4 weeks of using SHTL, skin scale showed a statistically significant decrease compared with using control product(p=0.029). And improvement rate also did(p=0.047).Conclusions : Considering the above results, herbal cosmetics containing Sinhyotakrisan extracts were effective for skin moisturizing.

• Resources Recycling
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• 제15권3호
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• pp.46-57
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• 2006

This study was carried out for the purpose of recovering the refined gypsum from waste phosphogypsum. The refined gypsum was recovered as a under product of 325 mesh wet screening followed by dehydration and hydration stage. The influence of dehydration temperature and time, dehydration rate, aging time, slurry density of hydration and sonication time on the yield and grade of gypsum were investigated. The refined gypsum of $94{\sim}96%$ grade is recovered in 95% yield by wet screening after selective dehydration and hydration process, from the phosphogypsum. For the better separation efficiency of gypsum, it is recommended to treat the phosphogypsum at the conditions of as follows; 6hr's dehydration at $140^{\circ}C$, hydration slury density of $3{\sim}10%$, hydration temperature of $20{\sim}30^{\circ}C$, hydration time of 2hr. In additions, addition of sodium citrate 0.005M and sonication of $5{\sim}10min.$ are effective for increase the recovery of gypsum. On the other hand, aging the dehydrated gypsum 16 hours or longer make decrease the recovery of gypsum remarkably.