• Title/Summary/Keyword: 점성저항

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Ability to Resist Chloride Ion Penetration and Dry Shrinkage Evaluation of Magnesium Phosphate Ceramics (인산마그네슘 세라믹의 염소 이온 투과 저항성 및 길이변화 특성에 관한 성능 평가)

  • Ko, Jeong-Won;Yang, Wan-Hee;Park, Dong-Cheol
    • Journal of the Korea Institute of Building Construction
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    • v.17 no.4
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    • pp.341-348
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    • 2017
  • The performance degradation of concrete pavement by winter deicer is very serious in Korea, and its maintenance and rehabilitation brings a high expense. Therefore, a suitable method for rehabilitation of such concrete pavement and repair material of proper performance are required. In this study, the properties of compressive strength, ability to resist chloride ion penetration, and properties of dry shrinkage of magnesium phosphate ceramics were assessed to evaluate its applicability as a repair material for concrete pavement in Korea. As a result, the mortar flow showed a normal level of 190 mm, but the viscosity was high and the self-flow ability was poor. The setting time was 12 minutes, leading very rapid-hardening, and thus a prompt work was required. The compressive strength of mortar was 38.4MPa in 2 hours, 73.8MPa in 24 hours, and 111.0MPa in 28 days, showing a significant level. As a result of the test to chloride ion penetration resistance, mortar showed 143 Coulombs, and concrete showed 172.6 Coulombs, which fell under very low level. The drying shrinkage of MPC concrete in 40 days was below $60{\times}10-6$, and comparing with normal cement concrete, it showed the level below 1/10 of other concrete to secure an excellent volume stability. As above, magnesium phosphate ceramics has excellent strength performance, chloride ion penetration resistance, and volume stability, and this in the future shall be used in construction under the consideration of working time or workability, requiring further improvement for such performance.

Suggestion of Segregation Evaluation Method based on Evaluation Index for Segregation(EIS) (재료분리 평가정수(EIS)에 의한 재료분리 평가법의 제안)

  • Han, Cheon-Goo;Kim, Gi-Cheol;Park, Byung-Kwan
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.923-926
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    • 2008
  • Currently more high flow and high performance concrete is used for construction of buildings in the world. However, when high flow and high performance concrete put high performance water reducing agent in quantity to improve flow, it has a negative effect on concrete structures since segregation arises from it though flow will be improved. There are naked-eye observation, coarse aggregate washing test, L Flow test for permeation among reinforcing rods and measurement of viscosity to judge concrete segregation resistance. However, it is difficult to apply them to practical affairs since they are very complicated and troublesome. Therefore, the study analyzed EIS dividing slump flow value into slump value, how to valuate concrete segregation resistance more easily, on the basis of the existing reference materials to propose EIS. As the results, in the event of high flow concrete, it is desirable that EIS value is prescribed to be less than 2.5 at the time of managing segregation. Also, at the time of prescribing EIS with performance, it is judged that it is desirable to manage segregation as less than 2.2 (Grade 1), 2.2$\sim$2.4 (Grade 2) and more than 2.6 (Grade 3).

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Evaluation of the Effect of PE Wax on Asphalt Binder Properties (PE Wax를 첨가한 아스팔트 바인더의 물리적 특성)

  • Kim, Boo-Il;Jeon, Sung-Il;Lee, Moon-Sup;Cho, Yoon-Ho
    • International Journal of Highway Engineering
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    • v.8 no.4 s.30
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    • pp.101-113
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    • 2006
  • Generally, asphalt binder modifier increases the viscosity at high temperature as well as at mixing and paving temperature, so that higher temperature is required to produce the hot-mix asphalt. Otherwise, wax is able to improve workability by means of decreasing the viscosity of asphalt binder. In this study, the effect of PE wax used to modify the asphalt binder was evaluated in laboratory. The properties of PE wax modified binder were compared with those of SBS and Crumb Rubber Modified binders. The results showed that wax type I has an effect on strengthening rut resistance as well as improving workability. However, wax type I weaken crack resistance due to making binder harder at intermediate temperature. The results also showed that wax type II has an effect on improving workability and on strengthening crack resistance due to making binder softer.

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S.D.O.F Macro-element for Interaction of Deep Foundation (단자유도 매크로요소를 이용한 깊은기초의 상호작용 모델)

  • Rha, Chang-Soon
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.21 no.4
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    • pp.347-355
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    • 2008
  • In this paper single degree of freedom macro-element model was presented to investigate the interaction between soil and the deep foundation under the lateral loads. It was made by modelling each component related to the soil-structure interaction and combining them into one piece. It enhanced the conventional method that was not able to break down the interaction components in piece due to the usage of simple spring element for interaction. A proposed macro-element classified the stress components in relation to the interaction into frictional and compressive resistance. Each component was modelled using the classical plasticity theory, and finally combined in parallel. An example study was carried out using the proposed macro-element for deep foundation embedded in three layered cohesive soil. It showed improved results compared to the conventional method by producing additional information of the interaction components as well as the overall behavior of foundation.

An Evaluation of Moisture Sensitivity of Asphalt Concrete Pavement Due to Aging (노화에 따른 아스팔트 콘크리트 포장의 수분민감성 평가)

  • Kim, Kyungnam;Kim, Yooseok;Kim, Nakseok
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.39 no.4
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    • pp.523-530
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    • 2019
  • Pavement distress and traffic accidents are caused by pot-hole. In addition, direct and indirect damages of road users are increasing, such as loss of life due to personal injury and damage to vehicles. Generally, the asphalt concrete pavements are continuously aging from the production process to the terminal performance period. Aging causes stripping due to cracks and moisture penetration and weakening the pavement structure to induce pot-hole. In this study, adhesion performance and moisture sensitivity were evaluated according to aging degree in order to investigate the effect of aging on asphalt pavement. As a result of the study, the viscosity of the asphalt binder was increased with aging and the bond strength of the aged was increased 2~3 times than that of the unaged. The results of accelerated aging test showed an increases in indirect tensile strength and the increase in the TSR (Tensile Strength Ratio) by 4.2~8.9 %. As a result, it is noted that the anti-stripping and adhesion performances of the aged asphalt concrete are improved compared to the unaged one under the aging conditions of asphalt binder coated on aggregates.

Evaluation of Local Erosion Characteristics of Fine-Grained Soils in the West Coast Area (서해안 세립토의 국지적 침식특성 평가)

  • Kwak, Kiseok;Lee, Juhyung;Park, Jae Hyun;Woo, Hyo Seop
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.5C
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    • pp.323-331
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    • 2006
  • It is a recent worldwide trend that erosion characteristics of soil, the resistance factor against scour, are quantified and considered in the estimation of scour depths in fine-grained soils. As part of the efforts, local erosion characteristics on fine-grained soils of the West Coast area are analyzed through scour rate experiments, where a lot of sea-crossing long-span bridges are planned and being constructed in recent years. Four sites including Incheon Bridge, Choji Bridge, Hwankyung Bridge, and Janghang area are finally selected for this study and the scour rate tests are performed using 34 undisturbed soil samples from the sites. The critical shear stresses which represent erodibility of the soil tend to be proportional to the undrained shear strength values. The relative ability of cohesive fine-grained soils to resist erosion is assumed to be higher than that of noncohesive soils. Quantified local erosion characteristics of fine-grained soils in the West Coast area are presented in forms of charts showing relationships between scour rates and shear stresses, and suggested as basic data for the estimation of scour depths and design of bridge foundations in the West Coast area.

Setting Assessment of Hogh Strength Concrete Using the Ultrasonic Pulse Velocity Monitoring (초음파 속도 모니터링에 의한 고강도 콘크리트의 응결 평가)

  • 이회근;이광명
    • Journal of the Korea Concrete Institute
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    • v.14 no.6
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    • pp.973-981
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    • 2002
  • Recently, the use of high strength concrete (HSC) has increased dramatically md however, few studies have been conducted on the early-age properties of HSC such as setting. The penetration resistance test (specified by KS F 2436) that is the standard test method for determining initial and final setting times of concrete, may not be appropriate for HSC because of the high viscosity of the mortar mixture. To address this issue, an ultrasonic pulse velocity (UPV) monitoring system was used to investigate the setting behavior of mortar and concrete. The experimental study was carried out to measure the UPV's of mortars and concretes having various water/binder ratios (W/B) and various fly ash replacement levels, during the first 24 hours of testing. Test results showed that the UPV in concrete was developed faster than that of mortar with the same W/B, and that of ordinary concrete was greater than that of fly ash concrete. Typical values of UPV were suggested that correspond to the initial and final setting times, based on following criteria: (1) the penetration resistance method; (2) the instant when the UPV begins to develop; and (3) the instant when the UPV development rate is maximum. The method and UPV monitoring device used in this study is promising for the setting assessment of concrete, particularly for HSC.

Principle of Sensor Systems by using a Quartz Crystal and Their Applications (수정진동자를 이용한 센서시스템의 원리와 응용)

  • Kim, Jong-Min;Chang, Sang-Mok;Kim, Woo-Sik
    • Korean Chemical Engineering Research
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    • v.47 no.6
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    • pp.655-668
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    • 2009
  • The principle and applications of quartz crystal sensors based on the three basic concepts for mass, viscosity, and viscoelastic changes are reviewed. In the general discussion the basic principle of quartz crystal and realization of a resonant frequency-resonant resistance diagram are described in detail. As examples of their applications, gas sensing with a carbon-coated quartz crystal, determination of the blood coagulation factor, an electrochemical analysis and crystallization analysis are reported. The possibility of developing new biosensors and chemical sensors is discussed on the basis of these results.

Finite Element Analysis of Piezocone Test II (피에조콘 시험의 유한요소 해석 II)

  • 김대규;김낙경
    • Journal of the Korean Geotechnical Society
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    • v.16 no.4
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    • pp.191-199
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    • 2000
  • In this research, the finite element analysis of piezocone penetration and dissipation tests has been conducted using the anisotropic elastoplastic-viscoplastic bounding surface model, virtual work equation, and theory of mixtures formulated in the Up[dated Lagrangian reference frame for the large deformation and finite strain nature of piezocone penetration. The formulated equations have been implemented into a finite element program. The cone resistance, excess pore water pressure, and dissipation of excess pore water pressure from the finite element analysis have been compared and investigated. An effective simulation could be performed with the use of the anisotropic and viscous soil model. The finite element formulations and the results are described in part 'I' and part 'II' respectively.

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Numerical Study on Viscous Wakes of Two-Dimensional Screens Normal to the Uniform Stream (균일유동에 수직인 2차원 스크린 후류의 점성유동에 관한 수치적 연구)

  • 강신형;전우평
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.3
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    • pp.590-598
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    • 1988
  • Viscous flows through a screen normal to an uniform flow are numerically simulated. A .kappa.-.epsilon. model is adopted for evaluation of the Reynolds stresses. The existence of a screen is regarded as extra sources in the momentum equations. The amount of extra sources is related to the resistance coefficient and the refraction coefficient of the screen. Flows are numerically simulated for various resistance coefficients and heights of the screen and Reynolds numbers. The present method has been verified to reasonably simulate viscous wakes and shear layers of the screen, for which the inviscid theory is quite limitted. As the fluids approach the screen, the velocity is reduced and the pressure is raised to satisfy the Bernoulli equation. After passing the screen, the velocity shows its minimum value at the down-stream, but static pressure is slowly recovered. A detached separation-bubble from the screen appears as the resistance coefficient is increased to a certain level. Such results are qualitatively in agreement with limitted experimental data available. The turbulent kinetic energy shows its maximum value at further down stream and decrease thereafter.