• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.1
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• pp.25-32
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• 2005

This study was performed to evaluate strengths and non-destruction properties of super flow concrete using recycled coarse aggregate. At the curing age of 28 days, the compressive strength was 22.7-37.5 MPa, the splitting tensile strength was $2.65\~3.73$ MPa, the flexural strength was $5.78\~6.86$ MPa, the ultrasonic pulse velocity was $3,103\~3,480$ mis, the dynamic modulus of elasticity was $3.401{\times}104\~4.521{\times}104$MPa, respectively. The strengths, ultrasonic pulse velocity and dynamic modulus of elasticity of super flow concrete were decreased with increasing the content of recycled coarse aggregate. The super flow concretes using recycled coarse aggregate were improved by substitution in the range of less than the fly ash content 30010 and recycled coarse aggregate content $75\%$.

• Journal of Technologic Dentistry
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• v.39 no.2
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• pp.83-91
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• 2017

Purpose: The objective of this study was to evaluate influence of mechanical properties of gingival shade composite resins(GSCRs) according to thermocycling treatment. Methods: The material utilized in this study was Crea.lign(CGR), Twiny flow(TGF) and Twiny(TGP). Total sixty specimens were fabricated with a dimension of $25{\times}2{\times}2mm$ according to the ISO 4049. After fabrications, specimens of before and after thermocycling(to $55^{\circ}C$ from $5^{\circ}C$) were stored in the distilled water for 24 hours at the $37^{\circ}C$. Three-point flexural test was performed in universal testing machine(Instron 5966, USA) at a crosshead speed of 1 mm/min. Flexural strength, flexural modulus and work of fracture according to the thermocycling were analyzed using a one-way ANOVA analysis. Surface analysis of GSCRs after thermocycling evaluated using the scanning electron microscope. Results: : The highest FS was measured in TGP group of NTC group and lowest in CGR group after TC. After TC, FS and FM decreased in CGR and TGP groups, but TGF increased. There was a statistically significant difference between FS and WOF in GSCRs(p<0.05). But FM did not show any significant difference after TC (p>0.05). The strength of the characteristic exceeded the flexural strength required by ISO 4049(> 80 MPa). Weibull modulus(m) showed the highest reliability in the TGP group (m = 14.22), and the reliability of the TGF and TGP groups after TC decreased. Conclusion: Thermocycling treatment is important factor influence of mechanical properties with gingival shade composite resins. Therefore, we recommended that mechanical properties need to get useful information and accuracy for life-span expectancy according to the thermocycling treatment.

• Journal of the Korean Ceramic Society
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• v.50 no.5
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• pp.341-347
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• 2013

Kaolin-based membranes with a pore size of 0.30-0.40 ${\mu}m$ were successfully prepared by a simple pressing route using low-cost starting materials, kaolin and sodium borate. The prepared green bodies were sintered at different temperatures ranging between 900 and $1200^{\circ}C$. The sintered membranes were characterized by X-ray diffraction, mercury porosimetry, scanning electron microscopy, and capillary flowmetry. It was observed that the porosity decreased with an increase in both the sintering temperature and the sodium borate content, whereas the flexural strength increased with an increase in both the sintering temperature and the sodium borate content. The air flow rate decreased with an increase in the sodium borate content. The typical porosity, flexural strength, and specific flow rate of the kaolin-based membrane sintered with 5 wt% sodium borate at $1100^{\circ}C$ were 37%, 19 MPa, and $1{\times}10^{-3}L/min/cm^2$, respectively, at a p of 30 psi.

• Polymer(Korea)
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• v.24 no.1
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• pp.38-47
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• 2000

A study of linear and branched polycarbonates blend system is presented. Flow and mechanical properties, and miscibility were studied for the blends of various compositions. No phase separations were observed in the blend systems. The mechanical properties of blends were examined through tensile strength, tensile modulus, flexural strength, flexural modulus and impact strength. Melt viscosity, storage and loss moduli of the blends with various compositions were examined at various temperatures. The dependence of viscosity on molecular weight was also presented. Flow properties of the blends showed significant variations however, mechanical properties were relatively independent of the compositions. As the content of branched polycarbonate increased, the dependence of viscosity on molecular weight and shear thinning behavior became more marked. Therefore the blend systems which have same mechanical properties but different flow properties can be obtained.

• Journal of dental hygiene science
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• v.15 no.4
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• pp.407-412
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• 2015

This study investigated flexural properties of indirect Gum-shade composite resins for esthetic improvement. The material utilized in this study was Crea.lign, Twiny flow and Twiny paste (TP). Ten specimens were fabricated with a dimension of $25{\times}2{\times}2mm$ according to the ISO 4049. After fabrications, specimens were stored in the distilled water for 24 hours at the temperature of $37^{\circ}C$. Three-point bending test was performed in universal testing machine (Instron 3344; Instron, USA) at a crosshead speed of 1 mm/min until the failure occurred. TP exhibited a higher flexural strength (FS) and flexural modulus (FM) compared to the flowable materials. There were significant differences among the three materials in FS and FM. However, there was no significant difference in work of fracture (WOF) in all tested materials (p>0.05). In Weibull analysis, TP showed the greatest Weibull modulus which means a higher reliability of the materials. Also, Gum-shade composite resins revealed a strong correlation in all flexural properties. There was a positive correlation in FS-FM ($r^2=0.99$) and a negative correlation between FS-WOF and FM-WOF ($r^2>0.97$). Therefore, this confirmed that flexural property was important for mechanical behavior evaluation and useful information. To addition, this improved among mechanical properties correlation of materials as important factor.

• Advances in concrete construction
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• v.5 no.1
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• pp.31-48
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• 2017

Supplementary cementitious materials (SCM) have turned out to be a vital portion of extraordinary strength and performance concrete. Metakaolin (MK) is one of SCM material is acquired by calcinations of kaolinite. Universally utilised as pozzolanic material in concrete to enhance mechanical and durability properties. This study investigates the fresh and hardened properties of conventional concrete (CC) and self compacting concrete (SCC) by partially replacing cement with MK in diverse percentages. In CC and SCC, partial replacement of cement with MK varies from 5-20%. Fresh concrete properties of CC are conducted by slump test and compaction factor tests and for SCC, slump flow, T500, J-Ring, L-Box, V-Funnel and U-Box tests. Hardened concrete characteristics are investigated by compressive, split tensile and flexural strengths at age of 7, 28 and 90 days of curing under water. Carbonation depth, water absorption and density of MK based CC and SCC was also computed. Fresh concrete test results indicated that increase in MK replacement increases workability of concrete in a constant w/b ratio. Also, outcomes reveal that concrete integrating MK had greater compressive, flexural and split tensile strengths. Optimum replacement level of MK for cement was 10%, which increased mechanical properties and robustness properties of concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.3
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• pp.210-217
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• 2023

Various performances of ultra-high performance concrete (UHPC) applied with microplastics and expanded polystyrene (EPS) beads were evaluated. CompressIve and flexural strength, performance after ignition, flow-down in fresh state, and effective bond strength were evaluated. Designed weight of the cement panel with these mixtures was calculated based on the flexural strength. As a result of the experiments, it was confirmed that the EPS could reduce the density of UHPC with largest range. By maximum addition of EPS beeds, the density of UHPC decreased to 1300 kg/m³, and the compressive and flexural strengths for this mixtures were in ranges of 20-30 MPa and 15-20 MPa, respectively. On the other hand, lightest cement panel could be designed with UHPC having a density ranges about 2.0 g/cm³.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.5
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• pp.79-85
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• 2004

This study was performed to evalute mechanical and drying shrinkage properties of polypropylene fiber reinforced high flow concrete. The compressive strength and drying shrinkage ratio were increased with increasing the binder volume ratio and decreased with increasing the content of polypropylene fiber. The splitting tensile strength was increased with increasing the binder volume ratio and the content of polypropylene fiber. The flexural strength was increased with increasing the binder volume ratio and increased by the polypropylene fiber content 0.4%, but above the polypropylene fiber content 0.6% was decreased. This concrete can be used for high flow concrete.

• Journal of Ship and Ocean Technology
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• v.6 no.2
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• pp.1-11
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• 2002

For the analysis of vibrational energy density and intensity of partitioned complex system structures in medium-to-high frequency ranges, A software based on the Power Flow Analysis(PFA) has been developed for the plate elements. The flexural, longitudinal and shear waves in plates are formulated and the joint element equations for multi-coupled plates are fully developed. Also, the wave transmission approach has been introduced to cover the energy transmission and reflection at the joint plate elements. To confirm the validity of the developed PFA software, the submarine-shaped complex structures are used for the analysis of vibration intensity and energy density.

• Journal of the Korea Institute of Building Construction
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• v.21 no.1
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• pp.1-10
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• 2021

The purpose of this study is to evaluate the improvement of flow, compressive and flexural strengths of polymer cement mortar(PCM) using SBR latex mixed with blast-furnace slag and fly ash. The test specimens were prepared with SBR polymer dispersion, two types of admixture (blast-furnace slag and fly ash), five polymer-cement ratios (P/C; 0, 5, 10, 15 and 20%), and six admixture contents (0, 3, 5, 10, 15 and 20%), plain cement mortar was also made for comparison. From the test results, the flow of PCM was significantly improved compared to ordinary cement mortar, but the flow was slightly reduced when mixed with blast-furnace slag, and the flow was similar to PCM when mixed with fly ash. In addition, the compressive strength of PCM mixed with admixtures was significantly improved, but the flexural strength did not improve except for some mortars. It can be stated that the optimum mix proportions of PCM using SBR with admixture contents 10 to 15% and P/C 10% for the compressive strength improvement, and P/C 20% for flexural strength improvement are recommended respectively in this study.