• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1009-1012
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• 2008

The fiber dispersion performance in fiber-reinforced cementitious composites is a crucial factor with respect to achieving desired mechanical performance. However, evaluation of the fiber dispersion performance in the composite PVA-ECC(Polyvinyl alcohol-Engineered Cementitious Composite) is extremely challenging because of the low contrast of PVA fibers with the cement-based matrix. In the present work, an enhanced fiber detection technique is developed and demonstrated. Using a fluorescence technique on the PVA-ECC, PVA fibers are observed as green dots in the cross-section of the composite. After capturing the fluorescence image with a Charged Couple Device(CCD) camera through a microscope. The fibers are more accurately detected by employing a series of process based on a categorization, watershed segmentation, and morphological reconstruction.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.705-712
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• 2009

HPFRCCs (high-performance fiber reinforced cementitious composites), which is relatively more ductile and has the characteristic of high toughness with high fiber volume fractions, can be used in structures subjected to extreme loads and exposed to durability problems. In the case of PVA (polyvinyl alcohol) fiber, it is noted by former studies that around 2% fiber volume fractions contributes to the most effective performance at HPFRCCs. In this study, flexural tests were carried out to evaluate the flexural behavior of HPFRCCs and to optimize mix proportions. Two sets of hybrid fiber reinforced high performance specimens with total fiber volume fraction of 2 % were tested: the first set prepared by addition of short and long PVA fibers at different combination of fiber volume fractions, and the second set by addition of steel. In addition, in order to assess the performances of the HPFRCCs against to high strain rates, drop weight tests were conducted. Lastly, the sprayed FRP was applied on the bottom surface of specimens to compare their impact responses with non-reinforcing specimens. The experimental results showed that the specimen prepared with 1.6% short fibers (REC 15) and 0.4% long fiber (RF4000) outperformed the other specimens under flexure, and impact loading.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.513-522
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• 2008

The fiber dispersion performance in fiber-reinforced cementitious composites is a crucial factor with respect to achieving desired mechanical performance. However, evaluation of the fiber dispersion performance in the composite PVA-ECC (Polyvinyl alcohol-Engineered Cementitious Composite) is extremely challenging because of the low contrast of PVA fibers with the cement-based matrix. In the present work, an enhanced fiber detection technique is developed and demonstrated. Using a fluorescence technique on the PVA-ECC, PVA fibers are observed as green dots in the cross-section of the composite. After capturing the fluorescence image with a Charged Couple Device (CCD) camera through a microscope. The fibers are more accurately detected by employing a series of process based on a categorization, watershed segmentation, and morphological reconstruction.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.305-308
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• 2006

This paper is to investigate the strength, impact endurance and shrinkage of wet spraying type fiber composite mortar for repair material depending on fiber type and product kinds. Fiber composite mortar containing PVA fiber had the highest strength compared to that using any other fiber. Especially, The use of PVA fiber results in a remarkable enhancement in impact strength and an improved volumetric stability. Accordingly, it is confirmed that fiber composite mortar containing PVA fiber has remarkable performance as repair material of damaged section of concrete.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.4
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• pp.29-35
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• 2013

The objective of the current study is to evaluate the effects depending on the types of reinforcing fibers being influential in view of mechanical properties and impact resistance of hybrid fiber reinforced concrete (HFRC) for applications to precast concrete structure. Hybrid fibers applied therefor were three types such as PP/MSF (polypropylene fiber+macro synthetic fiber), PVA/MAF (polyvinyl alcohol fiber+MSF) and JUTE/MSF (natural jute fiber+MSF), where the volume fraction of PP, PVA and natural jute was applied with 0.2 %, respectively, while based on 0.05 % volume fraction of MSF. The HFRC was tested for slump, compressive strength, flexural strength and impact resistance. The test result demonstrated that mixture of such hybrid fibers improve compressive strength, flexural strength and impact resistance of concrete. Moreover, it was found that HFRCs to which hydrophilic fibers, i.e. PVA/MSF and JUTE/MSF, were mixed show more improved features that HFRC to which non-hydrophilic fiber, i.e. PP/MSF was mixed. Meanwhile, the finding that PVA/MSF HFRC exhibited better performance than JUTE/MSF HFRC was attributed from the former having higher aspect ratio than that of the latter.

• Proceedings of the Korean Fiber Society Conference
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• 2001.10a
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• pp.187-190
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• 2001

The poly(vinyl alcohol) (PVA) fiber is recognized as the best candidate because of its good machanical properties together with excellent resistance to alkalis[1-5]. PVA cannot be prepared by the direct polymerization due to tautomerism of vinyl alcohol monomer. Thus PVA is obtained by the saponification of poly(vinyl ester) like poly(vinyl acetate) (PVAc). (omitted)

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.29-32
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• 2005

An experimental investigation on the strength and behavior of High Performance Fiber Reinforced Cement Composite(HPFRCC) column with Polyvinyl alcohol(PVA) fibers under axial load have been carried out. The columns were subjected to monotonic axial compression until failure. The variables in this study are the combination ratio of PVA, and the volumetric ratio of transverse reinforcement. Test results showed that the fibers, when used in PVA2.0, could result in superior composite performance compared to their individual fiber reinforced cement composites.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.389-392
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• 2006

In this study, I examined hardening and non-hardening of the DFRCC (Ductile Fiber Reinforced Cementitious Composites) according to sand-aggregate ratio and the diameter of PVA fiber to develope PVA fiber reinforced concrete with the feature of DFRCC. As a result of this study, the fresh properties of DFRC is similar regardless of sand-aggregate ratio. The bending stress of DFRC also increased as the sand-aggregate ratio increased. And the bending stress-displacement was the most stable when the PVA $100{\mu}m$ was used regardless of sand-aggregate ratio.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.33-36
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• 2002

폴리비닐알코올 (poly(vinyl alcohol), PVA)은 의류 및 산업용 섬유, 막, 약물전달, 암세포 괴사용 색전제등에 널리 사용되고 있다[1,2]. 이런 PVA와 같은 비닐계 고분자는 분자량 이외에도 입체규칙성에 따라 그 물리적 성질이 변화하는데 그 입체규칙성에 따라 혼성배열, 동일배열 및 교대배열 고분자로 분류할 수 있다. PVA는 일반적으로 55% 이상의 교대배열 다이애드기 함량을 가질 때 교대배열 PVA라고 불린다. (중략)

• Proceedings of the Korean Fiber Society Conference
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• 2003.10b
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• pp.165-166
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• 2003

완전히 가수분해 된 폴리비닐알콜(PVA)은 에멜전 안정화와 계면활성이 약하다. $^{1)}$ 하지만 hydrophobically modified PVA는 높은 계면활성을 가지고 있을뿐더러 수용액에서 micelle을 형성할 수 있고 게다가 그의 수용액은 높은 viscosity, shear thinning, thixotropic, less salt sensitive 성질을 가지고 있어 enhanced oil recovery operations, drag reduction, flocculation, super absorbency, latex paints, hydraulic fluids, surface coatings등에 사용될 수 있다. $^{2.3)}$ (중략)