• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.6
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• pp.266-273
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• 2011

Foamed glass was fabricated by using glass powder and foaming agents. For the glass powder, we used sodalime glass which's manufactured by using refused coal ore obtained as by-product from Dogye coal mine in Samcheok. And for the foaming agents, we used Calcium carbonate, Calcium phosphate and powder of shale type refused coal ore itself which has high content of carbon materials. We additionally used liquid binder for forming, and mixed together. And we formed rectangular shape and treated $800^{\circ}C$ for 20 min in an electrical furnace. The various kinds of foam glass samples were fabricated according to the kinds of foaming agents. The physical properties of samples, as specific gravity and compressive strength, were measured. Pore structure of each samples were investigated too. Foam glass with specific gravity of 0.4~0.7 and compressive strength of 30~72 kg/$cm^2$. Especially we get satisfying foam glass sample with low specific gravity of 0.47 and high compressive strength of 72 kg/$cm^2$ by the use of liquid calcium phosphate as foaming agent. It also had small and even shape of pore structure. Therefore, it is concluded that refused coal ore can be used for raw materials to manufacture secondary glass products such as a foamed glass panel for construction and industrial materials.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.2
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• pp.70-74
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• 2009

Effect of the processing variables on the formation of $Pb(Sc_{1/2}Nb_{1/2})O_3$(hereafter PSN) thin layers prepared on Pt(111)/Ti/$SiO_2$/Si substrates using the sol-gel and the spin coating method has been studied. After each deposition, the coated films were heated at $370^{\circ}C$ for 5 min. Then they were finally sintered at temperature range of $600{\sim}700^{\circ}C$ by RTA(rapid thermal annealing). The final multilayered films showed a (111) preferred orientation. On a while, the layer-by-layer crystallization of multilayered amorphous thin films without the intermediate heating exhibited a (100) preferred orientation. In case of heat treatment in the tube furnace with the heating rate of $4^{\circ}C/min$, (100) and (111) oriented thin layers were formed simultaneously. The microstructure of the deposited films were dense and crack-free with thickness of 300nm, irrespective of the processing variables.

• International Commerce and Information Review
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• v.19 no.3
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• pp.83-105
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• 2017

I tried to analyze export relation of influence in Chinese H beam(common steel), Hot Rolled Steel(common steel), Plate(common steel) which could be influenced immediately by China's cancellation of the export rebate of value added tax in 2010 through the statistic methods such as cointegration, Granger causality, impulse response and variance decomposition. In the first period they mutually influenced each other in export to Korea but in the second period, this relation of influence was lessoned. Due to production expansion of Hot Rolled Steel(common steel), Plate(common steel) in Korea, the change of import trend, the market change of steel users' industries and China's expedient export of boron steel to Korea, mutual influence among these products was greatly declined. Ever since Hyundai Steel's production expansion involving blast furnace facilities, there is need for the industry to concentrate on developing new markets for its facilities' output in Korea. Therefore, Korea's steel industry desperately needs strength of de-jure standards such as unique quality standards and related certifications, efficient distribution management, as well as export promotion strategy through its global trading network to effectively address its structural supply-demand imbalances.

• Journal of the Korea Concrete Institute
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• v.16 no.3 s.81
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• pp.319-326
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• 2004

This paper investigates the effect of the concrete containing mineral admixtures(pozzolanic materials such as fly-ash, ground granulated blast-furnace slag, silica fume and meta kaolin) on the resistance properties to chloride ion invasion. The purposed testing procedure was applied to the concrete replaced mineral admixtures for 3${\~}$4 replacement ratios under water-binder ratios ranged from 0.40 to 0.55. For the electro-migration test, Tang and Nilsson's method was used to estimate the diffusion coefficient of chloride ion. As a results, the water-binder ratios, kinds of mineral admixtures and replacement ratios, water curing periods had a great effect on the diffusion coefficient of chloride ion, and the optimal replacement ratios had a limitation for each mineral admixtures. Also, the use of mineral admixtures by mass(replacement of OPC) enhance the resistance ability against chloride penetration compared with the plain concrete. The compressive strength was shown related to the diffusion coefficient of chloride ion, the compressive strength increases with the diffusion coefficient of chloride ion decreasing. Below the 50 MPa, the variation of diffusion coefficient of concrete replaced mineral admixtures was bigger than that of plain concrete.

• Journal of the Korea Concrete Institute
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• v.16 no.3 s.81
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• pp.407-414
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• 2004

The purpose of this study is to evaluate the ability to resist chloride ions penetration of the concrete structure under marine environment in south-east asia especially. In this study, high strength concrete(HSC) with various combination of ordinary portland cement(OPC), blast-furnace slag(SG) and silica fume(SF) are cured 23 and $35^{\circ}C$ considering the site weather, and are cured in water for 3, 7 or 56 days respectively. And to investigate the fundamental properties and the resistance of chloride penetration of various HSC, setting time, slump flow, compressive strength, void and ASTM C 1202 test were conducted. Test results show that the compressive strength of HSC is similar regardless of SG replacement ratio and total charge passed of chloride is the smallest at 40% replacement of SG. The compressive strength of G4FS HSC is, besides, outstandingly high at early age compare with other HSC, but the compressive strength of G4F HSC, which is vary according to curing temperature and condition, most high at the age after 7 days. Total passed charge of HSC get larger in the order G4FS

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.3
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• pp.247-254
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• 2014

The present study prepared lightweight foam-soil concrete mixtures classified into three groups. Considering the sustainablility, workability, and compressive strength development of such concrete, high-volume supplementary cementitious materials (SCMs) were used as follows: 20% cement, 15% fly ash, and 65% ground granulated blast-furnace slag. As main test parameters selected for achieving the compressive strength of 1MPa and dry density of $1,000kg/m^3$, the unit solid content (dredged soil and binder) ranged between 900 and $1,807kg/m^3$, and soil-to-binder ratio varied between 3.0 and 7.0. Test results revealed that the flow of the lightweight foam-soil concrete tended to decrease with the increase of unit soil content. The compressive strength of such concrete increased with the increase with the unit binder content, whereas it decreased as soil-to-binder ratio increased, indicating that the compressive strength can be formulated as a function of its dry density and soil-to-binder ratio.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.2
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• pp.114-119
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• 2013

The present study tested 5 concrete mixes to develop reliable mixing proportions for the sustainable alkali-activated(AA) foamed concrete as a thermal insulation material for the floor heating system of buildings. The AA binder used was composed of 73.5% ground granulated blast-furnace slag, 15% fly ash, 5% calcium hydroxide, and 6.5% sodium silicate. As a main variable, the unit binder content varied from $325kg/m^3$ to $425kg/m^3$ at a space of $25kg/m^3$. The test results revealed that AA foamed concrete has considerable potential for practical applications when the unit binder content is close to $375kg/m^3$, which achieves the minimum quality requirements specified in KS F 4039 and ensures economic efficiency. In addition, lifecycle assessment demonstrated the reduction in the environmental impact profiles of all specimens relative to typical ordinary portland cement foamed concrete as follows: 99% for photochemical oxidation potential, 87~89% for global warming potential, 78~82% for abiotic depletion, and 70~75% for both acidification potential and human toxicity.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.36-42
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• 2018

GGBFS(Ground Granulated Blast Furnace Slag)-replacement is very effective for improving resistance to chloride attack and this can induce a long service life for RC(Reinforced Concrete) structures exposed to chlorides. In the work, the design parameters such as cover depth, surface chloride content, critical chloride content, and replacement ratio of GGBFS are considered, and optimum replacement ratio of GGBFS are derived with intended service life. The changes of surface chloride content and cover depth show 3.16~3.38 and 3.02~3.34 times of service life variation, which are most influencing parameters. Critical chloride content shows 1.53~1.57 times of service life variation regardless of w/b(Water to Binder) ratios. In the case of surface chloride content $18.0kg/m^3$, the most severe condition, cover depth over 70 mm and GGBFS replacement ratio over 42% are required with concrete containing w/b ratio under 0.42 for 100 years of intended service life. The condition of $13.0kg/m^3$, GGBFS replacement over 35% is required. For reasonable durability design, quantitative exterior condition and critical chloride content should be determined, and the criteria in Domestic Specification is evaluated to be conservative.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.2
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• pp.246-265
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• 1996

After adjusting glazed surface of laminate veneer porcelain by reduction in the clinical procedure, an additional polishing procedure is required to smoothen the roughened surface by reduction, as it is difficult to glaze it again in the furnace. In this study, four kinds of laminate veneer porcelain were ground with diamond points as done in the clinical procedure. The adjusted porcelain surface was polished with Durawhite stone, Ceramiste points, Exa cerapol, Porcelain polishing wheel, Diamond polishing paste. The degree of surface roughness was evaluated with SEM and profilometer at each step, The self glazed surface and the glazed surface with glazing powder were compared with the polished surface and surface roughness of four kinds of laminate veneer porcelain according to the polishing method and step were obserbed. The following results were obtained : 1. There was no difference in the average surface roughness Ra value and the surface roughness obserbed under SEM according to the polishing methods and steps used, among the four kinds of laminate veneer porcelain including Colorlogic, Exelco, Vintage, and Vitadur alpha product. 2. Due to porosities, the surface in the course of polishing by polishing instruments was rougher than the glazed surface, evaluated with a SEM. 3. Insta-Glaze diamond polishing paste has no statistical difference with self glazed group 1, although it has a lower value in average surface roughness Ra value. 4. Group 2 which was glazed with galzing powder was lowest in view of SEM, but it revealed higher surface roughness Ra value than group 1, the glazed surface and group 8, polished by diamond polishing paste, due to surface waveness. 5. Proper surface smoothness could not be in the surface roughness analysis of SEM and profilometer by Shofu laminate polishing kit composed of Diamond point, Durawhite stone and Ceramiste points. Based on the results of this study, the following conclusions can be drawn. We obtain low surface roughness than glazed surface by polishing instruments, but not perfect results clinically. In order to obtain a perfect clinical result or a surface smoothness comparable to glazed porcelain there is a need for further improvement of porcelain materials, condensa-tion techniques, polishing instruments and polishing methods. Furthermore card should be taken not to breakdown the glazed surface during the clinical and laboratory procedure.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.5
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• pp.596-605
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• 2003

Statement of problem : IPS Empress2 system was developed and used in prosthodontic treatment, but the cost of ingot is expensive for wide application. Purpose : This study was to investigate the possibility on recycling of IPS Empress 2 ceramic for wide application of IPS Empress 2 ceramic in prosthodontic treatment. Material and Method : 1st, 2nd and 3rd pressed disc-shaped($10{\times}1.5mm$) IPS Empress 2 specimens were made with IPS Empress ingot(200, Ivoclar, Liechtenstein) and pressing furnace(IPS Empress EP 500, Ivoclar, Liechtenstein). Vicker's surface hardness and fracture toughness, acid resistance, and pressing accuracy of IPS Empress 2 ceramic were measured and analyzed. Surface hardness was measured by microhardness tester(MTX 70. Matsuzawa, Japan), before and after surface treatment with 0.5% hydrofluoric acid and carbonic acid(Coca cola) for evaluation of acid resistance. Results : The surface hardness of 1st pressed specimen was the higher(5.11 GPa) than those of 2nd pressed(4.89 GPa) and 3rd pressed specimen(4.86 GPa), and the fracture toughness of 1st pressed ($1.58MPam^{1/2}$) and 2nd pressed specimen($1.51MPam^{1/2}$) were higher than that of 3rd pressed specimen($1.39MPam^{1/2}$). The changes of surface hardness of 1st, 2nd, and 3rd pressed specimens after treatment with fluoric acid were 0.17, 0.06, 0.05 (GPa) respectively, and those of 1st, 2nd, and 3rd pressed specimens after treatment with carbonic acid were 0.07, 0.00, 0.05(MPa) respectively. The pressing accuracy of 1st,2nd and 3rd specimen were 77.22%, 85.681%, and 75.05%. The pressing accuracy of 2nd pressed specimen was higher than that of the 3rd specimen. Conclusion : The changes of physical properties according to recycling of IPS Empress 2 from this study were insignificant. Therefore the possibility of recycling of IPS Empress 2 can be suggested from the results.