• The Journal of Korean Academy of Prosthodontics
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• v.25 no.1
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• pp.303-316
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• 1987

The purpose f this study was to evaluate the effect of resin film thickness on the tensile bond strength and to compare the tensile bond strengths of 4 differently treated metal surfaces. For the experiment, seventy metal specimens were cast with Verabond and divided into I, II, III, groups. The metal specimens in group I were electrolytically etched and cemented with Panavia under finger pressure. Cement film thickness was regulated with metal spacers. The metal specimens in Group II were treated by 4 methods, such as electrolytic etching method, salt-roughened method, EZ-oxisor method , chemical etching method and cemented with Panavia. In group III, electrolytically etched metal specimens were cemented with Hy-Bond. The etched surface of metal specimens and the cement film thickness were examined under the scanning electron microscope. Results were as follows; 1. The tensile bond strength showed no significant difference between $30{\mu}m,\;80{\mu}m,\;130{\mu}m$ film thicknessspecimens. 2. There was no significant difference in the tensile bond strength between the 4 differently treated metal specimens. 3. The tensile bond strength showed significant difference between Panavia and Hy-Bond. 4. Scanning electron microscope photograph revealed that tile interdendritic eutectic was removed in electrolytically etched metal surfaces hilt even dendritic arm was removed in Chemically etched metal surfaces. 5. The metal surfaces which were air-abraded with $50{\mu}m$ aluminum oxide showed roughness and small crack on scanning electron microscope photograph.

• Journal of the Korean Geosynthetics Society
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• v.16 no.1
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• pp.19-29
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• 2017

The effects of synthetic fibers, cement content, and sand content on the flexural performance of cement-clay-sand mixtures has been evaluated through a flexural performance test with a third-point loading. Beam specimens for the flexural performance test were fabricated with a various amount of cement, sand, and synthetic fibers. Two types of fibers, PVA (Polyvinyl alcohol) and PP (Polypropylene) fibers, were employed in the test. The test results have exhibited that the factors considered in the test have significant effects on the flexural performance of the mixtures in several aspects. The flexural performance of the mixtures has been improved if the mixtures were reinforced with synthetic fibers. The flexural strength and the flexural toughness of the mixtures has been increased as the fiber content was increased. A multiple linear regression analysis has been performed to evaluate the effect of fiber content, cement dosage, and sand content on the flexural performance of the mixtures in terms of flexural strength and flexural toughness. Cement content and sand content were estimated as important factors to have an influence on the first-crack strength and the peak strength whereas the fiber content has the most significant influence on the post-crack behavior. The first-crack strength and the ultimate strength were increased as the cement content and the sand content were increased. As the fiber content was increased, the flexural toughness was increased.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.417-421
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• 2003

The purpose of this paper is to study on the construction of roadbed with environmental friendly soil amendment agent. The special amendment agent used in this study is mainly composed of inorganic metal salts such as sodium chloride, magnesium chloride, potassium chloride, calcium chloride,, thus is friendly to the environment, and has a function of soil-cement-agent solidification. Various components of this agent weaken the negative function of humic acid and decompose humic acid itself. Then, the calcium cation of the cement can now be made contact directly to the soil surface. The project of local road demonstration of roadbed construction with special soil treatment agent was peformed in Northeast Thailand on August 1999 by the sponsor of Highway Department of Thailand. A series of field experiments including unconfined compressive strength were carried out to investigate the physical and mechanical characteristics of solidified roadbed treated by this solidifying agent. The results of this research showed that the roadbed using poor soil could be efficiently constructed by treatment of this amendment agent.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.521-526
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• 2001

Box-culvert is very important structure used almost every road construction. However this is treated very simple structure in design and construction. So many crack such as nonstructural crack has been occurred. This crack is very harmful on durability of concrete. In this study, thermal crack, one of the nonstructural crack, of box-culvert controled by using rapid-strength belite cement concrete. In this process, not only heat of hydration and thermal stress but also material mechanics properties and characteristics of durability were tested. and same model box-culvert using OPC concrete is constructed in same condition for comparison.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.1
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• pp.85-91
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• 1992

The purpose of this study was to evaluate the bonding strength between porcelain laminate and Ni-Cr alloy in the various surface treatments of the bonding faces. For this study the metal surface of specimens were treated : 1) etching only, 2) sandblasting only, and 3) sandblasting and etching. The porcelain laminate were made and bonded to the metal specimens with light curing composite resin cement. Instron testing machine was used to measure their bonding strength : and the result was obtained as follows : 1. The bonding strength of the double treatment of the sandblasting and etching group was higher than that of the single treatment of sandblasting or the etching group. 2. The bonding strength of the sand blasting group was higher than that of the etching group. 3. The debonding were mainly occurred between the Ni-Cr alloy and the composite resin cement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.165-166
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• 2018

Researches for the development of renewable energy as a fuel substitute for global warming and depletion of petroleum resources are actively being carried out. Among them, the annual growth rate of PV generation is 20.73%, which is higher than other renewable energy sources. However, the production of 1 ton of polysilicon, which is known as a raw material for solar power generation panels, generates 2 tons of waste. As the demand for PV panels increases, the problem of the treatment of polysilicon sludge is attracting attention, and studies on the utilization of polysilicon sludge are needed. Therefore, in this study, the applicability of polysilicon sludge treated as industrial waste to the lightweight panel for architectural purposes was examined.

• Restorative Dentistry and Endodontics
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• v.4 no.1
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• pp.29-34
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• 1978

The purpose of this study was to measure penetration of dye stuff(5% Methylene blue, Hematoxylin, Crystal violet and Safranin-O) on silicate cement, Adaptic, Hi-pol and unfilled resin. Each filling material was mixed on the mixing pad and the mixed material was inserted with condensation force of 500gr, 1000gr and 2000gr and without condensation force into preformed glass tube (10mm in diameter and 10mm in height). The specimen was stored in the air for 24 hours, then specimen was immersed in various dye solution (5% methylene blue, hematoxin, crystal violet and safranin-O) for different period of time (l hour and 24 hours). These dye-treated specimen was cut horizontally at the middle portion and the dye penetration in cut surface was measured. Following results were obtained. 1. Pentration of various dye was excessive in silicate cement with and without Condensation force. 2. There has been no evidence of dye penetration in unfilled resin. 3. Dye penetration occurced with in 1 hour period and the extending time didn't affect the dye penetration.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.627-635
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• 2019

Cement-asbestos slate is the main asbestos containing material. It is a product made by combining 10~20% of asbestos and cement components. Man- and weathering-induced degradation of the cement-asbestos slates makes them a source of dispersion of asbestos fibres and represents a priority cause of concern. When the asbestos enters the human body, it causes cellular damage or deformation, and is not discharged well in vitro, and has been proven to cause diseases such as lung cancer, asbestos, malignant mesothelioma and pleural thickening. The International Agency for Research on Cancer (IARC) has designated asbestos as a group 1 carcinogen. Currently, most of these slats are disposed in a designated landfill, but the landfill capacity is approaching its limit, and there is a potential risk of exposure to the external environment even if it is land-filled. Therefore, this study aimed to exam the possibility of detoxification of asbestos-containing slate by using exothermic reaction and heat treatment. Cement-asbestos slate from the asbestos removal site was used for this experiment. Exothermic catalysts such as calcium chloride(CaCl₂), magnesium chloride(MgCl₂), sodium hydroxide(NaOH), sodium silicate(Na₂SiO₃), kaolin[Al₂Si₂O₅(OH)₄)], and talc[Mg₃Si₄O₁₀(OH)₂] were used. Six catalysts were applied to the cement-asbestos slate, respectively and then analyzed using TG-DTA. Based on the TG-DTA results, the heat treatment temperature for cement-asbestos slate transformation was determined at 750℃. XRD, SEM-EDS and TEM-EDS analyses were performed on the samples after the six catalysts applied to the slate and heat-treated at 750℃ for 2 hours. It was confirmed that chrysotile[Mg₃Si₂O₅(OH₅)] in the cement-asbestos slate was transformed into forsterite (Mg₂SiO₄) by catalysts and heat treatment. In addition, the change in the shape of minerals was observed by applying a physical force to the slate and the heat treated slate after coating catalysts. As a result, the chrysotile in the cement-asbestos slate maintained fibrous form, but the cement-asbestos slate after heat treatment of applying catalyst was broken into non-fibrous form. Therefore, this study shows the possibility to safely verify the complete transformation of asbestos minerals in this catalyst- and temperature-induced process.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.462-471
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• 2008

The quality control for DCM is based on the unconfined compressive strength of laboratory treated soils, the cement contents, setting and checking the strength of in-situ treated soils. Also the strength of in-situ is checked mainly by the core boring. In case of large size construction, it might be considered the distribution of DCM strength data as normal distribution, so it might be employed a statistical method to evaluate DCM strength easily. In Japan, it has been established correlation between the strength of laboratory treated soils, the strength of in-suit treated soil and the design strength. Also It has been employed domestically the correlation suggested by Japan. But the correlation, so called $\lambda$(ratio in the strength of laboratory treated soils and the in-suit) and $\gamma$(ratio in the strength of in-suit and the design strength), might be far different with the domestic due to different DCM system and soil properties. so it might be restrictive to use domestically. Therefore in this paper, It is presented correlation between the strength of laboratory treated soils and in-suit treated soil to be employed domestically by evaluating $\lambda$ based on the domestic in-suit illustrations.

• Restorative Dentistry and Endodontics
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• v.46 no.4
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• pp.54.1-54.10
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• 2021

Objectives: The purpose of this study was to quantify phase transformation after hydrofluoric acid (HF) etching at various concentrations on the surface of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP), and to evaluate changes in bonding strength before and after thermal cycling. Materials and Methods: A group whose Y-TZP surface was treated with tribochemical silica abrasion (TS) was used as the control. Y-TZP specimens from each experimental group were etched with 5%, 10%, 20%, and 40% HF solutions at room temperature for 10 minutes. First, to quantify the phase transformation, Y-TZP specimens (n = 5) treated with TS, 5%, 10%, 20% and 40% HF solutions were subjected to X-ray diffraction. Second, to evaluate the change in bond strength before and after thermal cycling, zirconia primer and MDP-containing resin cement were sequentially applied to the Y-TZP specimen. After 5,000 thermal cycles for half of the Y-TZP specimens, shear bond strength was measured for all experimental groups (n = 10). Results: The monoclinic phase content in the 40% HF-treated group was higher than that of the 5%, 10%, and 20% HF-treated groups, but lower than that of TS-treated group (p < 0.05). The 40% HF-treated group showed significantly higher bonding strength than the TS, 5%, and 10% HF-treated groups, even after thermal cycling (p < 0.05). Conclusions: Through this experiment, the group treated with SiO₂ containing air-borne abrasion on the Y-TZP surface showed higher phase transformation and higher reduction in bonding strength after thermal cycling compared to the group treated with high concentration HF.