• 한국세라믹학회지
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• 제31권9호
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• pp.941-948
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• 1994

An underwater grout on material resistance against segregation in water were studied by water soluble polymer (methyl cellulose and acrylic acid ester and styrene). The mechanical properties of the grout agents were investigated through the observation of the microstructure and application of fracture mechanic. When the soluble polymer MC+AAES added with 0.6 wt% to the underwater grout agents the compressive strength, flexural strength and Young's modulus were about 58 MPa, 10 MPa and 3.2 GPa respectively, and critical stress intensity was about 0.8 MNm-1.5. It can be considered that the strength improvement and fracture toughness increase may be due to the pore decrease and bonding force by material resistance against segregation in water.

• Computers and Concrete
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• 제17권5호
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• pp.597-612
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• 2016

The present work focuses on the use of coconut fiber in self compacting concrete. Self-Compacting Concrete (SCC) is a highly flowable, stable concrete which flows readily into place, filling formwork without any consolidation and without undergoing any significant segregation. Use of fibers in SCC bridge the cracks and enhance the performance of concrete by not allowing cracks to propagate. They contribute to an increased energy absorption compared to plain concrete. Coconut fiber has the highest toughness among all natural fibers. It is known that structures in the seismic prone areas are always under the influence of cyclic loading. To justify the importance of strengthening SCC beams with coir fiber, the present work has been undertaken. A comparison is made between cyclic and static loading of coconut fiber reinforced self compacting concrete (FRSCC) members. Using the test data obtained from the experiment, hysteresis loops were drawn and comparison of envelope curve, energy dissipation, stiffness degradation were made and important conclusions were draw to justify the use of coconut fiber in SCC.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2003년도 학술발표논문집
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• pp.367-370
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• 2003

Lightweight polymer concrete with steel fiber can be used for thin panel, high building and large span structures due to its may advantages such as its durability, low weight, control of crack propagation, high strength and toughness. This study experimented about steel fiber reinforcement of lightweight polymer concrete using synthetic lightweight aggregate. The test result shows that the maximum strain and elastic modulus are in the range of $0.012{\sim}0.014\;and\;50.2{\times}10^3{\sim}51.0{\times}10^3kgf/cm^2$, respectively. The flexural load-deflection curves after maximum load are shown in smoothly with increase of steel fiber content

• 한국세라믹학회지
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• 제31권7호
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• pp.745-752
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• 1994

A polymer reinforced grouts using ordinary portland cement mortar and water soluble polymer{polyvinyl alcohol(PVA), styrene-butadiene rubbre(SBR), etylene-vinyl acetate copolymer(EVA)} were made. The mechanical properties of the hardened specimens were investigated through the observation of the microstructure and application of fracture mechanics. When the PVA, SBR and EVA was added with 1.5 wt% to the grouts, the compressive strength were about 54 MPa, 63 MPa and 68 MPa respectively, and the flexural strength was about 11 MPa, 12.8 MPa, and 13.6 MPa respectively, and Young's modulus was about 3.8 GPa, 4.4 GPa and 4.6 GPa respectively, and critical stress intensity was about 0.73 MNm-1.5, 0.85 MNm-1.5 and 0.9 MNm-1.5 respectively. It can be considered that the strength improvement of polymer mortar grouts may be due to the removal of macropores and the increase of various fracture toughness effects, such as grain bridging, frictional interlocking and polymer bridging.

• The Korean Journal of Ceramics
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• 제1권2호
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• pp.101-105
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• 1995

Electrical discharge machinable $Si_3N_4$ was fabricated with the addtion of 20-60 vol% TiN by gas pressure sintering. Their sinterability, microstructure, mechanical and electrical properties were characterized as a function of the TiN content. The addition of TiN up to 20 vol% increased the flexural strength and fracture toughness as compared with those of the monolithic Si3N4. For the TiN content higher than 40 vol%, the electrical resistivity was lower than $1062\Omega$.cm. The $Si_3N_4$ with the addition of 40 vol% of TiN appears to have the optimum considerable sinterability, mechanical and electrical properties, and machinability. A microstructural analysis showed that the enhanced toughening was due to the crack deflection.

• 한국세라믹학회지
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• 제28권9호
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• pp.696-704
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• 1991

ZrO2-Toughened Alumina-Ceramics (ZTA) with SiC Whisker as dispersive additive were prepared by pressureless sintering at 1$600^{\circ}C$ and 1$650^{\circ}C$ and by HIPing at 1$600^{\circ}C$ in Ar atmosphere. Effects of SiC-Whisker addition on microstuructural, mechanical, and thermal properties were investigated and the toughening mechanisms between theory and experiment were compared. Specimens with 15 vol% Whisker prepared by HIPing showed 8.26 MPa.ma1/2 in fracture toughness and 600 MPa in flexural strength owing to contribution of the three mechanisms such as crack deflection, whisker bridging and whisker pullout in spite of difference between the theoretical and experimental values due to the partial inhomogeneous dispersion of SiC-Whisker in the matrix and the processing flaw.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1433-1435
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• 2001

The mechanical and phase transformation of the cold isostatically pressed $\beta$-SiC ceramic were investigated as a function of the sintering temperature. The result of phase analysis revealed 6H, 4H, 3C and phase transformation between 3C and 4H showed over 2000$^{\circ}C$ and the $\beta$ ${\rightarrow}$ $\alpha$ phase transformation was in saturation at 2200$^{\circ}C$. The relative density and the mechanical properties of $\alpha$-SiC ceramic was increased with increased sintering temperature. The flexural strength showed the highest value of 230 MPa at 2200$^{\circ}C$. This reason is because crack was propagated through surface flaw. The fracture toughness showed the highest value of 4.2 $MPa{\cdot}m^{1/2}$ at 2200$^{\circ}C$.

• 한국세라믹학회지
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• 제30권2호
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• pp.139-147
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• 1993

Two sheets of high strength cement paste using ordinary Portland cement and water soluble polymer (polyacrylamide) were made by kneading with a twin roll mill. A carbon fiber layer out between two sheet of the cement paste, and then carbon fiber reinforced high strength cement composites were prepared by pressing them. The mechanical properties of the composites were investigated through the observation of the microstructure and the application of fracture mechanics. When the carbon fiber was added with 0.2 and 0.3wt% to the composites the flexural strength and Young's modulus were about 110∼116MPa and 74∼77GPa respectively, and critical stress intensity was about 3.14MPam1/2. It can be considered that the strength improvement of high strength cement fiber composites may be due to the removal of macropores and the increase of various fracture toughness effects; grain bridging, frictional interlocking, polymer fibril bridging and fiber bridging.

• Smart Structures and Systems
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• 제19권3호
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• pp.323-333
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• 2017

Waste materials in concrete have been considered as one of the most important issues by the authorities, policy makers and researchers to maintain engineering serviceability in terms of economy, durability and sustainability. Therefore, evaluation and selection of waste materials with respect to multi criteria decision making (MCDM) for the construction industry has been gained importance for recovery and reuse. In this paper, Choquet integral based fuzzy approach is proposed for evaluating the most suitable waste materials with respect to compressive strength, tensile strength, flexural strength, compactness, toughness (resistivity for dynamic loads), water absorption and accessibility. On conclusion, waste tyre and silica fume were determined as the most suitable waste materials for concrete production. The obtained results are recommended to assist the authorities on configuring well designed strategies for construction industry with disposal materials.

• 한국세라믹학회지
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• 제31권5호
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• pp.491-498
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• 1994

A fiber reinforced grouts were made using ordinary cement mortar and high effective water reducing agent (naphthalene sulfonate) were made by addition polypropylene fiber and carbon fiber. The physical properties of the grouts were investigated through the observation of the microstructure and the application of fracture mechanics. When the polypropylene fiber and carbon fiber were added respectively with 0.03 wt% to the grouts the compressive strength, flexural strength and Young's modulus were about 60∼63 MPa, 12.2∼12.4 MPa, 4.2∼4.8 GPa and 63∼68 MPa, 12.2∼12.6 MPa, 4.8∼5.1 GPa, and critical stress intensity were about 0.77∼0.82 MNm-1.5, and 0.80∼0.87 MNm-1.5 respectively, It can be considered that the strength improvement of fiber reinforced grouts (FRG) may be due to the removal of macropores and the increase of various fracture toughness, polymer fibril bridging and fiber bridging.