• Title/Summary/Keyword: total shrinkage

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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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    • 2000.10a
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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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Differential Drying Shrinkage and Autogenous Shrinkage of Concrete at Early Ages (초기재령 콘크리트의 부등건조수축과 자기수축에 관한 연구)

  • 김진근;이칠성
    • Proceedings of the Korea Concrete Institute Conference
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    • 1998.04a
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    • pp.309-314
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    • 1998
  • The moisture diffusion and self-desiccation cause the differential drying shrinkage and autogenous shrinkage at early ages, respecitvely. Thus total shrinkage strain includes the differential drying shrinkage and self-desiccation shrinkage. Thus in this study the shrinkage strain was measured at various positions in the exposed concrete and in the sealed concrete the self-desiccation shrinkage was measured. In low-strength concrete, the differential drying shrinkage increases very rapidly, but self-desiccation shrinkage is very small. But high-strength concrete shows the reverse result. And the analytical results for differential drying shrinkage were in good agreement with the test results.

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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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    • 2004.11a
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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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The Properties of Stress Induced by Autogenous Shrinkage and Dry Shrinkage for High Strength Concrete Using Type I and Type IV Cement (보통 및 저열시멘트를 이용한 고강도 콘크리트의 자기수축응력 및 건조수축응력 특성)

  • Lee Woong-Jong;Um Tae-Sun;Lee Jong-Ryul
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.05b
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    • pp.17-20
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    • 2005
  • In this study, the properties of autogenous shrinkage stress and dry shrinkage stress for high strength concrete using Type I and Type IV cement were discussed. According to experimental results, autogenous shrinkage stress of SN30(the high strength concrete using type I cement) shows values higher than SL30(the high strength concrete using type IVcement). It is observed that the total shrinkage stress of SN30 is higher than that of SL30, because the ratio of autogenous shrinkage stress of the total shrinkage stress is relatively large. Therefore, SL30 is more effective to control or minimize the cracking of the high strength concrete, compared with SN30.

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Evaluating shrinkage and mechanical performances of polypropylene hybrid fibers reinforced mortar

  • Bendjillali, Khadra;Bendjilali, Fatiha;Krobba, Benharzallah
    • Advances in materials Research
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    • v.11 no.3
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    • pp.211-224
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    • 2022
  • The shrinkage and the mechanical properties of polypropylene hybrid fiber reinforced mortar PHFRM were investigated in this study. Mortars were prepared with limestone crushing sand, Portland cement and polypropylene hybrid fibers PHF. Two types of virgin fibers, having the same length (30 mm) were used for reinforcing test mortars, fibers in diameter of 0.45 mm, used by PLAST BROS factory of Bordj Bou Arreridj (Algeria) for the fabrication of brooms (for household cleaning) and fibers in diameter of 0.25 mm, available on the market, having multiple applications. In this investigation, it was aimed to study the total and autogenous shrinkage, the flexural and compressive strength of mortars based on hybrid fibers. As a result, PHF have negatively affected the mortar workability. However, shrinkage risk was reduced and coarser fibers (PF45) were most effective for reducing shrinkage risk. The mechanical performances and the ductility of PHFRM were also enhanced.

Prediction of Curl Distortion using Classical Lamination Theory in Stereolithography (SL 광조형 공정에서 고전적층이론을 적용한 곡률 변형 예측)

  • Kim, Gi-Dae;Lee, Jae-Kon
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.11 s.176
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    • pp.210-217
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    • 2005
  • A curl distortion induced by shrinkage during stereolithography polymerization process is analyzed with the classical lamination theory. Test parts of different layer thickness and part thickness are manufactured and their deformations are measured with CMM. Curl distortion is generated by the differential shrinkage of the layers, where the total shrinkage includes the shrinkages due to solidification and the change of temperature. It is shown that the curl distortion increases exponentially with decreasing the total thickness of the part, whose smaller layer thickness induces larger curl distortion. It is verified that only a part of the total shrinkage plays a role in generating the curl distortion.

Study on Movement of Wood (목재(木材)의 치수변동(変動)에 관(關)한 연구(硏究))

  • Jung, Hee-Suk;Lee, Phil-Woo;Lee, Nam-Ho
    • Journal of the Korean Wood Science and Technology
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    • v.14 no.2
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    • pp.36-42
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    • 1986
  • Both the control and heated specimen of oak, hornbean, alder, poplar, red pine and pitch pine among domestic commercial species and taun imported were used for radial and tangential shrinkage and movement that occurred on changing the relative humidity of the atmosphere from 90 percent to 60 percent at $25^{\circ}C$. The results of this study were as follows. 1. The radial and tangential shrinkage of the control and heated hornbean and oak wood, except alder, of high specific gravity showed greater than species with low specific gravity. The ratio of tangential to radial shrinkage was 1.46 for taun to 2.70 for alder. Green volume specific gravity of the heated and soaked specimen of all species except poplar decreased 1.5 to 3.1 percent. Shrinkage of the heated specimen increased more than that of the control specimen, and antishrink efficiency of all timbers except alder had negative value. Shrinkage from green to air dry of treated specimens increased more than case of total shrinkage, and radial shrinkage of those specimen increased greater than tangential shrinkage. 3. The movement of the heating specimen for 120 hours decreased than those of the control and the heating specimen for 240 hours. The movement of heating oak, poplar, red pine and pitch pine (or 240 hours increased rather than those of the control specimen.

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The Study on Relationship Between Thermal Stress Properties and Thermal Shrinkage of PET Filament Yarns (PET 필라멘트사의 열응력특성과 열수축율과의 상관성연구)

  • 김영진;김승진;김태훈;김경렬;박인동
    • Textile Coloration and Finishing
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    • v.10 no.2
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    • pp.45-54
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    • 1998
  • This study surveys relation between thermal shrinkage and thermal stress properties after process simulation of heat treatment with various PET filament yarns. For this purpose, 12 kinds of regular yarns and POY, 6 kinds of DTY and 5 kinds of composite yarns were experimented for investigating step thermal shrinkage, total thermal shrinkage and total thermal stress and maximum thermal stress temperature. Thermal stress and shrinkage of the various specimens treated with wet and dry heats were analysed and discussed with the conditions of heat treatment. finally, relationship between thermal stress and shrinkage of the various PET filaments such as regular yarns, POY, DTY and composite yarns were investigated with the PET filament characteristics.

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Influence of Curing Conditions on Volumetric Changes in Concrete (양생 조건이 콘크리트의 체적 변화에 미치는 영향)

  • Lee, Kwang-Myong;SunWoo, Joo-Yeun;Lee, Hoi-Keun;Khayat, Kamal H.
    • Journal of the Korea Concrete Institute
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    • v.18 no.3 s.93
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    • pp.331-338
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    • 2006
  • This paper presents the experimental results on volumetric changes in ordinary portland cement concrete made with various water-to-cement ratios(W/C's) ranging from 0.32 to 0.50 and cured in low different conditions. Curing regimes employed in this work were designed to exhibit autogenous and drying shrinkage as well as swelling of concrete. The concrete avoided any moist evaporation(Regime f showed only autogenous shrinkage and the lower the W/C, the feater the autogenous shrinkage. The concrete exposed to air drying conditions at $20{\pm}1^{\circ}C$ and $60{\pm}3%$ RH after 6-day water curing at $20{\pm}1^{\circ}C$(Regime II) swelled and then started to shrink. The maximum swelling value of concrete developed in water curing was between 15 and $40{\pm}10^{-6}$, and the greatest total shrinkage(autogenous+drying shrinkage) was obtained for the mixture made with W/C of 0.32. The concrete let to air drying conditions(Regime III) showed greater total shrinkage compared to the concrete cured in Regime II. The concrete exposed to air drying condition after 6-day sealed curing(Regime IV) exhibited slightly smaller total shrinkage than that of the concrete cured in Regime III. Net drying shrinkage that can be derived from the results of Regime I, III, and IV increased as the W/C increased despite of similar total shrinkage. This result indicated that drying shrinkage governs total shrinkage of high-W/C concretes. In other words, a portion of autogenous shrinkage in total shrinkage increased in low-W/C concretes. Therefore, it should be controlled in terms of cracking potential. Finally, total shrinkage of high-strength and high-performance concrete made with low W/C can be effectively reduced by appropriate early moisture curing.

Autogenous Shrinkage Stress in Reinforced Concrete Beams (철근콘크리트 보에서 자기수축응력)

  • 최익창;김대웅
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.05a
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    • pp.101-106
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    • 2003
  • This study is to capture autogenous shrinkage in reinforced concrete. The experiment was carried out on total 13 beams. The experiment parameters are a method of curing and reinforcement ratio. Autogenous shrinkage in reinforced concrete beam was experimentally measured. Also, the distribution of autogenous shrinkage and self stress on cross section in reinforced concrete beams were calculated. The experimental results showed that autogenous shrinkage of high strength concrete were significantly higher than that of nomal strength concrete.

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