• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.124-125
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• 2014

Polymer concrete has more excellent durability, tensile strength, flexural strength and waterproof performance mechanically than normal concrete, and as it mixes as a polymer binding material, it can reduce the cement use amount. This study reviews fundamental properties of cement material mixed with complex polymer. As a result of this study, as percentage of complex polymer mix increases, flow value will decrease so that liquidity and compression strength will decrease. On the other hand, in case of flexural strength, when the mixture is 10%, it increases significantly more than OPC.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.216-219
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• 2004

The stitching process has been widely utilized for the improvement of through-thickness property of the conventional laminated composites. This paper rep0l1s the effects of stitching on the flexural and interlaminar shear properties of multiaxial warp knitted composites in order to examine the performance improvements. Considered parameters are as follows: the stacking regularity of the multiaxial warp knits, the stitch spacings, the stitching types, the stitching location, and the location of compression fixture nose. These parameters have little effect on the flexural and interlaminar shear properties, except for the case of stitching location. Stitching on the $0^{\circ}$ fibers showed the lowest flexural strength and modulus ($12\%$reduction for both properties). The stitch spacing of 5mm resulted 8% reduction in interlaminar strength compared with 10mm spacing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.3 s.234
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• pp.425-431
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• 2005

The efficiency of complex slurry preparation route for developing the high performance SiC matrix of $RS-SiC_{f}/SiC$ composites has been investigated. The green bodies for RS-SiC materials prior to the infiltration of molten silicon were prepared with various C/SiC complex slurries, which associated with both the sizes of starting SiC particles and the blending conditions of starting SiC and C particles. The characterization of Rs-SiC materials was examined by means of SEM, EDS and three point bending test. Based on the mechanical property-microstructure correlation, the process optimization is also discussed. The flexural strength of Rs-SiC materials greatly depended on the content of residual Si. The decrease of starting SiC particle size in the C/SiC complex slurry was effective for improving the flexural strength of RS-SiC materials.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.25-29
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• 2003

In the semiconductor and the optical industry a new transport system which can replace the conventional sliding system is required. These systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system can solve these problem. In this paper, the object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal excitation frequency, finding phase-difference between two ultrasonic wave generators are performed. The relationship of transporting speed according to the change of flexural beam shape is verified and the system performance for practical use is evaluated.

• Steel and Composite Structures
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• v.21 no.4
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• pp.775-789
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• 2016

This paper presents the flexural behavior & ultimate strength performance of innovative light weight sandwich panels of size $3{\times}1.2m$ with two different solidity ratios viz. 0.5 and 0.33 under out of plane bending load. From the experimental studies, it is observed that the flexural strength and the stiffness are increased by about 46% and five folds for lesser solidity ratio case. From the measured strains of the shear connectors, full shear transfer between the concrete wythes is observed. The yielding occurred approximately at 4% and 0.55% of the ultimate deformation for 100 mm & 150 mm thick panels, which shows the large ductility characteristics of the panels. From the study, it is inferred that the light weight sandwich panels behave structurally in a very similar manner to reinforced concrete panels. Further from the numerical study, it is observed that the numerical values obtained by FE analysis are in good agreement with the experimental observations.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.04a
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• pp.59-62
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• 2007

Nowadays, polymer-cement mortars are widely used in construction field(floorings and pavements, water-proofings, adhesives, repair materials, deck coverings, anti-corrosive linings) Because of excellent performance such as high tensile and flexural strength, waterproofness, excellent adhesion, good durability, improved wear and chemical resistances. This article presents the results of experimental study that investigates the effect of ambient temperature on the strength properties of polymer-modified cement mortar. Results show that when increasing the polymer proportion in mortar on different ambient temperature, the compressive strength and flexural strength are decreased, and also alkali resistance is decreased.

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.3_4
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• pp.90-98
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• 1995

The recycled concrete, average compressive strength of which was 2l0kg/cm$^2$ or higher with slump range of 14~18cm, was prepared by replacing 25% and 50% by weight of coarse aggregate with recycled aggregate from waste concrete. Mix design method for crushed aggregates was used and all specimens were cured by normal moisture curing method. A plasticiser and a fly ash were added to the mix to improve performance of recycled concrete. Flexural strength, stress- strain relationship and fracture toughness were evaluated by comparing with those of normal concretes. Recycled concrete showed, in general, lower flexural strength and fracture toughness, and higher strain under the same stress level. Fly ash in the concrete had an effect of reducing the strength and fracture toughness on both normal and recycled concretes. Since fly ash is known to improve many properties of concrete, while reducing strength properties, decision for using fly ash should be made carefully depending on the intended usage of the recycled concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.151-154
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• 2005

One of the most important characteristics of Engineered Cementitious Composite (ECC) is its strain hardening behavior up to $5\∼6\%$of stain under a tensile loading. So, the ductile behavior of ECC should be utilized in applications to maximize the performance of structures. Thus, in this study, the ductile behavior of ECC as a repair material applied to the tensile region under flexural loads is numerically examined using a developed numerical model. Several strain capacities of ECC are examined to predict the behavior of ECC strengthened flexural structures. The results show that a certain optimal level of ductility in ECCs for repair applications exists and it is an important factor to consider when using ECC as a repairing material.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.177-180
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• 2006

Experimental study has been performed in order to evaluate the effects of steel reinforcement ratio on the flexural behavior of RC beams strengthened with CFRP sheets. The steel reinforcement ratio of $0.78%({\rho}_s/{\rho}_b=24%)$ is selected to have balance failure when control RC beams were strengthened with 1 ply CFRP sheet. Total 6 half-scale specimens were manufactured including each unstrengthened specimens, which have 3 different reinforcement ratios. The specimens strengthened with CFRP sheet consist of under- or over-reinforced beams for the balanced failure condition. Moreover, the behavior of un strengthened or strengthened beams were compared to evaluate flexural performance. The results of this study show that the over-reinforced specimens were failed by concrete crushing prior to CFRP sheet failure by debonding or rupture. On the contrary, the under-reinforced specimen were failed by rupture of CFRP sheet.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.128-129
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• 2017

Concrete properties alone cannot provide satisfactory waterproof performance because concrete can generate cracks due to possible problems in design, construction and curing process, and various environmental factors. Therefore, concrete structures require installing waterproofing layers for concrete protection and various types of construction methods are currently being applied. The purpose of this study is to investigate the concrete strength changes when waterproofing admixtures are mixed into the concrete. The results of flexural strength testing confirmed that the initial strength of concrete specimens with the admixtures was lower than that of the concrete specimen without the admixture based on different curing periods.