• Title/Summary/Keyword: 내구특성

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The Discoloration Characteristics of Orpiment used as Traditional Yellow Mineral Pigments in Painting Cultural Properties (채색문화재에 적용된 전통 황색 광물안료 석황의 채색 특성)

  • Jin Young Do
    • Korean Journal of Mineralogy and Petrology
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    • v.36 no.1
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    • pp.1-17
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    • 2023
  • On painting cultural properties to which Orpiment, a traditional yellow mineral pigment, is applied, the color's degeneration is frequently observed. To identify the cause of the degeneration, this study takes a look into orpiment and the various pigments that are mixed into it (Lead White, Lead Red, and Cinnabar) in powder and painting state. The pigment was mixed with Argyo glue and then applied to korean traditional paper and silk. Considering the possibility that alum causes the discoloration, it was applied to the specimen. With a UV tester, the powders and the painted specimens were subjected to a light resistance test in three phases (96 hour). Color changes were measured with a colorimeter and minerals, chemical composition and structural changes were analysed by XRD, SEM/EDS and Raman spectrometers. While the color change of pure Orpiment powder according to the light resistance test was small, the colored specimen became darker. The color change was large in the Orpiment colored on the silk and in the alum-treated specimen. In Orpiment powder was produced white arsenolite as altered orpiment after UV test. In the mixed powder of Orpiment and Lead White were detected only the constituent minerals of Orpiment and Lead White, and no altered substances were produced. Whereas after the UV test, orpiment and arsenolite, which were altered substances of orpiment, and the constituent minerals of Lead White were detected. In the case of mixing the two pigments in the powder state, darkening did not occur even by the UV test. However, the specimens colored with the mixed powder were darkened by the UV test. The color change of Orpiment was different depending on the mixed pigment and base material. The color change was greater in the case of alum treatment than in the case without alum treatment, and it was found that alum also had an influence on the color change of Orpiment.

A Experimental Study on the Ready-mixed Shotcrete Using Granulated Blast Furnace Slag (고로슬래그 미분말을 혼입한 레디믹스트 숏크리트의 현장적용성에 관한 실험적 연구)

  • Choi, Hee-Sup;Kim, Dong-Min;Jang, Pil-Sung;Seo, Sin-Seuk
    • Journal of the Korean Geotechnical Society
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    • v.25 no.6
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    • pp.31-45
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    • 2009
  • The aim of this study is to evaluate the applicability of Granulated Blast Furnace Slag to the development of the Powdered Ready-mixed Shotcrete. First of all, after accomplishing SEM analysis and Leaching Test, the laboratory and field experiments for evaluating the utility of Granulated Blast Furnace Slag were performed. As a result of SEM and Leaching test, the environmental stability was confirmed. That is, non-detection of harmful lists and dense shotcrete structure result from mixing Granulated Blast Furnace Slag. As a result of lab. and field test, Blast Furnace Slag is superior to Plain Batch in improving strength and durability. And it will be able to improve to some extent the problem caused by the delayed reaction of existing Granulated Blast Furnace Slag with alkali activated material. Also the proper amount of Granulated Blast Furnace Slag is estimated to be under 30%. Finally, it is possible that Granulated Blast Furnace Slag can apply to economical recycling and development of the Ready-mixed Shotcrete for its price is only about 5% of Silica-finne's price.

Structural Behavior of Rib Reinforced Mg-Si Aluminum Alloy lighting Pole (리브보강 Al-Mg-Si계 가로등 등주의 구조적 거동)

  • Nam, Jeong-Hun;Joo, Hyung-Joong;Kim, Young-Ho;Yoon, Soon-Jong
    • Composites Research
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    • v.21 no.6
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    • pp.8-14
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    • 2008
  • Lighting system of road is an essential structure used for the safety of pedestrians and vehicles. Most of the lighting pole is made with steel which is vulnerable under corrosive environment. To overcome such corrosion problems, stainless steel and iron steel are used, but they are usually manufactured by hand which is not efficient. Due to their high strength and stiffness, when there is car collision with the lighting pole structure the safety of driver may not be ensured. Hence, the development of new-type lighting pole system which is easy to adjust the right on the road, lengthen the service life, and reduce the maintenance, is necessary. Lighting pole made with aluminum alloy is high in strength per unit weight, is strong against corrosive environment, and is easy to construct due to flexibility and right weight. But, because the strength and stiffness of the material is lower than that of steel, the structural safety and serviceability of the system can be a problem. To mitigate the structural problem associated with conventional lighting pole system, experimental investigation is conducted on the conventional lighting pole and rib reinforced aluminum alloy lighting pole, respectively. By comparison of results, it was found that the rib reinforced Mg-Si aluminum alloy lighting pole is efficiently applicable to the lighting pole system of road.

Revision of Repair Materials Performance Requirement for Concrete Structures (콘크리트 구조물 단면복구공사 보수재료 품질기준개선)

  • Lee, Il Keun;Kim, Ki Hwan;Kim, Hong Sam;Yun, Sung Hwan;Kim, Woo Seok
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.43 no.1
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    • pp.9-20
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    • 2023
  • For highway concrete structures, the deterioration of the structure is accelerated due to the increase in the use of deicing materials, and sectional repair work is being frequently carried out to restore performance. However, after the repair work, re-damage such as cracks, delamination, and poor bond performance is exhibited in the repaired sectional area. In this study, overseas repair material requirements were first analyzed, and present domestic requirements were improved repair material performance through field surveys of common concrete structures, laboratory experiments, and test construction on a disused concrete bridge. In addition, performancebased quality requirements were presented so that all materials that meet the required performance can be applied, and different test methods for each material were unified into concrete test methods for consistent test results analysis. The considered performance requirements were compression strength, bending strength, and bond strength for structural properties, and length change rate, crack resistance, thermal expansion coefficient, and elasticity coefficient were for dimensional behavior. For resistance to chloride penetration resistance and freeze-thaw resistance were presented as durability. The proposed requirements for concrete repair materials are expected to contribute to the improvement of the quality of concrete sectional repair work in Korea.

Self-Healing Property of Hardened Cement Paste (시멘트 페이스트 경화체의 self healing 특성)

  • Kim, Jae Young;Byun, Seung Ho
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.2A
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    • pp.297-304
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    • 2008
  • It is well known that cracks in concrete decrease permeability and durability of concrete because cracks enhance the penetration of water or corrosive chemicals like as chlorides, carbon dioxides, sulfates and some others. But some of cracks in hardened cements may be sealed in case of contacting water. This phenomenon is called "self healing" and it has a close relation to hydration products newly formed on surfaces of cracks. Many studies on self healing in concretes commonly showed that CSH gel has been observed on crack surfaces. And some studies have reported that calcium hydroxides and ettringite were observed as well as CSH gel on crack surfaces. This study was carried out to investigate hydration products formed by self healing process and also examine the influence of waterproof admixture for concretes on self healing of cement. As a result of XRD, DSC, SEM and EDX analysis of crack surfaces, it was found that self healing of cement was related to CSH gel, calcium hydroxides and ettringite. And waterproof admixture increased fibrous (needle-like) hydration products which were in network form. It is estimated that such fibrous products are effective for self healing process of cement system.

Stress Intensity Factor of Cracked Plates with Bonded Composite Patch by p-Convergence Based Laminated Plate Theory (p-수렴 적층 평판이론에 의한 균열판의 팻취보강후 응력확대계수 산정)

  • Woo, Kwang-Sung;Han, Sang-Hyun;Yang, Seung-Ho
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.5A
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    • pp.649-656
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    • 2008
  • The enhancement of the service life of damaged or cracked structures is a major issue for researchers and engineers. The hierarchic void element based on the integrals of Legendre polynomials is used to characterize the fracture behaviour of unpatched crack as well as repaired crack with bonded composite patches by computing the stress intensity factors and stress contours at the crack tip. Since the equivalent single layer approach is adopted in this study, the proposed element is necessary to represent a discontinuous crack part as a continuum body with zero stiffness. Thus the aspect ratio of this element to represent the crack should be extremely slender. The sensitivity of numerical solution with respect to energy release rate, displacement and stress has been tested to show the robustness of zero stiffness element as the aspect ratio is increased up to 2000. The stiffness derivative method and displacement extrapolation method have been applied to calculate the stress intensity factors of Mode I problem. It is noted that the proposed hierarchical void element can be one of alternatives to analyze the patched crack problems.

Influence of Mineral Admixtures on the Diffusion Coefficient for Chloride Ion in Concrete (광물질 혼화재가 콘크리트의 염소이온 확산계수에 미치는 영향)

  • Bae, Su-Ho;Park, Jae-Im;Lee, Kwang-Myong;Choi, Sung
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.4A
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    • pp.347-353
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    • 2009
  • The qualitative factors influencing the ingress of chloride ion into concrete are water-binder (W/B) ratio, cement type, age, chloride ion concentration of given environment, wet and dry conditions, etc. Thus, an objective of this experimental research is to investigate the effects of cement types and environmental conditions on the chloride ion diffusion characteristics in concrete through the chloride ion diffusion test. For this purpose, the diffusion coefficients for chloride ion in concrete with three types of cement such as ordinary portland cement (OPC), binary blended cement (BBC), and ternary blended cement (TBC), were measured for the concrete specimens with W/B ratios of 32%, 38%, and 43%, respectively. The diffusion coefficients for chloride ion were also measured for the concrete specimens with W/B ratio of 43%, which were subjected to standard curing and field exposure conditions. It was observed from the test results that the resistance against chloride ion penetration increased with decreasing W/B ratio and those of BBC and TBC concretes were greater than that of OPC concrete. Therefore, it was revealed that the use of these cements containing mineral admixtures is required to extend the service life of RC structures exposed to chloride environment. On the other hand, it was noted that the resistance against chloride ion penetration of field exposure test specimens was slightly lower than that of standard curing test specimens due to the penetration of chloride ion under the irregular ambient temperature, splash of wave, and cycle of wet and dry.

Fatigue Behavior of Steel-Concrete Composite Bridge Deck with Perfobond Rib Shear Connector (유공판재형 전단연결재를 갖는 강-콘크리트 합성바닥판의 피로거동에 관한 연구)

  • Kyung, Kab Soo;Lee, Seung Yong;Jeong, Youn Ju;Kwon, Soon Cheol
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.1A
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    • pp.71-80
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    • 2010
  • Bridge deck is directly influenced by environment and vehicle load, it is easily damaged so that it requires an appropriate repair and retrofit. Therefore, developing a bridge deck with high durability is necessary in order to minimize the maintenance of bridge deck and use it to its design life. In this study, static test was carried out to evaluate a fatigue capacity of steel-concrete composite deck, which was newly developed by supplementing problems of existing reinforced concrete deck. Based on results from the static test, fatigue load was decided, and fatigue test was conducted under the constant amplitude repeated load. From the fatigue tests, the S-N curve regarding principle structural details of composite deck was made, and characteristics of fatigue behavior was estimated by comparing and evaluating it with fatigue design criteria. In addition, fatigue design guideline was presented. As a result, it is found that each structural details of composite deck proposed by this study, such as upper flange of corrugated steel plate and middle section of it, shear connector and lower flange of corrugated steel plate, is satisfying the fatigue strength.

A Study of Control for 3 Phase BLDC Motor using Control Methodology of DC Motor (직류전동기 제어기법을 적용한 3상 BLDC 모터 제어에 관한 연구)

  • Jin-Man Kim;Taek-Kun Nam
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.29 no.6
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    • pp.704-711
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    • 2023
  • This paper discusses the control method of BLDC(Brushless Direct Current) motor that has similar electrical characteristics with DC motor but has improved its lifespan and reliability. The BLDC motor can improve durability and speed stability by using rotor position information to eliminate commutators that require mechanical contact with DC motors. In this study, a controller for a DC motor was designed based on the fact that the current in the windings of a BLDC motor is a square-wave current like the current flowing in the armature of a DC motor. Next, the designed controller was applied to a 3-phase BLDC motor to confirm the effectiveness of the controller. In detail, a single-phase DC motor with electrical parameter values of a three-phase BLDC motor was modeled and a PI controller for motor speed control was designed by applying the root locus method to the derived system. The speed control simulation of the DC motor was performed to confirm the validity of the controller, and the same controller was applied to the speed control of the 3-phase BLDC motor implemented in MATLAB. From the simulation, similar results of the DC motor were obtained in the 3 phase BLDC motor and confirmed the usefulness of the proposed control scheme.

Basic Characteristics and Field Demonstration Test of Ground Granulated Blast Furnace Slag using CO2 Fixed Desulfurized Gypsum (CO2 고정 탈황석고를 사용한 고로슬래그 미분말의 특성 및 현장실증)

  • Chang-Woo Lee;Hoon-Guk Choi;Sung-Kwan Seo;Jong-Ho Park
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.12 no.3
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    • pp.281-289
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    • 2024
  • In this study, CO2-immobilized desulfurized gypsum(CFDG) was applied to ground granulated blast furnace slag to examine the basic properties of mortar and concrete, and to evaluate its responsiveness through field demonstration test. CFDG had a relatively circular composition compared to desulfurized gypsum(DG), and its main components were CaO 47.6 % and SO3 22.1 %. As a result of mortar and concrete tests, the flow tended to increase and the compressive strength was at the same level. In addition, the target properties of concrete for application to farm roads, which were a slump of 120±25 mm and a compressive strength of 24 MPa, were satisfied with a slump of 135 mm and a compressive strength of 42.1 MPa at 28 days. In February 2024, an on-site demonstration of a farm road was conducted in Seongmun-myeon, Dangjin-si, and as a result of reviewing the compressive strength according to curing conditions, the physical properties and durability of unhardened concrete, the target results were satisfied, expanding the use of CFDG by applying fine powder of blast furnace slag and carbon reduction can be expected.