배합 및 시공조건의 변화에 따른 고강도 콘크리트의 특성분석

류현기 忠州大學校 2003 한국교통대학교 논문집 Vol.38 No.2

This is a paper for the experiments to analyze the properties of watertight which is generated during the course of construction of High Strength concrete structure. The result which has been analyzed on the general properties for construction condition according to the pouring time, the effect of laitance, the mechanical concrete, the properties of watertight using water proofing agent, is summarized as the following. The more increasing W/C, the more passing time the absorption content and permeability content increase with the properties of watertight. The absorption content is low in the case of mixing water proofing agent compared to the plain concrete. According to the existence and nonexistence to the removing laitance the absorption and permeability content is lower in the case of removing laitance rather than in the case of not removing laitance.

팽창재 치환율 변화에 따른 콘크리트의 팽창 특성에 관한 연구

柳顯記 충주대 산업과학기술연구소 2000 産業科學論文集 Vol.8 No.-

Recently, the expansive additives are used in construction fields in order to reduce the shrinkage cracking occured in concrete structure. Hower, the expansive additives sometimes may be over added due to insufficiency of congnition of constructor, which results the decrease of strength and over expansion. So in this study, the experments are perfomed to present the properties of concrete by varying the unit additions of expansive additives. As the results. The concrete shows a decrease of strength and a increase of cracking with the increase of unit addition of expansive additives which causes the self destrution of concrete specimens.

부순모래 置換率 變化에 따른 콘크리트의 力學的 特性分析

柳顯紀 忠州大學校 1998 한국교통대학교 논문집 Vol.33 No.2

This study aims to present the reference data in efficiency mixing design of concrete using the mixed fine aggregate of the river and crushed sand, through trial mixing. It also aims to analyse the mechanical properties and shrinkage in hardened state. By the test results, the formula of the unite water content is as follows. 1) Substitute Ratio of Crushed Sand 0% : w/c = 0.0909·F + 81.0242 2) Substitute Ratio of Crushed Sand 20% : w/c = -0.1104·F + 86.2807 3) Substitute Ratio of Crushed Sand 40% : w/c = -0.1170·F + 86.5635 And, in mechanical properties of concrete, the compressive strength of the concrete containing crushed sand compared with river sand is lower, tensile strength is higher, and bending strength is the same. Drying shrinkage is increased while the replacement ratio of crushed sand is increaded.

상아질접착제에 대한 광조사가 접착에 미치는 영향

류현옥,김기옥,김성교 대한치과보존학회 2001 Restorative Dentistry & Endodontics Vol.26 No.5

The purpose of this study was to investigate the influence of light irradiation over self-priming adhesive on dentin bonding. After acid etching the exposed dentin, a self-priming adhesive (Prime&Bond□NT dental adhesive system, Dentsply DeTrey, GmbH, Konstanz, Germany) was applied and light irradiation was done for 20 sec with regular intensity (600 mW/㎠) in group I and for 3 sec with ultra-high intensity (1930 mW/㎠) in group III. No light irradiation was done over self-priming adhesive in groups II and IV. Composite resin was added on the self-priming adhesive and irradiated for 40 sec with regular intensity (600 mW/㎠) in groups I and II and for 3 sec with ultra-high intensity (1930 mW/㎠) in groups III and IV. To see the effect of light curing time on dentin bonding, another 3 group specimens were prepared. Without light-irradiation over self-priming adhesive, added composite resin was irradiated for 3, 6, or 12 sec with ultra-high intensity light. After bonded specimens were stored in 37℃ distilled water for 24 hours, shear bond strength were measured using a universal testing machine (4202, Instron, Instron Co., U.S.A.) and fractured surfaces were examined under a stereomicroscope (SZ-PT Olympus, Japan) . Statistical analysis were done with one-way, two-way ANOVA and chi-square test. The results were as follows: 1.The shear bond strengths from the groups irradiated over self-priming adhesive were significantly higher than those from the groups without irradiation (p<0.05). 2.There was no significant shear bond strength difference between regular intensity light irradiation groups and ultra-high intensity ones (p>0.05). 3. There was no significant shear bond strength difference among various irradiation time groups with ultra-high intensity ones (p>0.05). 4.In stereomicroscopic examination of fractured surfaces, adhesive-cohesive mixed failure mode was mostly seen in all groups, and there was no significant difference in failure mode among groups (p>0.05) . Key words : Light irradiation, Self-priming adhesive, Dentin bonding, Shear bond strength

증점제를 이용한 일반강도 고유동 콘크리트의 특성에 관한 연구

류현기 忠州大學校 1999 한국교통대학교 논문집 Vol.34 No.2

Recently, great efforts and investment have been ceaselessly made in oder to accomplish economical production by applying new methods like minimanization of man-power into construction field, because there have been increasingly the avoidance of 3D works, on the decrese of skilled labors and old age of skilled labors. AS above situation, high fluidity concrete has been spotlight in construction field. Accordingly, in this study, from the standpoint of view for developing the high fluidity concrete that compacting is not reguired within the range of 210~300kg/cm2 of compressive strength, we have been focused on the development and practical of compressive strength, we have been focused on the development and practical using of high-fluidity concrete with viscosity agent, which can prevent segregation resulting from flowing highly normal concrete by applying superplasticizer. The main agent and flyash replacement is combi ned, high-fluidity concrete with high quality can be accomplished.

鑛山廢棄物을 骨材로 이용한 시멘트 모르터에 관한 實驗的 硏究

柳顯紀 忠州大學校 1996 한국교통대학교 논문집 Vol.31 No.2

To use the waste in complementing the insufficient amounts of natural aggregate resource the provides the great effect. So, this study analyzes and experiments the research on the actual condition, the productive amounts of mine--waste and the possibility to be applied, focused on mines in Chung-buk area as a basic research in using mine-waste for the aggregate of concrete. The results are as follow : In analyzing and experimenting mortar and concrete application of mine-waste, by suggesting the evaluation method called the index of flow, strength, we could evaluate the possibility for aggregate. But even though physical characteristics in some mine were good, it was evaluated as the faulty result by this method in some mines.

충남대학교 공업기술 계열 교사 연수 프로그램에 대한 만족도 분석

류창열,최유현,김판욱,김기수,김태훈,이창훈 忠南大學校 工業敎育硏究所 2005 論文集 Vol.27 No.1

The purpose of this study was to analyze the educated teachers' satisfaction of the in-service education programs of industrial technical and technology teachers in Chungnam National University. This study was carried out through survey to accomplish the purpose. The number of questionnaires collected was 86. This study used the SPSS program to conduct a descriptive analysis of the data. The results of this study were as follows: (1) The satisfaction about 'teachers' participation', 'utilization of audiovisual materials and instruments' and 'level of professor and lecture' was relatively high. (2) The satisfaction about 'environments of in-service education programs', 'evaluation of achievement', and 'efficacy of lectures' was relatively low.

잔골재율 변화에 따른 콘크리트의 특성분석

柳顯紀 충주대 2004 産業科學論文集 Vol.12 No.-

The volume of aggregate in a concrete mixture occupies approximately 70~80 percent of a total volume. Especially, Fine aggregate is important to mix design because it has a lot of effects on a concrete quality. Accordingly, this research that consults list of references mix and sets a standard looking for a proper S/a made a study of a concrete dynamical quality change according to the fluctuation of S/a.

단위 팽창재량 및 양생방법에 따른 팽창 콘크리트의 특성에 관한 연구

柳顯紀 충주대 2000 한국교통대학교 논문집 Vol.35 No.2

When the expansive additives are used in concrete to reduce the shrinkage cracking, it shows variable properties with the curing method and curing temperature.Therefore, in this study, the experiments are perfomed to present the expansion of concrete by varying the unit additions of expansive additives and the curing method.According to the test results, the order of expansion by curing method, which is caused by hydration heat of concrete, is follows; curing at air after curing at water for 7 days > curing at air Concrete using expansive additives shows that high expansion is place with rise of temperature.

산업부산물을 이용한 고성능 콘크리트의 특성에 관한 연구

류현기,윤승조 충주대 산업과학기술연구소 1999 産業科學論文集 Vol.7 No.2

This is study intended to develop the high performance concrete by using Fly Ash, Silica Fume and Expansive Additives in order to prevent the crack from caused by dry-shrinkage and get the economical efficiency. Form the test results, the optimum addition rate based on the fluidity, segregation resistibility, strength and length-change test can be achieved at 5% of Expansive Additives in the combination of 15:5 (Fly Ash : Silica Fume).