• Title/Summary/Keyword: 동결융해시험

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Bond Behavior of Recycled Coarse Aggregate Concrete Deteriorated by Freezing and Thawing (동결융해를 받은 순환 굵은골재 콘크리트의 부착성능)

  • Choi, Ki-Sun;Lee, Min-Jung;Yun, Hyun-Do;Kang, Ki-Woong;You, Young-Chan;Kim, Keung-Hwan
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.1097-1100
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    • 2008
  • The purpose of this study to investigate the bond strength of recycled coarse aggregate concrete deteriorated by freezing and thawing. Concrete specimens with recycled coarse aggregate representing lower limit of the quality standard (water absorption : 3.0%, specific gravity : $2.5g.cm^3$) were manufactured and tested. The replacement ratio (0, 30, 60 and 100%) of recycled coarse aggregate and freezing-thawing cycles were considered in this test. From the test results, it was found that the bond strength of normal strength concrete is not affected by the replacement ratio of recycled coarse aggregate under freezing and thawing conditions. Also, the bond strength of the natural and recycled coarse aggregate concrete using AE admixtures was not decreased by frost action.

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Reduction of Shear Strength of Railway Roadbed Materials with Freezing-thawing Cycle (동결융해 반복에 따른 철도노반재료의 전단강도 변화)

  • Choi, Chan yong;Shin, Eun chul;Kang, Hyoun Hoi
    • Journal of the Korean GEO-environmental Society
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    • v.12 no.7
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    • pp.13-21
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    • 2011
  • In seasonal frozen areas with climatic features, which have a temperature difference in the winter and thawing season, changes of mechanical properties of the soil in the zone could be seen between the freezing and thawing surface. In particular, in soil with many fine particles, a softening of the roadbed usually occurs from frost and thawing actions. The lower bearing capacity is a rapidly progressive the softening of roadbed, and occurred a mud-pumping by repeated loading. In this study, the three kind of sandy soil with contents of fine particles were conducted by directly shear box test with the number of cyclic in freeze-thawing and the water content of soil. Subsequently, the relationship between the shear strength and freeze-thaw cycling time was obtained. The shear strength was decreased with the increase of the freeze-thaw cycling time. A shear stress deterioration of the soil with power function modal is proposal.

Strength Properties of Polymer-Modified Repair Mortars According to Curing Conditions and Repair Methods (양생조건 및 보수방법에 따른 폴리머시멘트모르타르의 강도 성상)

  • Kim, Wan-Ki;Jo, Young-Kug
    • Journal of the Korea Concrete Institute
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    • v.19 no.4
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    • pp.457-465
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    • 2007
  • In this paper, polymer-modified repair materials using polymer dispersions with six repair methods are prepared with various polymer-cement ratios, and tested for compressive and flexural strengths through each curing condition such as dry cure, water cure, and freezing and thawing cyclic action. And, the adhesive interface between the polymer-modified mortar and mortar substrate is observed by a scanning electron microscope. From the test results, the compressive and flexural strengths of cement mortar repaired by polymer-modified mortar are improved with a rise in the polymer-cement ratio regardless of the type of polymer and curing conditions. Such an improvement in the strengths of polymer-modified repair materials to ordinary cement mortar is explained by the high adhesion of polymer-modified mortar. Strength reduction of polymer-modified repair materials after freezing and thawing cyclic actions is recognized, but it is lower than that of unmodified mortar. Especially, cement mortar repaired by polymer-modified mortar with a St/BA emulsion has good strength properties compared with those of SBR latex and PA emulsion. Accordingly, it is judged that polymer-modified mortars with a St/BA emulsion are possible to use as repair materials to ordinary cement mortar and concrete.

An Performance Evaluation of the Post-installed Anchor System According to the Freezing and Thawing of Concrete and the Corrosion of Anchor (콘크리트의 동결융해와 앵커의 부식에 따른 후 설치 앵커시스템의 성능평가)

  • Kwon, Min-Ho;Kim, Jin-Sup;Jung, Woo-Young;Kwon, Sang-Won
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.5
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    • pp.31-39
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    • 2013
  • In this study, performance of the post-installed anchor system was evaluated with reduced strength of concrete and anchor. One of the post-installed anchors was selected to performance evaluation. Concrete strength was reduced by freeze-thawing test, and the post-installed anchor strength was reduced by corrosion test. The post-installed Anchor was installed in concrete of freezing and thawing and original concrete, and corroded anchor was installed in original concrete only. Anchor diameter and installation depth of the anchor were the variable for each specimen. Performance of post-installed anchor system of each specimen was evaluated by pullout test. Anchor diameter and installation depth of anchor, it may affect the performance of the post-installed anchor system from the experimental test results. Fracture mode of each post-installed anchor system had occurred differently depending on the durability of concrete and anchor. The anchor pullout strength from the experimental test results was used in order to compare with the results of CCD (Concrete Capacity Design) method, and CCD equation was modified. Modified equation was able to predict the anchor pullout strength of post-installed anchor system in Original concrete and freezing and thawing of concrete.

The Physical Properties of Polymer Concrete for Ultra Thin Bridge Deck Pavement (초박층 교면포장용 폴리머 콘크리트의 물리적 특성)

  • Kim, Hyeon Jun;Son, Yeong Hyo;Han, Bum Jin;Jung, Ji Eun;Park, Sun Kyu
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.3
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    • pp.74-81
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    • 2013
  • This research was performed to identify physical properties of polysulfide epoxy polymer concrete for ultra-thin bridge deck pavement, and improve domestic applicability. With the optimum mix ratio determined from mixing experiments of polymer concretes, compressive, flexural, and bond strength were tested to identify its strength properties along with the freezing-thawing resistance test to evaluate its durability in harsh environments. As a result, the tested polymer concretes showed excellent performance in strength and deflection characteristic and all tested strength satisfied the criteria of American Concrete Institute. Moreover, it had better performance under variable temperatures comparing to other existing pavement materials. By the results of freezing-thawing resistance test and strength measurement for specimens underwent the freezing-thawing process, it can be judged that there is no such problem to the concrete's durability. In conclusion, the newly developed polymer concrete in this research has appropriate properties for use in ultra-thin pavement on bridge deck, and moreover it has superior applicability in comparison with former materials due to its improved temperature sensitivity.

An Experimental Study on the Freeze-Thaw Resistance of Concrete Incorporating Waste Foundry Sand (폐주물사를 혼입한 콘크리트의 동결-융해 저항성에 관한 실험적 연구)

  • 윤경구;이주형;홍창우;박제선
    • Magazine of the Korea Concrete Institute
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    • v.10 no.4
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    • pp.153-161
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    • 1998
  • Concrete structures has been deteriorated by and freezing the thawing due to temperature gap. This study was conducted to evaluate durability of concrete which are increasingly demanded recently. Therefore the research of durability must be executed for application of waste foundry sand concrete real structures. Concrete durability properties incorporating waste foundry sand was performed with the variable of W/C ratio. Sand/Waste foundry sand ratio and Air entrainment-Non air entrainment. Cylinder specimens were made and subjected to freezing and thawing cycle at -18$^{\circ}C$ and 4$^{\circ}C$. Dynamic modulus of elasticity were evaluated as F/T cycle increase. The results show that strength of concrete is increased the W/C ratio decrease, the Sand/Waste foundry sand ratio increases when the concrete contains AE agent and decreasing W/C ratio and AE concrete makes improved resistance of freezing and thawing improved. Especially, resistance of freezing and thawing is improved by Fine aggregate/Waste foundry sand ratio which is 50%, 25%, 0% in a row. Therefore it is turn out the waste foundry sand could be applied to concrete from the experiment.

Application of One-Sided Stress Wave Velocity Measurement Technique to Evaluate Freeze-Thaw Damage in Concrete (콘크리트 동결-융해 손상의 비파죄 평가를 위한 One-Sided 응력파 속도 측정기법의 적용에 관한 연구)

  • Lee, Joon-Hyun;Park, Won-Su
    • Journal of the Korean Society for Nondestructive Testing
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    • v.20 no.4
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    • pp.269-275
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    • 2000
  • It is well recognized that damage resulting from freeze-thaw cycles is a serious problem causing deterioration and degradation of concrete. In general, freeze-thaw cycles change the microstructure of the concrete ultimately leading to internal stresses and cracking. In this study, a new method for one-sided stress wave velocity measurement has been applied to evaluate freeze-thaw damage in concrete by monitoring the velocity change of longitudinal and surface waves. The freeze-thaw damage was induced in a $400{\times}350{\times}100mm$ concrete specimen in accordance with ASTM C666 using s commercial testing apparatus. A cycle consisted of a variation of the temperature from -14 to 4 degrees Celsius. A cycle takes 4-5 hours with approximately equal times devoted to freezing-thawing. Measurement of longitudinal and surface wave velocities based on one-sided stress wave velocity measurement technique was made every 5 freeze-thaw cycle. The variation of longitudinal and surface wave velocities due to increasing freeze-thaw damage is demonstrated and compared to determine which one is more effective to monitor freeze-thaw cyclic damage progress. The variation in longitudinal wave velocity measured by one-sided technique is also compared with that measured by the conventional through transmission technique.

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Durability Characteristics of High Performance Shotcrete for Permanent Support of Large Size Underground Space (대형 지하공간의 영구지보재로서 고성능 숏크리트의 내구 특성)

  • Won, Jong-Pil;Kim, Hwang-Hee;Jang, Chang-Il;Lee, Sang-Woo
    • Journal of the Korea Concrete Institute
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    • v.19 no.6
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    • pp.701-706
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    • 2007
  • This study evaluated the durability of high-performance shotcrete mixed in the proper proportions using alkali-free and cement mineral accelerators as a permanent support that maintains its strength for the long term. Durability tests were performed the chloride permeability, repeated freezing and thawing, accelerated carbonation, and the effects of salt environments. Test results showed that all the shotcrete mixes included silica fume had low permeability. In addition, after 300 freeze/thaw cycles, the shotcrete mix had excellent freeze/thaw resistance more than the 85% relative dynamic modulus of elasticity. The accelerated carbonation test results were no effect of accelerator type but, the depth of carbonation was greater in the shotcrete mix containing silica fume. No damage was seen in a salt environments. Therefore, the high performance shotcrete mix proportions used in this study showed excellent durability.

Evaluation of the Bonding Behavior of the Rehabilitation Method Applying Carbon Fiber Subjected to the Variation of Environmental Condition (탄소섬유 접착 보강공법의 환경변화에 따른 부착특성 평가)

  • Han, Cheon Goo;Byun, Hang Yong;Park, Yong Kyu
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.2
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    • pp.67-74
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    • 2008
  • This paper provides the test results of bonding behavior of the interface between concrete substrate and carbon fiber in the rehabilitation method applying carbon fiber with epoxy based resin adhesive. The difference in each components was gradually increased subjected to the repetition of temperature variation, regardless of the strength of the substrate concrete, while the ultrasonic interface between each component occurred. An increase in difference of the temperature resulted in a decrease in bond strength of each component. Associated failure mode was shown to be interfacial failure and substrate concrete failure. No remarkable changes were found in the deformation and ultrasonic velocity of each component until the four cycles of the dry and moisture test. Hence, the moisture condition may not affect the bonding behavior of each component. After the repetition of dry and moisture test, corresponding bond strength was reduced to 40% of that before test. For the effect of freeze and thaw test, the cycle of freeze and thaw within 4 cycles resulted in debonding of each component.

Effect of Air Void System of High Strength Concrete on Freezing and Thawing Resistance (고강도콘크리트의 동결융해저항에 미치는 기포조직의 영향)

  • 김생빈
    • Magazine of the Korea Concrete Institute
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    • v.4 no.1
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    • pp.89-96
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    • 1992
  • It is generally known that the frost-resistance of concrete is much affected by the air content in concrete and by the air void system or air distribution. And also the frost-resistance is believed to vary with the stre¬ngth of concrete. This article is prepared to describe, based on experiment, the effect of the air content and the air void system, particularly the effect of the spacing factor, on the freeze-thaw resistance of the high strength conc¬rete. For this purpose, I first worked on Non-AE concrete to make its compressive strength set about 400 to 500 kg/em'. However, the freeze-thaw test on the Non-AE concrete resulted in low durability factor, I.e., 10-2~0%. Thus to enhance the durability, another supplementary step was needed. I used AE admixture. which enhanced durability by changing the air content from 2% to 12%. The frost-thaw test was then performed 500 cycles on the 20 kind of concrete mixtures which differ in unit cement content and in water-cement ratio. Keywords : frost -resistance, air content, air void system, air distribution, spacing factor, freeze-thaw test, dur ability factor. capillary cavity, Linear Traverse Method.