• Title, Summary, Keyword: Shrinkage

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Simulation of concrete shrinkage taking into account aggregate restraint

  • Tangtermsirikul, Somnuk;Nimityongskul, Pichai
    • Structural Engineering and Mechanics
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    • v.5 no.1
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    • pp.105-113
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    • 1997
  • This paper proposes a model for simulating concrete shrinkage taking into account aggregate restraint. In the model, concrete is regarded as a two-phase material based on shrinkage property. One is paste phase which undergoes shrinkage. Another is aggregate phase which is much more volumetrically stable. In the concrete, the aggregate phase is considered to restrain the paste shrinkage by particle interaction. Strain compatibility was derived under the assumption that there is no relative macroscopic displacement between both phases. Stresses on both phases were derived based on the shrinking stress of the paste phase and the resisting stress of the aggregate phase. Constitutive relation of paste phase was adopted from the study of Yomeyama, K. et al., and that of the aggregate phase was adopted from the author's particle contact density model. The equation for calculating concrete shrinkage considering aggregate restraint was derived from the equilibrium of the two phases. The concrete shrinkage was found to be affected by the free shrinkage of the paste phase, aggregate content and the stiffness of both phases. The model was then verified to be effective for simulating concrete shrinkage by comparing the predicted results with the autogeneous and drying shrinkage test results on mortar and concrete specimens.

Heat Shrinkage Change of PVC Fiber with the Overfeed Ratio of Drawing Process (연신 공정의 overfeed율 변화에 따른 PVC사 열수축률 변화)

  • 박용완;김환철;박병기
    • Textile Science and Engineering
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    • v.38 no.6
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    • pp.279-285
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    • 2001
  • Since a drawn fiber shrinks when treated with heat, fiber is treated with heat after drawing process to prevent heat shrinkage. The objective of this study is to investigate the effects of drawing conditions on the properties of PVC fiber, especially on heat shrinkage. Overfeed was applied to prevent heat shrinkage at the several positions during drawing process. Heat shrinkage increased with draw ratio, and decreased with overfeed ratio. Overfeed was most effective to reduce heat shrinkage when applied between the chamber 2 roller and the take-up roller. The chlorinated PVC(CPVC) content also affected the heat shrinkage, and heat shrinkage decreased with increasing CPVC ratio.

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Influence of Shrinkage Reducing Agent on Drying Shrinkage of Mortar (모르타르의 건조수축에 미치는 수축저감제의 영향)

  • 이승한;정용욱;박정섭
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.563-566
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    • 2000
  • The study is to examine the drying shrinkage reducing method of mortar using organic shrinkage reducing agent. According to the experiment result, when 2% and 4% of organic shrinkage reducing agent were added, 40% and 50% of the shrinkage rate of mortar were obtained. Also, in the cracking test of plate-shape specimen, the usage of shrinkage agent 2% reduced about 60% of the total cracking length compare to total cracking length the usage of portland cement, the usage of shrinkage agent 4% was not happened crack until 90 days. Accordingly, the usage of shrinkage agent show good effect in prevention of crack.

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Shrinkage in Injection molded Part for Operational Conditions and Resins (성형조건과 수지의 종류에 따른 사출 성형품의 성형 수축)

  • 모정혁;김현진;류민영
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.363-370
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    • 2003
  • Shrinkage of injection molded parts is different form operational conditions of injection molding such as injection temperature, injection pressure and mold temperature, and mold design such as gate size. It is also various for different resins which have crystalline structure or not. In this study part shrinkage was investigated for various operational condition and resins; PBT for crystalline polymer, and PC and PMMA for amorphous polymer was used in experiment. Crystalline polymer shows higher part shrinkage by about three times than amorphous polymer. Part shrinkage increased as injection temperature and mold temperature increased and injection pressure decreased. Part shrinkage decreased as gate size increased since the pressure delivery is mush easier for large gate size. Part shrinkage according to the gate location was that the position in the part with close to the gate showed large shrinkage and this phenomenon might be occurred by residual stress.

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Autogenous Shrinkage of Concrete Containing Blast-Furnace Slag (고로 슬래그를 함유한 콘크리트의 자기 수축)

  • 이회근;권기헌;이광명;김규용;손유신
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.417-420
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    • 2003
  • Concrete with low water to binder ratio (W/B) is prone to large autogenous shrinkage. Early age cracking of concrete would be caused by tensile stress induced by large autogenous shrinkage under restrained condition. Therefore, it is necessary to measure autogenous shrinkage to control the early age cracking of concrete. An objective of this study is to investigate the effects of W/B and blast furnace slag (BFS) on autogenous shrinkage of concrete. Autogenous shrinkage of concrete with various W/B ranging from 0.42 to 0.27 and BFS contents of 0, 30 and 50% were measured. Test results show that the autogenous shrinkage of concrete increases as the W/B decreases, and all BFS concretes showed larger autogenous shrinkage than OPC concretes with the same W/B. Moreover, the higher BFS content, the larger autogenous shrinkage.

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A Study of the Shrinkage Reduction in High Performance Concrete according to the Adding Ratio of Anti-Shrinkage Agent (수축저감제 혼입률 변화에 따른 고성능 콘크리트의 수축저감에 관한 연구)

  • 한천구;김호림;문학용;강수태;고경택;김도겸
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.473-476
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    • 2003
  • This study discusses the use of anti-shrinkage agent as the method to reduce autogenous and drying shrinkage. According to results, as for the fundamental properties of high performance concrete, fluidity and strength decrease with an increase of the adding ratio of anti-shrinkage agent, but air content increases. Compared with plain concrete, autogenous and drying shrinkage are reduced by 12~52% and 4~22% respectively upto the adding rario of anti-shrinkage agent of 2.0%. When expansive additive is added by 5.0%, they are also reduced by 38~95% and 15~50% respectively. Therefore, as expansive additive of 5.0% and anti-shrinkage agent of 1.0% are added to high performance concrete of around W/B 30%, it is considered that fluidity and strength are hardly influenced, and in addition, crack by shrinkage can be prevented effectively.

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An Experimental Study on Effect of Water-to-Binder Ratio and Admixture on Autogenous Shrinkage of Ultra High Strength Concrete (W/B와 혼화재 치환율이 초고강도 콘크리트의 자기수축에 미치는 영향에 관한 실험적 연구)

  • Kim, Tae-Hoon;Kim, Ji-Won;Sohn, Yu-Shin;Yoon, Young-Soo
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.13-16
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    • 2006
  • This paper investigates the shrinkage behavior of Ultra High Strength(UHSC) having three water-to-cementitious material ratio, 0.20, 0.16, 0.12. All of mixtures have same design compressive strength. Free shrinkage test for autogenous and drying shrinkage using $100{\times}100{\times}400$ prismatic specimen was conducted. On all mixture, Effects of fly ash and blast-furnace slag on each shrinkage test results were also investigated. The largest portion of autogenous shrinkage was observed in UHSC12 (w/b=0.12) and the measured strain was as high as 80% of the total drying shrinkage strain. The autogenous shrinkage of UHSC decreased as the amount of fly ash increased as demonstrated in the literature. However, the results of the effect of blast-furnace slag on autogenous shrinkage were somewhat different from previous researches.

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Effect of Autogenous Shrinkage on Shrinkage behavior in High Stength Concrete (자기건조수축을 고려한 고강도 콘크리트의 수축변형 특징에 관한 연구)

  • Paek, Nak-Seung;Cha, Soo-Won;Lee, Seong-Cheol
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.429-432
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    • 2006
  • The shrinkage mechanism of high strength concrete is different from that of normal concrete. The shrinkage of normal concrete is subjected to evaporate moisture in concrete, but most shrinkage in high strength concrete is caused by chemical reaction. To analyze shrinkage of concrete exactly, it is necessary to divide drying shrinkage with autogenous shrinkage in terms of degree of hydration, especially in concrete with low W/C ratio. The proposed method can provide a rational basis for prediction of shrinkage in high strength concrete structure.

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The Evaluation of Properties on Autogenous Shrinkage and Dry Shrinkage of High Strength Concrete (고강도 콘크리트의 자기수축 및 건조수축특성 평가)

  • Lee, Woong-Jong;Um, Tae-Sun;Lee, Jong-Ryul;Makoto, Tanimura
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.485-488
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    • 2006
  • The shrinkage properties of the high strength concrete using the cement of Type I, Type III and Type IV was examined, and the following results were obtained. (1) Consideration of the autogenous shrinkage when evaluating appropriately the shrinkage properties of the high strength concrete is indispensable. (2) The autogenous shrinkage prediction expression of JSCE can estimate the properties of autogenous shrinkage of the cement made from korea with in general sufficient accuracy. (3) It is necessary to advance examination which used Korean aggregate about dry shrinkage from now on, and to attain highly accuracy of the autogenous shrinkage prediction expression.

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An Experiment Study on Drying Shrinkage Reduction of Concrete Slab (슬래브 구조물용 콘크리트의 건조수축 저감에 관한 연구)

  • Sohn Yu Shin;Lee Seung Hoon;Park Chan Kyu;Kim Gyu Dong
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.592-595
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    • 2004
  • This Study discusses the properties of drying shrinkage of concrete slab with W/B, water content, fiber and anti-shrinkage agent. According to results, drying shrinkage is reduced with decrease of water content and W/B. Also, compared with plain concrete, drying shrinkage is reduced by using of fiber, anti-shrinkage agent and adding ratio of anti - shrinkage agent. Therefore, in the range of workability if water content and W/B are reduced and using of fiber and anti-shrinkage agent are performed properly, crack by drying shrinkage can be prevented effectively.

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