• Journal of the Korean Society of Clothing and Textiles
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• v.7 no.2
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• pp.19-25
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• 1983

The purpose of this study was to investigate the effects of laundry variables and additives on the removal of deposited calcium on the cotton fabric. Samples of calcium deposited fabric was made by treating fabric with $CaC1_2$ and $Na_2CO_3$ solution subsequently. The experimental variables were: 1) NaOH concentration ($0.0001\%$, $0.0005\%$, $0.001\%$, $0.005\%$, $0.01\%$) 2) Alkaline builders(sodium carbonate, sodium meta silicate) 3) Sequestering agents(STPP and EDTA concentration: $0.02\%$, $0.04\%$, $0.06\%$, $0.08\%$, $0.1\%$, $0.15\%$, $0.2\%$) 4) Temperatures($25\pm1^{\circ}C$, $40\pm1^{\circ}C$, $60\pm1^{\circ}C$) 5) Edge-abrasion to the removal of deposited calcium on the cotton fabric. The fabric was washed for 15 minutes in a washing machine(Model: Gold Star WP-3007) or Launder-0-meter(40$\~$45 r.p.m., Toyo Rika Instrument Inc.) and rinsed 3 times per every rinsing time. The amount of calcium deposits on the fabrics was determined by EDTA-back titration methods and edge-abrasion was evaluated by ASTM D 3886 method. The results of this study were as follows: 1) pH of surfactant solution(NaOH concentration) did not influence on the removal of deposited calcium on the cotton fabric. 2) Added alkaline builders did not influence on the removal of deposited calcium on the cotton fabric. 3) It was shown that STPP and EDTA were effective to remove deposited calcium. The removal of deposited calcium on the cotton fabric was proportionally increased with increasing concentration of STPP and EDTA. At high concentration, however, the rate was rather decreased with increasing concentration. 4) The temperature of washing solution did not influence on the removal of dedosited calcium on the cotton fabric. 5) As the removal of deposited calcium on the cotton fabric was increased, the rate of edge-abrasion of the fabric was gradually increased.

• Environmental Engineering Research
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• v.11 no.1
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• pp.54-61
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• 2006

An electron probe microanalysis (EPMA) investigation can provide quantitative and qualitative insight into the nature of the surface and bulk chemistry on solidified waste forms(SWF). The proportion of Pb in grain areas is below 0.3 wt. %, and the proportion near the border of the grain slightly increases to 0.98 wt. % but in the inter-particle areas farther from the grain, the concentration of Pb markedly increases. It is apparent that very little Pb diffuses into the tricalcium silicate($C_3S$) particles and most of the Pb exists as precipitates of sulfate, hydroxide, and carbonate in the cavity areas between $C_3S$ grains. Calcite additions on Pb-doped SWF are also observed to induce deeper incorporation of lead into the cement grains with EPMA line-analysis of cross-sections of cement grains. The line-analysis reveals the presence of $0.2{\sim}5$ weight % Pb over $5\;{\mu}m$ from cement grain boundaries. In the inter-particle areas, the ratio of Ca, Si, Al and S to Pb is relatively similar even at some distance from the grain border and the Pb (wt. %) ratio is reasonably constant throughout the whole inter-particles area. It is apparent that the enhanced development of C-S-H on addition of calcite can increasingly absorbs lead species within the silica matrix.

• Journal of The Korean Digital Architecture Interior Association
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• v.12 no.4
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• pp.59-66
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• 2012

This study is interested in identifying the effectiveness of alkali-activated fire protection material compounds including the alkali-activator such as potassium hydroxide, sodium silicate and fly ash as the fire resistant finishing materials. Also, this paper is concerned with change in compressive strength and pore structure of the alkali-activated fire protection material at high temperatures. The testing methods of fire protection materials in high temperature properties are make use of TG-DSC and mercury intrusion porosimetry measurements. This study results show that compressive strength is rapidly degraded depending on a rise of heating temperature. Porosity showed a tendency to increase irrespective of specimen types. This is due to both the outbreak of collapse of gel comprising the cement and a micro crack by heating. However, alkali-activated fire protection material composed of potassium hydroxide, sodium silicate and fly ash has the thermal stability of the slight decrease of compressive strength and porosity at high temperature. These thermal stability is caused by the ceramic binding capacity induced by alkali activation reaction by the reason of the thermal analysis result not showing the decomposition of calcium hydrate.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.127-128
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• 2022

In order to realize carbon neutrality in the international society, research on supplementary cementitious materials(SCMs) has been actively conducted as a way to reduce carbon dioxide emissions in the cement industry. However, the use of SCMs causes problems of initial hydration delay and strength reduction due to the reduction of tricalcium silicate(C3S) in the cement clinker. Therefore, in this study, the initial hydration and basic characteristics of cement mortar were confirmed by adding a C-S-H based hardening acceleration to blended cement mixed with Portland cement, blast furnace slag, fly ash, and limestone power. As a result of the heat of hydration and compressive strength test, it was confirmed that when hardening acceleration was added, the initial reactivity was high, so the heat of hydration was promoted, and the initial strength was increased. It is considered to be due to C-S-H seeding effect. Therefore, it is judged that the use of C-S-H based hardening acceleration can supplement the problem of initial hydration delay of blended cement in Korea.

• Journal of the Korean Ceramic Society
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• v.56 no.4
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• pp.403-411
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• 2019

In this work, the hydration process and cytotoxicity of lab-synthesized experimental Portland cements (EPCs) were investigated for dental applications. For this purpose, EPCs were prepared using laboratory-synthesized clinker constituents, tricalcium silicate (C₃S), dicalcium silicate (C₂S), and tricalcium aluminate (C₃A). C-A was prepared by the Pechini method, whereas C₃S and C₂S were synthesized by solid-state reactions. The phase compositions were characterized by X-ray diffraction (XRD) analysis, and the hydration process of the individual constituents and their combinations, with and without the addition of gypsum, was investigated by electrochemical impedance spectroscopy (EIS). Furthermore, four EPC compositions were prepared using the lab-synthesized C-A, C₃S, and C₂S, and their hydration processes were examined by EIS, and their cytotoxicity to HPC and HIPC cells were tested by performing an XTT assay. None of the EPCs exhibited any significant cytotoxicity for 7 days, and no significant difference was observed in the cell viabilities of ProRoot MTA and EPCs. The results indicated that all the EPCs are sufficiently biocompatible with human dental pulp cells and can be potential substitutes for commercial dental cements.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.5
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• pp.436-441
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• 2015

The chemical properties of paddy fields in Gyeonggi province were monitored every 4 years from 1999 to 2015 in order to provide basic information for soil fertility management of paddy fields. In 2015, the soil chemical properties of paddy fields were 5.9 in pH, $23g\;kg^{-1}$ in organic matter (OM), and $84mg\;kg^{-1}$ in available phosphate (Avail. $P_2O_5$). Exchangeable (Exch.) potassium (K), calcium (Ca) and magnesium (Mg) were 0.30, 5.1 and $1.3cmol_ckg^{-1}$, respectively, and available silicate (Avail. $SiO_2$) was $129mg\;kg^{-1}$. In the long-term analysis, the contents of Avail. $SiO_2$, Exch. Ca and pH of paddy soils showed increasing tendency. However, Avail. $P_2O_5$ and Exch. K tended to decrease, and there were no significant changes in the contents of OM and Exch. Mg. Paddy soil within appropriate pH range increased from 44% in 1999 to 76% in 2003, 84% in 2007, 63% in 2011, and 80% in 2015. But soil within appropriate range of Exch. Ca tended to decrease, showing 36% in 1999, 42% in 2003, 38% in 2007, 37% in 2011 and 32% in 2015. In case of Avail. $SiO_2$, soil within appropriate range increased from 14% in 1999 to 17% in 2003, 18% in 2007, 16% in 2011, and 31% in 2015. As a result, paddy fields with less in nutrient level need to be more fertilized based on soil analysis. And the application of silicate fertilizer is strongly recommended to those of paddy fields in need. Also soil management such as the cultivation of green manure crop or application of rice straw will be necessary to increase the organic matter content of paddy soil.

• Journal of the Korea Organic Resources Recycling Association
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• v.9 no.2
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• pp.101-107
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• 2001

The experiment was conducted to investigate the agricultural utility of macro-porous calcium-silicate rnineral(CellCaSi) as topsoil mixture, as well as to estimate as a soil conditioner. The bulk density of CellCaSi which is consisted of various particle sizes ranging from 1mm to 3.35mm was about $0.42g/cm^3$, and its maximum porosity was approximately 81.4%. We also investigate gerrnination rates for Cabbage and Lettuce to obtain the suitable mixing ratios of CellCaSi with topsoil. Among 4 different mixing ratios, the germination rates of ropsoil mixed with 10% of CellCaSi were 94.1% and 64.6% for Cabbage and Lettuce, respectively resulted in the mosr suitable for germination. The growth rates for Cabbage and Lettuce showed thar 10% and 20% of CellCaSi treatments signification influenced the fresh weight. To observe the adsorption capacity of CellCaSi, CellCaSi was treated with a chemical fertlizer(N:P:K=18:18:18). lncreasing the contents of N, P and K, the amounts of adsorption by CellCaSi for these element also increased. The most suitable types nutrient resources for growth condition of Cabbage, and Lettuce were Fer-1 and Fer-0.5.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.369-375
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• 2014

This study examined the changes of microstructural compositions in cement matrix according to the depth from the surface of a reinforced concrete (RC) column exposed to fire. The RC column was exposed to a standard fire for 180 minutes. After the fire test, core samples passing through the column section were obtained. Using the core samples, the remaining fractions of calcium-silicate-hydrates (C-S-H) and calcium hydroxide in cement matrix at the surface, the depth of 40 mm and 80 mm and the center (175 mm) were examined using thermal gravimetric analysis (TGA) and X-ray diffraction analysis (XRDA). Using nuclear magnetic resonance (NMR) technique, the silicate polymerization of C-S-H in cement matrix was also evaluated. The experimental results indicated that the amount of C-S-H loss at the center of column experiencing the transferred fire temperature of $236^{\circ}C$ has been underestimated as the TGA results showed the highest C-S-H contents are located at the depth of 80 mm, where the transferred fire temperature is $419^{\circ}C$. Moreover, the destruction of silicate connections at the center was observed as similar as that at the depth of 40 mm, where the transferred fire temperature was $618^{\circ}C$. This might be attributed to the temperature changes during cooling time after the fire test was neglected. Due to the relatively low thermal conductivity of concrete, the high temperature, which can affect the change of microstructure in cements, will hold longer at the center of the column than other depth.

• Restorative Dentistry and Endodontics
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• v.45 no.1
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• pp.3.1-3.10
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• 2020

Objectives: This study investigated the indirect effect of calcium-enriched mixture (CEM) cement and mineral trioxide aggregate (MTA), as 2 calcium silicate-based hydraulic cements, on human dental pulp stem cells (hDPSCs) through different dentin thicknesses. Materials and Methods: Two-chamber setups were designed to simulate indirect pulp capping (IPC). Human molars were sectioned to obtain 0.1-, 0.3-, and 0.5-mm-thick dentin discs, which were placed between the 2 chambers to simulate an IPC procedure. Then, MTA and CEM were applied on one side of the discs, while hDPSCs were cultured on the other side. After 2 weeks of incubation, the cells were removed, and cell proliferation, morphology, and attachment to the discs were evaluated under scanning electron microscopy (SEM). Energy-dispersive X-ray (EDXA) spectroscopy was performed for elemental analysis. Alkaline phosphatase (ALP) activity was assessed quantitatively. The data were analyzed using the Kruskal-Wallis and Mann-Whitney tests. Results: SEM micrographs revealed elongated cells, collagen fibers, and calcified nucleations in all samples. EDXA verified that the calcified nucleations consisted of calcium phosphate. The largest calcifications were seen in the 0.1-mm-thick dentin subgroups. There was no significant difference in ALP activity across the CEM subgroups; however, ALP activity was significantly lower in the 0.1-mm-thick dentin subgroup than in the other MTA subgroups (p < 0.05). Conclusions: The employed capping biomaterials exerted biological activity on hDPSCs, as shown by cell proliferation, morphology, and attachment and calcific precipitations, through 0.1- to 0.5-mm-thick layers of dentin. In IPC, the bioactivity of these endodontic biomaterials is probably beneficial.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.12
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• pp.25-29
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• 1972

This experiment was carried out to investigate the role of Silicon accumlated in rice plant under different conditions of light and humidity, using radioisotopes Ca-45, Mn-54, and P-32. This results obtained in are as follows; 1. Light effect is more severe in phosphate uptake by rice plant than is calcium. Amounts of phosphate uptake in light condition is six times more than in dark conditions, while that of calcium is double. 2. Change of relative humidity affects calcium absorption and transport from root to shoot. It seems not to be influenced in phosphate and manganese uptake by relative humidity. 3. More uptake of each element Ca-45, P-32, or Mn-54 was found in the rice plant applied with silicic acid. It is considered that there must be some relationship between silicon content and ion uptake in rice plant. 4. The transport ratio of nutrient from root to shoot shows a specific pattern that calcium is approximately 1.0 manganese 0.5 and phosphate 0.2 respectively.