• Title, Summary, Keyword: Shrinkage

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A Characteristic of Autogenous shrinkage and Dry shrinkage for High Performance Concrete Using Type I and Type IV Cement (1종 및 4종시멘트를 이용한 고성능 콘크리트의 자기수축 및 건조수축 특성)

  • Lee Woong-Jong;Ryu Jae-Sang;Lee Jong-Ryul
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.561-564
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    • 2004
  • In this study, the properties of autogenous shrinkage and dry shrinkage for high performance concrete using Type I and Type IV cement were discussed. According to experimental results, autogenous shrinkage of SN30(the high performance concrete using type I cement) shows values higher than SL30( the high performance concrete using type IV cement). But the dry shrinkage of SN30 is almost the same as SL30. It is observed that the total shrinkage strain of SN30 is higher than that of SL30, because the ratio of autogenous shrinkage of the total shrinkage is relatively large. Therefore, SL30 is more effective to control or minimize the cracking of the high performance concrete, compared with SN30.

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Changes of Camber on Lamination Conditions in alumina/Tungsten Cofiring Multilayer Package (알루미나/텅스텐 동시소성에 의한 다층 팩키지 제조시 적층조건에 따른 camber의 변화)

  • 성재석;구기덕;윤종광;이상진;박정현
    • Journal of the Korean Ceramic Society
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    • v.34 no.6
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    • pp.601-610
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    • 1997
  • In cofiring of multilayered alumina with tungsten, the change of camber with lamination condition was experimented and the effect of sintering shrinkage of alumina and tungsten was investigated. From the exact measurement of sintering shrinkage of tungsten thick film, as lamination pressure increased, the sintering shrinkage of alumina decreased but that of tungsten thick film was not changed. So it was though that the main factor which induced the sintering shrinkage difference between ceramics and metal with lamination condition was the change of sintering shrinkage of ceramics. In case of high lamination pressure, high green sheet density, the cofired specimen showed low camber due to low shrinkage difference between alumina and tungsten and there was a linear relation between camber and shrinkage difference. It was found that this shrinkage difference could change the thickness of tungsten film and the microstructure within via hole during cofiring.

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Analysis of Fabric Shrinkage in Sewing Machine Embroidery (기계자수 원단의 수축에 관한 연구)

  • 강창희;안춘순
    • Journal of the Korean Society of Clothing and Textiles
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    • v.28 no.8
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    • pp.1057-1064
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    • 2004
  • Silk, polyester, cotton, and wool fabrics were embroidered with varying stitch length of 3mm, 5mm, and 10mm to examine the difference in fabric shrinkage in terms of sewing direction, fabric thickness, cover factor, stitch length, and fiber type. Warp, filling, and bias direction of sewing resulted in no difference in fabric shrinkage. Within the samples with same stitch length, there was less fabric shrinkage in fabrics with higher fabric thickness or higher cover factor. There was larger shrinkage when sewn with longer stitch length. Comparing fabrics with different fiber types but similar fabric thickness, silk and polyester fabrics showed the smallest fabric shrinkage and wool fabrics showed the largest shrinkage. It is shown that similar fabric shrinkage between silk and polyester is due to the similarity in cover factor.

The Effect of Casting Conditions on Shrinkage and Porosity of A356.2 Alloys (A356.2 합금의 수축과 기공에 미치는 주조 조건의 영향)

  • Jeon, Gyu-Tae;Kim, Ki-Young;Kim, Suk-Jun
    • Journal of Korea Foundry Society
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    • v.37 no.6
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    • pp.193-198
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    • 2017
  • In this study, volumes of shrinkage and porosity of A356.2 alloys during casting were analyzed as a function of melt temperature, pouring diameter, mold temperature, and Sr content. The temperature of the melt barely affected the shrinkage and porosity formation. The pouring diameter determined the pouring rate, and it was proportional to the shrinkage, yet no relationships with the density of porosity were observed. When the mold was heated at $400^{\circ}C$, shrinkage and porosity in the alloy increased above the one in the mold without heating. However, the mold without heating experienced interior shrinkage and the porosity was mainly distributed near interior shrinkage. The addition of Sr to the melt resulted in more shrinkage and less porosity.

THE EFFECT OF VISCOSITY, SPECIMEN GEOMETRY AND ADHESION ON THE LINEAR POLYMERIZATION SHRINKAGE MEASUREMENT OF LIGHT CURED COMPOSITES (점도, 시편형태 그리고 접착의 유무가 광중합 복합레진의 선형중합수축의 측정에 미치는 영향)

  • Lee, In-Bog;Son, Ho-Hyun;Kwon, Hyuk-Chun;Um, Chung-Moon;Cho, Byeong-Hoon
    • Restorative Dentistry and Endodontics
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    • v.28 no.6
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    • pp.457-466
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    • 2003
  • The aim of study was to investigate the effect of flow, specimen geometry and adhesion on the measurement of linear polymerization shrinkage of light cured composite resins using linear shrinkage measuring device. Four commercially available composites - an anterior posterior hybrid composite Z100, a posterior packable composite P60 and two flowable composites, Filtek flow and Tetric flow-were studied. The linear polymerization shrinkage of composites was determined using 'bonded disc method' and 'non-bond-ed' free shrinkage method at varying C-factor in the range of 1∼8 by changing specimen geometry. These measured linear shrinkage values were compared with free volumetric shrinkage values. The viscosity and flow of composites were determined and compared by measuring the dropping speed of metal rod under constant load. In non-bonded method, the linear shrinkage approximated one third of true volumetric shrink-age by isotropic contraction. However, in bonded disc method, as the bonded surface increased the linear shrinkage increased up to volumetric shrinkage value by anisotropic contraction. The linear shrinkage value increased with increasing C-factor and approximated true volumetric shrinkage and reached plateau at about C-factor 5∼6. The more flow the composite was, reduced linear shrinkage was measured by compensation radial flow.

A STUDY OF CONTRACTION SHRINKAGE OF COMPOSITE RESINS AND ORMOCERS WITH VARIOUS CURING TIMES (광조사 시간에 따른 복합레진과 Ormocer의 중합수축에 관한 연구)

  • Chung, Yeon-Chung;Min, Kyung-San;Lee, Hae-Hyoung;Cho, Kyung-Mo;Cho, Yong-Bum
    • Restorative Dentistry and Endodontics
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    • v.28 no.4
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    • pp.326-333
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    • 2003
  • Ormocer has organic-inorganic compound polymers. One of advantages of ormocer is reduced polymerization shrinkage. The purpose of this study was to compare the amount of contraction shrinkage of composite resins and ormocers. Additionally, the time of each material when there is no further change of contraction shrinkage was analysed. Four brands of composite resins (P-60. Surefil, Z-250 and Denfil) and two brands of ormocers (Definite and Admira) were used. 20 seconds, 40 seconds and 60 seconds of curing times were given. Contraction shrinkage of them were measured using a linometer for 80 seconds. The effect of material and curing time to contraction shrinkage at the time of 80 seconds was analysed by two-way ANOVA. The effect of time to contraction shrinkage was analysed by one-way ANOVA and the time when there was no further change of the contraction shrinkage was analysed. The results are as follows: 1. P-60, Definite, Z-250 and Denfil had no further change of contraction shrinkage from the time of 20 seconds, and Surefil and Admira had no further change of contraction shrinkage from the time of 10 seconds. 2. Statistical analysis revealed volumetric shrinkage varied among material (p<0,05). No significant difference of contraction shrinkage among different curing times was found, and there was no effect of interaction between materials and curing times to contraction shrinkage. 3. Definite and Admira showed the statistically same contraction shrinkage with those of Z-250 and P-60. which is higher than that of Surefil and lower than that of Denfil (p<0.05).

Shrinkage Stress Analysis of Concrete Slab with Shrinkage Strip in Multi-Story Building (수축대를 사용한 고층건물 콘크리트 슬래브의 건조수축응력 해석)

  • 김한수;조석희
    • Journal of the Korea Concrete Institute
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    • v.14 no.5
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    • pp.726-733
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    • 2002
  • Shrinkage strip or separation strip is a temporary joint that is left open for a certain time during construction to allow a significant part of the shrinkage to take place without inducing stress. A shrinkage stress analysis method of shrinkage strip in concrete slab of multi-story building considering the relaxation effect of creep and construction sequence is proposed. The analysis results of 10-story example building show that the effect of shrinkage strip can be analyzed easily by the proposed method. And shrinkage strip installed in a particular floor makes the stress of that floor reduced and the stress of the other floors increased a little. The rate and amount of stress reduced with closing time mainly depends on the development of shrinkage with time of concrete model used. The amount of stress reduced is determined by the amount of shrinkage strain developed before the closing of shrinkage strip.

Shrinkage Properties of High Performance Concrete Used Expansive Additive and Shrinkage Reducing Agent (팽창재와 수축저감제를 사용한 고성능 콘크리트의 수축 특성)

  • Koh, Kyung Taek;Park, Jung Jun;Ryu, Gum Sung;Kang, Su Tae
    • Journal of The Korean Society of Civil Engineers
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    • v.26 no.4A
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    • pp.787-794
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    • 2006
  • Generally, high performance concrete has characteristics such as low water-cementitious material ratio, lots of unit binder powder, thus the heat of hydration, autogenous shrinkage are tend to be increased. This study is to investigated the effect of the expansive additive and shrinkage reducing agent on the shrinkage properties of high performance concrete as a study to develop the reduction technology of the concrete shrinkage. Test results showed that the expansive additive and shrinkage reducing agent were effective the reduction of shrinkage of high performance concrete. Especially, the using method in combination with expansive additive and shrinkage reducing agent was more effective than the separately using method of that. Also, it analyzed that the combination of expansive additive of 5% and shrinkage reducing agent of 1% was the most suitable mixture, considering to the fluidity, strength and shrinkage properties.

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Performance Improvement of High Performance Shrinkage Reducing Agent using Early Strength Improving Agent (조기강도 개선제를 활용한 고성능 수축저감제의 성능 개선)

  • Park, Jong-Pil;Jung, Yong-Wook
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.4
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    • pp.296-302
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    • 2016
  • Studies aimed at reducing the occurrence of cracks by the shrinkage of concrete are in demand because the repair and reinforcement for cracks caused by declining concrete durability costs the user to maintain the concrete structure. In particular, in underground power facilities for power transmission, the cost is a heavy burden to repair and reinforce. For this reason, underground power facilities demanded effective methods for crack reduction at the engineering design step. This study, as a part of the development of shrinkage reducing agent for low shrinkage concrete on underground power facilities, investigated TEA to complement the shrinkage reducing agent to improve the early strength of concrete. In the case of TEA 3% as a shrinkage reducing agent, the early strength was improved significantly, and the shrinkage reducing effect was excellent. In addition, TEA 3.0 % and the shrinkage reducing agent 2.0 % showed excellent shrinkage property and compressive strength. On the other hand, more study of shrinkage reducing materials, including performance reviews on the shrinkage reducing materials with variable factors and type of materials, will be needed to generalize these results.

A Study on Modelling for Prediction of Concrete Drying Shrinkage according to Properties of Aggregate (잔골재 특성에 따른 콘크리트 건조수축 모델링에 관한 연구)

  • Park Do-Kyong;Yang Keek-Young
    • Journal of the Korea Institute of Building Construction
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    • v.6 no.1
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    • pp.73-77
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    • 2006
  • Drying Shrinkage has much complexity as it has relations with both internal elements of concrete and external factors. Therefore, experiments on Concrete Drying Shrinkage are carried out in this study under simplified circumstances applying temperature & Humidity test chamber which enables constant temperature and humidify. Comparative analyses have been made respectively according to the consequences aiming at modelling for prediction of Concrete Drying Shrinkage and making out measures to reduce it. As a result Strain Rate of Drying Shrinkage of concrete was measured to increase by average $10{\times}10^{-5}$ in proportion to additional 4% increase in fine aggregate ratio, when water/cement ratio constant. Strain Rate of Drying Shrinkage in pit sand concrete increased 20% higher than measured when in river sand under the condition of 90-day material age. 6. Strain Rate of Drying Shrinkage in sea sand concrete increased $10%{\sim}15%$ higher than measured when in river sand. The results of prediction of Rate of Drying Shrinkage by Response Surface Analysis are as fellows. The coefficient of correlation of Drying Shrinkage in concrete was over 90%.