• Applied Chemistry for Engineering
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• v.23 no.2
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• pp.210-216
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• 2012

For the recycling of rapid-cooled steel slag, various specimens were prepared with the various replacement ratios of the rapid-cooled steel slag and the addition ratios of polymer binders. The physical properties of these specimens were then investigated by absorption test, compressive strength test, flexural strength test and hot water resistance test, and the pore and the micro-structure analysis was performed using scanning electron microscope. Results showed that the flexural strength increased with the increase of rapid-cooled steel slag and polymer binder, but the compressive strength showed a maximum strength at a certain proportion. By the hot water resistance test, compressive strength and flexural strength decreased remarkably and the total pore volume increased but the pore diameter decreased. SEM observation of the structure before the hot water resistance test revealed a very compact infusion of structure but the decomposition or thermal degradation appeared in polymer binders when observed after the hot water resistance test.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.75-82
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• 2019

Slab panels are very important to develop asphalt concrete (AC) track for minimizing the roadbed stress due to the train load and reducing the plastic deformation of infrared-sensitive AC. In this study, the slab panel for AC track was developed through the shape design and the indoor performance test and its structural integrity has been investigated through the finite element analysis under the flexural tensile stress and the design moment according to various static load combination by KRL-2012 standard train load model and KR-C code. In order to verify the suitability of the slab panel for AC track, static bending strength test and dynamic bending strength test were performed according to EN 13230-2. Results show that the slab panel for AC track satisfies all the performance standards required by European standards such as crack loads and crack extension.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.4
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• pp.11-22
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• 2023

In this study, a structural concrete square beam was developed using the centrifugal molding technique. In order to secure the bending stiffness of the cross section, the hollow rate of the cross section was set to 10% or less. Instead of using the current poor mixture of concrete, a special formwork for producing a centrifugal square beam was manufactured, and a concrete mixing ratio with a high slump (150-200) and a design strength of 100 MPa or more was developed and applied. The produced centrifugally formed rectangular beams were subjected to performance tests according to the standard bending and shear test standards for centrifugally formed members. The static load test results for the four specimens exceeded both the nominal bending strength and nominal shear strength, which are design values through structural design, proving the structural reliability of the ultra-high-strength centrifugally formed square beam.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5A
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• pp.503-510
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• 2009

Latex modified concrete (LMC) is a successful polymer-portland cement concretes, which have been developed and used for many years, in overlaying bridge decks and resurfacing industrial floors. The excellent bond strength to substrate, easy application and high resistance to impact, abrasion, wear, aggressive chemicals and freeze-thaw deterioration have made this material used widely. The objective of this study was to determine experimentally the load-deflection response and ultimate strength of reinforced RC beams. The cracking patterns and the mode of failure were observed. Because of excellent bond strength and repairing effects, the RC beams repaired by LMC at compression or tension zone showed over 100% recovery from damaged structures. The RC beams overlaid by LMC showed significant improvement at load carrying capacity as overlay thickness increases. However, the beams repaired of tension zone without shear stirrups almost showed no strengthen effect, and indicated an interfacial failures. The interfacial behavior was estimated by numerical method adopting the concept of shear flow.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.271-278
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• 2019

The corrosion of reinforcements embedded in concrete causes severe deterioration in reinforced concrete structures. As a countermeasure, epoxy coated reinforcements are used to prevent corrosion of reinforcements. When epoxy coated bars are used, the resistance of corrosion is excellent, but epoxy coating on the bars have a disadvantage of reduction in bond capacity comparing to that of normal bars. Therefore, it is necessary to confirm the bond performance of epoxy coated reinforcements through experimental and analytical methods. Bond behaviors of epoxy coated bars for various diameters of 13 and 19mm and thicknesses of cover concrete of 3 types(ratio of cover to bar diameter) are examined. As the diameters of the epoxy coated bars increase, the difference of bond strength between epoxy coated and uncoated bars also increases and damage patterns showed pull out failure. In addition, finite element analysis was performed based on the bond-slip relationship obtained by direct pullout test and compared with the flexural test results. It is considered that flexural member test is more useful than pullout test for simulating the behavior of actual structure.

• Magazine of the Korea Concrete Institute
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• v.5 no.3
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• pp.179-186
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• 1993

본 연구는 무근 폴리에스터 폴리머 콘크리트보의 휨피로 거동을 구명키 위한 것으로서 초기균열깊이와 높이의 비 (a/h)를 0, 0.2, 0.4로 하고 응력수준을 45%, 55%, 65%로 하여 피로 시험을 실시한 것이다. 그 결과 초기균열깊이가 커질수록 피로수명이 짧아졌으며, 피로수명비에 따른 휨인장변형도는 균열깊이가 클수록 작아졌다. 또한 휨탄성계수는 피로수명비 0.2에서 0.6정도까지는 선형적인 변화를 보였으나, 초기와 말기에는 비선형적인 변화를 보여주었다. 그리고 응력수준과 균열깊이가 커질수록 취성적인 성질이 더 크게 나타남을 알 수 있었다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.134-142
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• 2020

In this study, in order to evaluate the self-healing performance of cement composites the self-healing test method and the analysis method were suggested by applying constant water head permeability test, chloride migration test and repeated bending test. The method of making a cracked specimen and controlling crack width are also proposed. Constant head water permeability test can evaluate the healing performance by using the decreasing rate of water flow passing through the crack zone of a specimen. Furthermore, the equivalent crack width can be used to intuitively investigate the healing effect with healing period. The chloride migration test can evaluate the healing rate by the decreasing rate of the diffusion coefficient obtained by ASTM C 1202. Mechanical healing performance can be evaluated using ISR and IDR estimated from load vs. CMOD relationship graph obtained through the repeated bending test. Finally, the applicability of proposed self-healing evaluation methods was examined by testing mortar specimens with or without self-healing agents.

• Journal of the Society of Disaster Information
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• v.11 no.4
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• pp.607-614
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• 2015

This study evaluated the flexural performance of steel and PP fiber reinfroced shotcrete using round panel test according to ASTM that can consider the actual stress of fiber reinforced shotcrete in tunnel and under ground structures. The results of round panel test are converted to the square panel test results according to the EFNARC. The energy absorptions of each fiber reinforced shotcrete were classified according to the EFNARC toughness classification. Test results show that the PP fiber reinforced shotcrete has better flexural performance compared with the steel fiber reinforced shotcrete.

• Journal of the Korea Concrete Institute
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• v.13 no.5
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• pp.466-475
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• 2001

The potential shear strength of reinforced concrete beams decreases after flexural yielding due to the decrease of the effective compressive strength of concrete in plastic hinge zone. A truss model considering shear deterioration in the plastic hinge zone was proposed in order to evaluate the ductile capacity of reinforced concrete beams failing in shear after flexural yielding This model can determine the potential shear strength of the beam by using a truss model. The potential shear strength gradually decreases as the increase of the axial strain of member. When the calculated potential shear strength decreases up to the flexural yielding strength, the corresponding rotation angle is defined as the ductile capacity of the beam. The predicted ductile capacity of reinforced concrete beams is shown to be in a good agreement with experimental results.

• Journal of Korean Society of Steel Construction
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• v.29 no.5
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• pp.353-359
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• 2017

The purpose of this study is to evaluate the strength and behavior of the composite member in case of concrete filled steel tube embedded in concrete for application concrete filled steel tube to steel rib support in tunnel. A total of six beam specimens were prepared for steel tube in-filled with plain concrete and aerated concrete, and static bending tests were performed. As a result, the member of concrete steel tube embedded with plain concrete showed higher strength than those with aerated concrete. However, it was found that the flexural strength of member with reinforcing bar around the steel tube is more influenced by the amount of the reinforcing bar than the type of the filled concrete.