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순환굵은골재를 사용한 레디믹스트 콘크리트의 역학적 특성
전에스더(Jeon Esther),윤현도(Yun Hyun-Do),지상규(Ji Sang-Kyu),최기선(Choi Ki-Sun),유영찬(You Young-Chan),김긍환(Kim Keung-Hwan) 대한건축학회 2009 大韓建築學會論文集 : 構造系 Vol.25 No.8
In this study, the mechanical properties of ready-mixed concrete with recycled coarse aggregate(RCA) were discussed. The mixing types were composed of twelve series based on specified compressive strength(i.e 21, 27, and 40MPa) and replacement ratio of recycled coarse aggregates(i.e 0, 30, 60 and 100%). Recycled coarse aggregate utilized in the study consists of 71.43% high quality recycled coarse aggregate, 28.57% low quality recycled coarse aggregate by weight. The properties of the fresh concrete were measured by means of slump and air content according to elapsed time. The strength properties of the hardened concrete were measured by means of compressive strength, splitting strength and modulus of rupture. Also test result were compared with existing domestic Codes(KBC2005 and KCI2007). Test result indicated that the replacement ratio of recycled coarse aggregate had little effect on fresh properties, such as slump and air content, of RCA concrete. Compressive strength, splitting strength and modulus of rupture of concrete is little affected by the replacement ratio of recycled coarse aggregate. And elastic modulus, splitting strength and modulus of rupture show relatively low values compared with relevant provisions in KBC2005 and KCI2007. Therefore, some design coefficients or recommendations in existing design code for natural aggregate concrete need to be amended for recycled aggregate concrete.
하이브리드 섬유를 혼입한 고인성 시멘트 복합체에서 철근의 겹침이음성능
전에스더 ( Jeon Esther ),김선우 ( Kim Sun-woo ),한병찬 ( Han Byung-chan ),양일승 ( Yang Il-seung ),윤현도 ( Yun Hyun-do ) 한국구조물진단유지관리공학회 2005 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.9 No.2
The objective of this study was to investigate the application of HPFRCC on tension lap splices with complex reinforcement. High performance fiber reinforced cementitious composite(HPFRCC) are characterized by a stress-strain response in tension that exhibits quasi strain-hardening behavior and multiple cracking. To meet the objective, ten specimens were tested. The variables were matrix[concrete, HPFRCC reinforced with polyethylene(PE), hybrid PE and steel cord(SC)], bar size(D16, 19, 22), lap splice length(60, 90% of standard lap splice length by ACI code) and loading type(monotonic, cyclic). Test results indicated that the use of PE and hybrid fibers in cementitious composites increased the tensile strength and the ductility of the mode of failure. Also, the presence of fibers increased the number of cracks formed around the lap splices, delayed the growth of the crack.
순환굵은골재 치환율 및 양생방법에 따른 콘크리트의 압축강도특성
전에스더(Jeon Esther),윤현도(Yun Hyun-Do),최기선(Choi Ki-Sun),유영찬(You Young-Chan),이세현(Lee Sea Hyun),이도헌(Lee Do-Heun) 대한건축학회 2007 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.27 No.1
Recycling demolished concrete as an alternative source of coarse aggregates for the production of new concrete can help solve the growing waste disposal crisis and the problem of depleted natural aggregates. However, to make such recycling feasible, the strength and durability of the recycled aggregate concrete must be assured. In this paper, fresh(air contents, slump) properties and the compressive strength of recycled aggregate concrete according to curing method are investigated experimentally. Concrete specimens were fabricated by ready-mix concrete and tested with different recycled coarse aggregate replacement level of 0%, 30%, 60% and 100%, respectively. For recycled coarse aggregate concrete, the change of air contents were bigger than natural coarse aggregate concrete. The air-cured/water cured strength ratio of recycled coarse aggregate concrete was 84.23~99.39%. Compressive strength of concrete with different recycled coarse aggregate replacement level was shown to be similar.
단일PE섬유를 혼입한 변형경화형 시멘트 복합체(SHCC)의 인장거동특성
전에스더(Jeon Esther),윤현도(Yun Hyun-Do),김윤수(Kim Yun-Su),장용헌(Jang Yong-Heon),유영찬(You Young-Chan),김긍환(Kim Keung-Hwan) 대한건축학회 2008 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.28 No.1(구조계)
Direct tensile response of strain hardening cement composites(SHCC) depends primarily on the material's tensile response, which is a water-cement ratio, direct function of fiber and matrix characteristics, the bond between them, and the fiber volume fraction. This paper discusses effect of water-cement ration and fiber volume fraction of the direct tensile response of SHCC with Polyethylene(PE) fiber. For these purposes, four kinds of PE fiber volumn fraction and two kinds of water-cement ratio were used: Vf :0.25%, 0.50%, 0.75%, 1.00%, W/C : 0.45, 0.60. For the same water-cement ratio, 45-PE1.00 specimen showed better overall behavior(Pseudo strain-hardening, Multiple cracking) than others. Tensile response of SHCC was necessarily correlated with compressive strength.
잔골재 입경에 따른 고인성 섬유보강 시멘트 복합체의 압축강도 특성
전에스더 ( Jeon Esther ),이원석 ( Lee Won-suk ),변장배 ( Byun Jang-bae ),윤현도 ( Yun Hyun-do ) 한국구조물진단유지관리공학회 2006 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.10 No.2
HPFRCC(High performance fiber reinforced cementitious composite) have made major advances in recent years, to the point where they are being adopted in building and bridge constructions. The most significant advantage of HPFRCC over conventional concrete is their high tensile ductility. But HPFRCC reduced economic efficiency due to silica sand and short fiber of expensiveness to exhibit strain-hardening accompanied by multiple cracking. This study is a part of series of researches to replace silica sand in HPFRCC to fine aggregate. The objective of this study was to investigate the compressive strength properties of HPFRCC according to fine aggregate size under cyclic loading for using fine aggregates as substitution of silica sand. As fine aggregate size are bigger, compressive strength and elastic modulus of PVA and PE HPFRCC were decreased under cyclic loading within the scope of this research.