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RISS 인기검색어
- 검색키워드
- 저자 : Seongwoo Gwon (검색결과 14 건)
- 무료
- 기관 내 무료
- 유료
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Gwon, Seongwoo,Jang, Seung Yup,Shin, Myoungsu Elsevier 2018 Construction and Building Materials Vol.192 No.-
<P><B>Abstract</B></P> <P>Ultra rapid hardening (URH) cement is used where ultra high early strength is required in construction. This study investigated the age-dependent characteristics of calcium sulfoaluminate (CSA)-based URH cement modified by the addition of acrylic redispersible polymer powder. Specifically, the effects of polymer powder on the microstructure evolution and strength development were examined from an early age of 2 h up to 90 days. The macro- and microstructural properties of various cement paste, mortar, and concrete samples were characterized by compressive strength, rheology, mercury intrusion porosimetry, powder X-ray diffraction, and scanning electron microscopy with energy-dispersive spectroscopy. The test results revealed that increasing the polymer proportion up to 10% by mass of cement not only delayed the setting and hydration, but also refined the pore structures of the URH cement systems, which is considered the main cause of the long-term strength convergence of the mortars with different polymer ratios. The polymer addition induced the formation of more ordered and denser ITZs between the mortar and coarse aggregate. All findings support the favorable effects of the polymer powder on the long-term strength and durability of the URH cement systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effects of polymer on the microstructure evolution and strength development were examined from 2 h to 90 days. </LI> <LI> Increasing the polymer proportion up to 10% delayed the setting and hydration and reduced the early strength. </LI> <LI> The long-term strengths of mortars exhibited convergence regardless of the polymer ratio. </LI> <LI> The polymer addition induced the formation of more ordered and denser ITZs between the mortar and coarse aggregate. </LI> </UL> </P>
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Strength and toughness of hybrid steel and glass fiber-reinforced sulfur polymer composites
Gwon, Seongwoo,Kim, Seungpil,Ahn, Eunjong,Kim, Chanyoung,Shin, Myoungsu Elsevier BV 2019 Construction and Building Materials Vol.228 No.-
<P><B>Abstract</B></P> <P>In this study, we investigated the effects of microfibers on the compressive and flexural behaviors of modified sulfur composites. Dicyclopentadiene-modified sulfur was used as the binder in the sulfur composites. Fifteen mix cases were tested by varying the volumetric ratios of steel and electric chemical resistant glass fibers. Fly ash (35% by volume) was included to not only increase strength and workability, but also ensure fiber dispersibility in the matrix. A non-contact displacement measurement technique, digital image correlation, was used in flexure tests to monitor the development of high strain zones and microcracks. The effect of fiber dosage on the porosity of sulfur composites was analyzed by quantifying the pore volume and size distribution through mercury intrusion porosimetry. The test results confirmed that the hybrid use of steel and glass fibers with a volume ratio of up to 4% was effective in improving the flexural stress-deflection response. The post-peak toughness ratio in flexure increased as the volume of microfibers increased. In addition, the total volume of hybrid microfibers generally had a positive correlation with the flexural strength. In contrast, the compressive strength of hybrid fiber-reinforced sulfur composites was more dependent on the portion of steel fibers than glass fibers.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The behaviors of microfiber-reinforced modified sulfur composites were investigated. </LI> <LI> The hybrid of steel and glass fibers was effective in improving flexural response. </LI> <LI> The post-peak toughness ratio in flexure increased according to more microfibers. </LI> <LI> The total volume of microfibers had a positive correlation with flexural strength. </LI> <LI> The compressive strength of sulfur composites was more dependent on steel fibers. </LI> </UL> </P>
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Gwon, Seongwoo,Shin, Myoungsu Elsevier 2019 Construction and Building Materials Vol.228 No.-
<P><B>Abstract</B></P> <P>This study investigates the effects of micro-filler characteristics and mixing temperature on the rheological properties of fresh modified sulfur polymer composites. Modified sulfur was used as the binder, and a blend of Portland cement and fly ash was used as the micro-filler in the sulfur composites. Different micro-filler volumetric ratios were used (15, 25, and 35%), and the composition ratios of Portland cement to fly ash used were 1:0, 3:1, 1:1, 1:3, and 0:1. Two temperatures, 120 and 140 °C, were selected considering that the temperatures of sulfur composites usually range from 120 to 140 °C at casting. Moreover, the correlation between mini slump flow and yield stress was examined. In addition, the compressive strengths of various hardened sulfur composites were compared with respect to the effect of micro-filler. An increase in the micro-filler volumetric ratio generally caused an exponential growth of both yield stress and plastic viscosity. The rheological properties generally increased as the cement-to-fly ash ratio increased, and this effect was distinct with 35% micro-filler. The increase in the mixing temperature from 120 to 140 °C caused a considerable increase in both yield stress and plastic viscosity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The rheological properties of fresh modified sulfur polymer composites were investigated. </LI> <LI> A blend of Portland cement and fly ash was used as the micro-filler in the sulfur composites. </LI> <LI> The increase of micro-filler volume ratio caused an exponential growth of yield stress and plastic viscosity. </LI> <LI> The rheological properties generally increased as the cement-to-fly ash ratio increased. </LI> <LI> The change of mixing temperature had a significant effect on the rheological properties. </LI> </UL> </P>
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Nonlinear modeling parameters of RC coupling beams in a coupled wall system
Gwon, Seongwoo,Shin, Myoungsu,Pimentel, Benjamin,Lee, Deokjung 테크노프레스 2014 Earthquakes and structures Vol.7 No.5
ASCE/SEI 41-13 provides modeling parameters and numerical acceptance criteria for various types of members that are useful for evaluating the seismic performance of reinforced concrete (RC) building structures. To accurately evaluate the global performance of a coupled wall system, it is crucial to first properly define the component behaviors (i.e., force-displacement relationships of shear walls and coupling beams). However, only a few studies have investigated on the modeling of RC coupling beams subjected to earthquake loading to date. The main objective of this study is to assess the reliability of ASCE 41-13 modeling parameters specified for RC coupling beams with various design details, based on a database compiling almost all coupling beam tests available worldwide. Several recently developed coupling beam models are also reviewed. Finally, a rational method is proposed for determining the chord yield rotation of RC coupling beams.
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Gwon, Seongwoo,Ahn, Eunjong,Shin, Myoungsu Elsevier 2019 Composites Part B, Engineering Vol.162 No.-
<P><B>Abstract</B></P> <P>This study investigated the applicability of calcium sulfoaluminate (CSA)-based cement and superabsorbent polymer (SAP) to the self-healing of modified sulfur composites. Modified sulfur was used as a binder in the sulfur composites. Eight different mixtures were tested by varying the ratio between CSA expansive agent and Portland cement in the CSA-based binary cement, with or without the addition of SAP. A series of nondestructive evaluation analyses, including optical microscopy, computed tomography, and elastic wave transmission, confirmed the synergetic effect of the CSA cement and SAP on the self-healing of modified sulfur composites in wet environments. Both the CSA cement and SAP remained intact in the hardened sulfur composites, but after crack generation and water infiltration, hydrated cement phases and/or swollen SAP particles were produced in the crack gap. The crack-sealing progressed faster and tighter as the portion of CSA expansive agent increased in the binary cement. In addition, the use of SAP greatly escalated the self-healing performance. The reaction products newly formed in the crack gap reflected the self-healing mechanism of the sulfur composites.</P>
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Gwon, Seongwoo,Jeong, Yeonung,Oh, Jae Eun,Shin, Myoungsu Elsevier 2017 Construction & building materials Vol.135 No.-
<P><B>Abstract</B></P> <P>Sulfur polymer concrete (SPC) is a thermoplastic composite that is generally composed of modified sulfur polymer binder and aggregate. This study proposed a new approach for developing sustainable sulfur composites by using only hazardous industrial wastes without aggregate. The industrial wastes used in this study were sulfur, fly ash, and rubber powder from waste tires. The proposed method may have several major advantages compared to using cement-based concrete as well as traditional SPC: less CO<SUB>2</SUB> emissions, lower life-cycle cost, and superior durability. To examine the effects of waste rubber powder and fly ash on the strength and microstructure of sulfur composites after three days of curing, a series of characterization analyses were conducted based on the tests of compressive strength, powder X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, and mercury intrusion porosimetry. The test results suggested that the replacement of sulfur with fly ash up to about 45% generally improved the compressive strength of sulfur composites, and rubber powder effectively substituted fine aggregate or a portion of sulfur without significant strength reduction. This study also revealed that the microstructure of sulfur composites was significantly affected by varying the amounts of fly ash or rubber powder, despite no change in reaction products.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The highest strength was achieved when 50% of modified sulfur was replaced by fly ash. </LI> <LI> With more than 40% fly ash, the microstructure of sulfur matrix was completely changed. </LI> <LI> At a low ratio of fly ash, the use of 5–10% rubber powder enhanced the strength of sulfur composites. </LI> <LI> Sulfur mortars with 5–10% sand showed lower strengths than sulfur composites with rubber powder. </LI> <LI> The sulfur composites had very low porosities, and the use of fly ash reduced the porosity. </LI> </UL> </P>
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Gwon, Seongwoo,Oh, Seok-Young,Shin, Myoungsu Elsevier 2018 Construction & building materials Vol.181 No.-
<P><B>Abstract</B></P> <P>This study investigated the strength and microstructural characteristics of modified sulfur polymer composites employing several industrial wastes (such as sulfur and rubber) and binary cement (blend of fly ash and Portland cement) as primary components. Modified sulfur played a role of a binder in the sulfur composites. Portland cement was blended together with fly ash in the binary cement that was used as a micro-filler, as well as a potential crack-healing agent, in the sulfur composites. Rubber powder from waste scrap tires was used as a substitute of fine aggregate. A total of 24 different mixtures were tested by varying the mix proportions of sulfur, binary cement, and rubber powder. The test results revealed that the highest compressive strength of the sulfur composites for a given rubber powder ratio was acquired from the use of 40% binary cement ratio. A broad series of microstructural analyses, including SEM, XRD, and FT-IR spectroscopy, confirmed the beneficial effect of the binary cement (up to 40%) on the strength of the sulfur composites, and supported its potential role in crack healing.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Portland cement was blended with fly ash in the binary cement as a potential crack-healing agent. </LI> <LI> The highest strength of sulfur composites was acquired from 40% binary cement ratio. </LI> <LI> The beneficial effect of the binary cement on the strength of sulfur composites is identified. </LI> <LI> Microstructural analyses support the potential role of the binary cement in crack healing. </LI> </UL> </P>
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권성우 ( Gwon Seongwoo ),신명수 ( Shin Myoungsu ) 한국구조물진단유지관리공학회 2023 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.27 No.1
시멘트 복합체는 탄소 계열 전도성 소재를 일정 임계치 이상 포함하면 낮은 저항을 보유할 수 있다. 이러한 전기전도성 시멘트 복합체는 낮은 전기 저항과 줄 발열 원리를 토대로 전압 인가 시 자체 온도가 증가한다. 기존 선행 연구들은 탄소나노튜브를 주요 소재로 사용하였는데 이 비싼 재료는 토목 및 건축 분야에 실질적으로 적용하기에 한계가 있다. 본 연구는 중질 원유 제품의 불완전 연소로 발생하는 카본블랙을 주요 전도성 소재로 채택하고 탄소섬유를 동시 혼입하여 시멘트 복합 체의 낮은 전기 저항을 확보하였다. 낮은 전기 저항을 보유한 배합들은 전압 인가 시 우수한 발열 특성을 나타냈다.
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