• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.349-354
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• 1999

Specialty cellulose fibers processed for the reinforcement of concrete offer relatively high levels of elastic modulus and bond strength. The hydrophilic surfaces of specialty cellulose fibers facilitate their dispersion and bonding in concrete. Specialty cellulose fibers have small effective diameters which are comparable to the cement particle size, and thus promote close packing and development of dense bulk and interface microstructure in the matrix. The relatively high surface area and the close spacing of specialty cellulose fibers when combined with their desirable mechanical characteristic make them quite effective in the suppression and stabilization of microcracks in the concrete matrix. The properties of fresh mixed specialty cellulose fiber reinforced concrete and the contribution of specialty cellulose fiber to the restrained shrinkage crack reduction potential of cement composites at early age and theirs evaluation are presented in this paper. Results indicated that specialty cellulose fiber reinforcement showed an ability to reduce the total area significantly (as compared to plain concrete and polypropylene fiber reinforced concrete.

• Advances in concrete construction
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• 제8권4호
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• pp.311-320
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• 2019

In this study, the effect of cellulose nanocrystals (CNCs) on the fire resistance properties of fiber-reinforced cement composites was investigated. The main variables were CNCs content (0.4, 0.8 and 1.2vol.% compared with cement), steel fiber ratio, and exposure temperature (100, 200, 400, 600 and 800℃). The fire resistance properties, i.e., residual compressive strength, flexural strength, and porosity, were evaluated in relation with the exposure temperature of the specimens. The CNCs suspensions were prepared to composited dispersion method of magnetic stirring and ultra-sonication. CNCs are effective for increasing the compressive strength at high temperatures but CNCs do not seem to have a significant effect on flexural reinforcement. Porosity test result showed CNCs reduce the non-hydration area inside the cement and promote hydration.

• KCI Concrete Journal
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• 제14권1호
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• pp.30-35
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• 2002

The fractal geometry is a non-Euclidean geometry which describes the naturally irregular or fragmented shapes, so that it can be applied to fracture behavior of materials to investigate the fracture process. Fractal curves have a characteristic that represents a self-similarity as an invariant based on the fractal dimension. This fractal geometry was applied to the crack growth of cementitious composites in order to correlate the fracture behavior to microstructures of cementitious composites. The purpose of this study was to find relationships between fractal dimensions and fracture energy. Fracture test was carried out in order to investigate the fracture behavior of plain and fiber reinforced cement composites. The load-CMOD curve and fracture energy of the beams were observed under the three point loading system. The crack profiles were obtained by the image processing system. Box counting method was used to determine the fractal dimension, D$_{f}$. It was known that the linear correlation exists between fractal dimension and fracture energy of the cement composites. The implications of the fractal nature for the crack growth behavior on the fracture energy, G$_{f}$ is apparent.ent.

• Fibers and Polymers
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• 제7권3호
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• pp.286-294
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• 2006

This study has examined the flexural properties of natural and chemically modified coir fiber reinforced cementitious composites (CFRCC). Coir fibers of two different average lengths were used, and the longer coir fibers were also treated with a 1% NaOH solution for comparison. The fibers were combined with cementitious materials and chemical agents (dispersant, defoamer or wetting agent) to form CFRCC. The flexural properties of the composites, including elastic stress, flexural strength, toughness and toughness index, were measured. The effects of fiber treatments, addition of chemical agents and accelerated ageing of composites on the composites' flexural properties were examined. The results showed that the CFRCC samples were 5-12 % lighter than the conventional mortar, and that the addition of coir fibers improved the flexural strength of the CFRCC materials. Toughness and toughness index, which were associated with the work of fracture, were increased more than ten times. For the alkalized long coir fiber composites, a higher immediate and long-term toughness index was achieved. SEM microstructure images revealed improved physicochemical bonding in the treated CFRCC.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 추계 학술논문 발표대회
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• pp.37-38
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• 2016

In this study, it evaluate the coarse aggregate mixed effect to impact resistance performance of the fiber reinforced cement-based material. The type of fiber is Hooked-ended steel fiber, and mixed 1vol.% in concrete and cement composites. The impact experiment was conducted by using a spherical shape projectile diameter of 25mm to 170m/s speed and Impact resistance performance was evaluated by measuring the fracture grade, fracture diameter and depth.

• Computers and Concrete
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• 제16권4호
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• pp.545-568
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• 2015

High Performance Fiber Reinforced Cementitious Composites which are called HPFRCC, include cement matrices with strain hardening response under tension loading. In these composites, the cement mortar with fine aggregates, is reinforced by continuous or random distributed fibers and could be used for various applications including structural fuses and retrofitting of reinforced concrete members etc. In this paper, mechanical properties of HPFRCC materials are reviewed briefly. Moreover, a reinforced concrete beam (experimentally tested by Maalej et al.) is chosen and in different specimens, lower or upper or both parts of that beam are replaced with HPFRCC layers. After modeling of specimens in ABAQUS and calibration of those, mechanical properties of these specimens are investigated with different thicknesses, tensile strengths, tensile strains and compressive bars. Analytical results which are obtained by nonlinear finite analyses show that using HPFRCC layers with different parameters, increase loading capacity and ultimate displacement of these beams compare to RC specimens.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.290-295
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• 2000

Mechanical and physical properties of wood fiber for the reinforcement of thin-sheet cement products were investigated. The slurry-dewatering method followed by pressing was used to manufacture the products. Mechanical and physical properties of wood fiber reinforced cement composites were assessed with flexural strength, density, and water absorption. The results obtained in this study were analyzed statistically using the analysis of variance in order to derive statistically reliable conclusions.

• 대한토목학회논문집
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• 제26권6A호
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• pp.1033-1039
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• 2006

본 연구의 목적은 1.8 mm의 높이와 6 mm의 주기를 가지고 있는 crimped type 합성섬유로 보강된 시멘트 복합재료의 부착 및 휨특성과 소성수축균열제어 특성을 평가하는 것이다. 부착 및 휨 시험은 JCI SF-4 및 JCI SF-8에 의해서 실시하였고, 소성수축균열시험은 시멘트 복합재료의 소성수축균열의 감소에 영향을 미치는 섬유의 효과를 평가하기 위하여 실시하였다. 실험결과 crimped type 합성섬유는 직선형태의 섬유와 비교하여 부착하중 및 계면인성이 우수하였고, 콘크리트의 휨인성을 증가시켰다. 또한 crimped type 합성섬유는 섬유의 혼입율이 0.00%에서 1.00%로 증가함에 따라 소성수축균열 저항성이 증가하였다. 특히, 섬유의 혼입율이 0.50% 이상이 되면 소성수축균열 조절능력이 매우 우수하였다.

• 한국세라믹학회지
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• 제34권5호
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• pp.491-499
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• 1997

High flexible lightweight composites containing tobermorite as a main mineral is produced using various amorphous silicates, lime, cement and fibers. Here, Mechanical properties of the composites were studied by observing microstructures of hydrates and fibers. Amorphous silicates having better hydraulicity retarded the crystallization of tobermorite due to better formation of C-S-H gel in water bath curing, but, difficult conversion from C-S-H gel to tobermorite in hydrothermal reaction. In the low molar ratio of CaO/SiO2 (0.67), faster crystalization was observed dued to more impurities such as Al2O3 alkali, resulting in improving mechanical properties due to small crystal size and many contact points. It was identified that a lot of calcium silicate hydates formed at surface of pulps increase bonding strength and the crack-resistance of matrix in the composites, but decrease hardness and compressive strength. The choice of amorpous silicates having better hydraulicity, low CaO/SiO2 adding each fibers bellow about 5% in the raw mixs and lower molding pressure should be needed at improve mechanical properties of composites.

• The Korean Journal of Ceramics
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• 제6권3호
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• pp.201-205
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• 2000

Fiber reinforced plastic (FRP) composites and ceramic matrix composites (CMC) which contain electrically conductive phases have been designed and fabricated to introduce the detection capability of damage/fracture detection into these materials. The composites were made electrically conductive by adding carbon and TiN particles into FRP and CMC, respectively. The resistance of the conductive FRP containing carbon particles showed almost linear response to strain and high sensitivity over a wide range of strains. After each load-unload cycle the FRP retained a residual resistance, which increased with applied maximum stress or strain. The FRP with carbon particles embedded in cement (mortar) specimens enabled micro-crack formation and propagation in the mortar to be detected in situ. The CMC materials exhibited not only sensitive response to the applied strain but also an increase in resistance with increasing number of load-unload cycles during cyclic load testing. These results show that it is possible to use these composites to detect and/or fracture in structural materials, which are required to monitor the healthiness or safety in industrial applications and public constructions.