• Title/Summary/Keyword: 수밀특성

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Watertightness and Crack Reduction Property of Concrete added Fluosilicate Salt Based Inorganic Compound for Watertight Concrete (수밀 콘크리트용 규불화염계 무기 조성물을 첨가한 콘크리트 수밀성 및 균열저감 특성)

  • Kim Da-Su;Khil Bae-Su;Choi Se-Jin;Park Min-Yong;Lee Seong-Yeon;Yeo Byung-Chul
    • Proceedings of the Korean Institute of Building Construction Conference
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    • v.y2004m10
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    • pp.33-38
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    • 2004
  • This study was performed to know watertightness and reduction effect and crack occurred by hydration heat, restraint of multiplication of hydration heat, through mechanical test, strength test and crack control test using fluosilicate salt based inorganic compound made from by-product during phosphoric acid manufacturing process. Mix proportions for experiment were modulated at 0.45 of water to cement ratio and $0.5-2.0\%$ of adding ratio of fluosilicate salt based inorganic compound. Evaluation for watertightness of concrete was carried out permeability, absorption test and porosity analysis. Effect of crack reduction was evaluated by length, drying shrinkage as well as stress change of hardened concrete at unrestraint/restraint state and also elucidated crack pattern on the concrete surface. It is ascertained that characteristics of crack resistance and watertightness for concrete was improved by an adequate addition of fluosilicate salt based inorganic compound.

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Experimental Study on Engineering Properties of Concrete Using Fluosilicates Based Composite (규불화염계 복합 조성물을 혼입한 콘크리트의 공학적 특성에 관한 실험적 연구)

  • Yang Il-Seung;Yun Hyun-Do;Kim Do-Su;Khil Bae-Su;Han Seung-Gu
    • Journal of the Korea Concrete Institute
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    • v.17 no.5 s.89
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    • pp.769-774
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    • 2005
  • Fluosilicic acid(H2SiF6) is recovered as an aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded H3PO4 or HF. Generally, fluosilicates are the salts produced by the reaction of H2SiF6 and metal salts. Addition of fluosilicates to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. This study was performed to know mechanical properties and watertightness using fluosilicates based composite made from fluosilicates and other compounds. Mix proportions for experiments were modulated at 0.45 of water to cement ratio and $0.0-2.0\%$ of adding ratio of fluosilicates based composite. Evaluation for mechanical properties of concrete was conducted to know fresh state of concrete, hardening state of concrete, and watertightness. Evaluation for watertightness of concrete was carried out permeability, absorption test and porosity analysis. In addition. Scanning Electron Microscopy(SEM) and Energy Dispersive X-Ray(EDX) used for investigating micro-structure and atomic component distributed in hardened concrete. It is ascertained that characteristics of mechanical properties and watertightness was more improved than non-added because of packing role of fluosilicates based composite and pozzolanic reaction of soluble $SiO_2$. Also, concrete added fluosilicates based composite had a tendency to delay setting time and only $0.5\%$ addition of fluosilicates based composite delayed 150 minutes compared with non-added.

Experimental Study on Soot Formation in Opposed-Flow Ethylene Diffusion Flames by Mixing DME as an Alternative Fuel (대체 연료인 DME 혼합에 의한 대향류 에틸렌 확산화염내 매연 생성에 대한 실험적 연구)

  • Yoon, Doo-Ho;Yoon, Seok-Hun;Choi, Jae-Hyuk
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.16 no.3
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    • pp.301-306
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    • 2010
  • DME(Di-Methyl Ehter, $CH_3OCH$) is currently attracting worldwide attention due to its environmentally friendly characteristics. Until now it was researched as a major alternative fuel of diesel automobile because it is a clean fuel producing low soot. Therefore, in this study, in order to investigate the effect of DME mixing on number density and size of soot particle, DME has been mixed in opposed-flow ethylene diffusion flame with the mixture ratios 5%, 14% and 30%. A laser extinction/scattering technique has been adopted to measure the volume fraction, number density, and size of soot particles. The experimental results showed that the soot concentration of mixture flames with the mixture ratios 5% and 14% produces soot more, even though that of 30% was decreased. This means that even though DME has been known to be a clean fuel for soot formation, the mixing of DME in diffusion flame of ethylene, where acetylene maintains high concentration in soot formation regions, could produce enhanced production of soot.

Effect of Air Void and Strength Characteristics with Freezing and Thawing Resistance on High Strength Concrete (고강도(高强度) 콘크리트에서 기포조직(氣泡組織) 및 강도특성(强度特性)이 연결융해저항(連結融解抵抗)에 미치는 영향(影響))

  • Kim, Saeng Bin;Moon, Je Kil;Kim, Dong Sin
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.13 no.3
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    • pp.13-24
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    • 1993
  • The influence of the bubble structure and strength characteristics on the freeze-thaw resistance of high strength concrete is investigated by the laboratory experiment. The test conditions are formed in the manner that water is continueusly supplied externally and the specimens were received severe weather actions from ordinary to significantly low temperatures. The experiments are performed in two stages. In the first stage, the relation between the durability to frost action and the bubble structure is analyzed especially with respect to the water-cement ratio and the amount of air. The AE and non-AE concrete specimens made of ordinary portland cement are used in the test. In the second stage, the non-AE concrete specimens using vibratory compaction to improve the durability to frost action, and the high watertight specimens of rapid hardening portland cement to increase their initial strength are produced and tested. The degree of watertightness of the specimens is determined by measuring the permeability of the specimens and the bubble structure of the high watertight concrete is also estimated.

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Group Ignition of Liquid Fuel Droplets Cloud (액체연료 액적군의 집단 점화)

  • 박용열;김호영
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.12
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    • pp.2376-2384
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    • 1992
  • A theoretical analysis is carried out to predict the characteristics of transient ignition phenomena for the spherical fuel droplets cloud with non-uniform droplet size and number density distribution. Numerical calculations are performed for various cases depending on the combinations of the major parameters such as ambient temperature and initial distributions of droplet size and number density. The results of present study show that the ignition delay decreases for higher ambient temperature and smaller droplet size. Droplets cloud of hollow type with outer concentrated distribution ignites most rapidly.

Atomization Characteristics of Small LRE-Injector Spray According to Injection Pressure Variation (소형 액체로켓엔진 인젝터 분무의 분사압력 변이에 따른 미립화 특성)

  • Jung, Hun;Kim, Jin-Seok;Kim, Jeong-Soo;Park, Jeong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.05a
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    • pp.125-128
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    • 2008
  • Atomization characteristics of small LRE-injector spray are investigated by using dual-mode phase Doppler anemometry (DPDA). Velocity, size, number density, and volume flux were measured at various injection pressures along the radial distance to make a close inquiry into spatial distribution characteristic of spray droplets. As the injection pressure increases, the velocity, turbulence intensity, number density, and volume flux of spray droplets become higher, whereas the droplet size ($D_{10}$ or $D_{32}$) gets smaller. Also, velocity and volume flux are proportional to Sauter mean diameter (SMD, $D_{32}$).

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Spatial Distribution Characteristics of Small LRE-injector's Spray-droplet According to the Variation of Fuel-injection Pressure (소형 액체로켓엔진 인젝터 분무의 연료분사압력 변이에 따른 액적의 공간분포 특성)

  • Jung, Hun;Kim, Jeong-Soo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.12 no.5
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    • pp.1-8
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    • 2008
  • Dual-mode Phase Doppler Anemometry (DPDA) was used to scrutinize the spatial distribution characteristics of spray emanating from a small Liquid-Rocket Engine (LRE) injector. Droplet size and velocity were measured according to the variation of injection pressure along the plane normal to the spray stream and then the spray characteristic parameters such as Arithmetic Mean Diameter (AMD), Sauter Mean Diameter (SMD), number density, span of drop size distribution, and volume flux were deduced for an investigation of spray breakup characteristics. As the injection pressure increases, the number density, span, and volume flux of spray droplets become higher, whereas the AMD gets smaller.

Early Strength and Properties of EVA Powder Modified High Strength Concrete (EVA Powder 개질 고강도 콘크리트의 초기강도 및 수밀특성)

  • Kim, Young-Ik;Sung, Chan-Yong
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 2005.10a
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    • pp.123-127
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    • 2005
  • EVA Powder modified high strength concretes were prepared by varying polymer/binder mass ratio with a constant water/binder mass ratio of 0.3. The effect of EVA powder on the slump, hydration heat, compressive and flexural strength, toughness and water absorption ratio was studied. In hydration heat test, temperature of hydration reaction displayed almost fixed level regardless of containing rate of EVA powder, but peak time of hydration reaction displayed late inclination as containing rate of powder increases. With the same water/binder mass ratio, the compressive strength and water absorption of EVA powder modified concretes decreased slightly when EVA powder was added and the flexural strength of EVA powder modified concretes rised slightly when EVA powder was added. Also, the toughness of the modified concretes can be improved markedly. The interpenetrating structure between the polymeric phase and cement hydrates formed at a $2{\sim}6%$(containing rate of EVA powder). The properties of the polymer modified concretes were influenced by the polymer film, cement hydrates and the combined structure between the organic and inorganic phases.

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An Experimental Study on Improving Water Tightness of Concrete Surface Applied High Growth Organic Crystalization Material (고성장 유기결정체의 성장 특성을 이용한 콘크리트 표층부의 수밀성 개선에 관한 연구)

  • Song Je-Young;Kang Hyo-Jin;Oh Sang-Keun
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.817-820
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    • 2004
  • Our country was much developments in change of construction environment along with fast economy development. But, various problems that must think in problem of safety and quality were appeared. Constructions which build through rapid economy development are getting many social criticisms to problem of crack and water leakage at use process. Is situation that huge repair expense to cure this is engaged. Safety problem of construction is indicated socially through various media mediums again.

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