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해양환경을 고려한 플라이애쉬${\cdot}$수중 불분리 콘크리트의 압축강도에 관한 실험적 연구
권중현,정희효,문제길,Kwon, Joong-Hyen,Jung, Hee-Hyo,Moon, Je-Kil 한국콘크리트학회 1999 콘크리트학회지 Vol.11 No.2
바다에 콘크리트를 타설 할 때는 육상과는 달리 여러 가지 제약을 받게 되며 타설 후에는 해양의 물리, 화학작용과 혹독한 기상작용을 받게 된다. 해양환경에서 내구적인 고품질의 콘크리트를 제조하기 위해 플라이애쉬를 혼입한 수중 불분리 콘크리트를 해수 중에 타설${\cdot}$양생한 후 압축강도를 측정하고 기중 및 담수 중에서 양생한 것과 비교하여 그 특성을 구명하였다. 우리 나라 연안의 87년에서 96년까지 10년간 수심 10m에서 20m의 연 평균수온이 14.9$^{\circ}C$ 임을 고려하여, 수온을 $15{\pm}3^{\circ}C$로 조절할 해수 중에 타설${\cdot}$양생한 후 콘크리트의 압축강도를 측정하여 플라이애쉬 사용효과를 확인하였다. 시험결과 해수 중에서 플라이애쉬를 사용하지 않은 불분리 콘크리트의 경우 재령 91일부터 1년까지의 강도증가는 2%에 머무나 플라이애쉬를 단위 결합재 중량비로 10%에서 50%까지 10%씩 증가시켜 치환한 결과 압축강도는 각각 15%, 19%, 24%, 51%, 64%가 증가되었다. 플라이애쉬의 적정 사용량은 콘크리트의 조기강도가 요구되는 구조물의 경우 단위 결합재에 대한 중량비로 10%정도 치환함이 적절하며, 내구성과 경제성을 고려한다면 40%~50%정도가 효과적임을 알 수 있었다. When the concrete is cast at the sea, there are lots of restrictions in the working process being different from in land, and the concrete is suffered from the physical and chemical action in terms of marine environment. The compressive strength was measured after antiwash out underwater concrete mixed with fly ash had been cast and cured in order to produce the endurable high performance concrete, and then its characteristic was discussed by comparing one cured in air with in fresh water, and the effect of fly ash usage under the properly controled sea water temperature of $15{\pm}3^{\circ}C$ was also covered. The present work showed that the proper usage of fly ash was obtained at the condition of around 10% of substituted binder weight under the structure required the early age strength, and at the condition of over 40% if considering its durability and economy.
플라이애시 수중불분리성 콘크리트의 수밀성에 관한 실험적 연구
권중현(JUNG-HYUN KWON),김봉익(BONG-IK KIM) 한국해양공학회 2008 韓國海洋工學會誌 Vol.22 No.4
This paper describes the effects of fly ash replacement on the water tightness of antiwashout underwater concrete, which replaced the cement with fly ash from 0% to 30%. The experimental work was performed to find out the depth of permeation of concrete specimens cast in air and cured in 23℃ tap water using an open center pressure type of water permeation tester. The results showed that the permeation depth values of antiwashout underwater concrete were deeper than normal concrete, but that an admixture using fly ash during antiwashout underwater concrete casting in air made it more watertight than normal concrete according to the water permeation testing. SEM observations of the specimensof fly ash antiwashout underwater concrete showed that it wasmore packed with structures because of the pozzolan reaction of the fly ash and cement.
플라이애쉬를 사용한 수중불분리성 콘크리트의 응결에 관한 실험적 연구
권중현(JUNG-HYUN KWON),김봉익(BONG-IK KIM) 한국해양공학회 2001 韓國海洋工學會誌 Vol.15 No.4
This paper describes the effect of fly ash replacement on the setting time of antiwashout underwater concrete, where cement was replaced by 0% to 50%. Experimental work was performed on the condition of sea water and in air to find out the characteristics of setting time between the concretes that were cast in air and cast in 15℃ of sea water. The experimental results show that the setting time of underwater concrete with 50% replacement was delayed about 10 hours than normal concrete. And it can be concluded that, at the case of underseawater concrete addicted with fly ash the delayed final setting times are shown as the function Tf=0.069F+7.69, where Tf is the delayed final setting time and F is quantity of fly ash respectively. These results confirm that the setting time of underseawater concrete could be prolonged.
Fly Ash를 사용한 수중불분리 콘크리트의 유동성에 관한 연구
권중현(Joong-Hyen Kwon),배기성(Ki-Seong Bae) 한국해양공학회 1998 韓國海洋工學會誌 Vol.12 No.1
This paper is to investigate the Fluidity of Antiwashout Underwater Concrete containing Fly Ash. The results of study are concluded as follows : the increase in Slump Flow value did not happen in the plain concrete which was replaced cement by Fly Ash ; however, the maximum value could reach in the replacement of 30% of Fly Ash by weight of cement in the Fly Ash replaced concrete. On the condition of Fly Ash-Antiwashout Underwater Concrete in expecting 50㎝ of the Slump Flow, it was necessary that the usage amount of Superplasticizer be around 1% of unit Binder, and 1.5% in 60㎝ of the Slump Flow, respectively.
플라이애쉬를 사용한 수중불분리성 콘크리트의 수화열에 관한 연구
권중현(JUNG-HYUN KWON) 한국해양공학회 2000 韓國海洋工學會誌 Vol.14 No.4
The concretes cast in the sea water would be likely to be rich mix and mass concrete. Therefore it is important to check out the hydration heat of concrete and to reduce it to prevent the concrete from processing the temperature crack. Recently the antiwashout agent is used on underwater concretes for preventing from the segregation of concrete in the water. The experimental studies were done for the combined cement replaced by fly ash 30% unit weight of binder to study on the characteristics of hydration heat of antiwashout underwater concrete, and its characteristic was discussed by comparing one cast in sea water with another one in air. The present paper showed that the hydration heat of concrete replaced by 30% of fly ash was more significantly reduced than the normal concrete. The hydration heat of antiwashout underwater concrete was higher than that of normal concrete, but it was reduced lower than the normal concrete by adding fly ash.
플라이애쉬 수중불분리성 콘크리트의 내해수성에 관한 염화물 촉진 시험
권중현(JUNG-HYUN KWON),김봉익(BONG-IK KIM) 한국해양공학회 2005 韓國海洋工學會誌 Vol.19 No.6
This paper describes the effect of fly ash replacement on seawater resistance of anti-washout underwater concrete, which was replaced cement by fly ash from 0% to 50%. The experimental work was performed to find out the variations of length and weight of specimens, using a chloride acceleration test in 40℃ The results show that the admixture using fly ash on an anti-washout underwater concrete in the sea environment makes it more durable for the attacks of chloride by seawater. Also, the length of specimens of anti-washout underwater concrete, at age 180 days, increased substantially, compared with normal concrete; however, the mixture in which cement was replaced 50% of fly ash shows 93% reduction of the expansion, compared with the normal anti-washout underwater concrete specimen.
플라이애시를 혼입한 수중불분리성 콘크리트의 내 황산염에 관한 실험적 연구
권중현(Joong-Hyen Kwon),김봉익(Bong-Ik Kim) 한국해양공학회 2011 韓國海洋工學會誌 Vol.25 No.3
This paper describes the effects of fly ash replacement on the sulfate resistance of antiwashout underwater concrete which was replaced cement by fly ash from 0% to 50%. and the experimental works were performed on sulfate acceleration test of 5%Na₂SO₄ solution to find out the variance of length and weight if specimens. The experimental result shows that the length if specimens of antiwashout underwater concrete age at 180day was highly increased compare with normal concrete by acceleration test. but the mixture which was replaced 50% of fly ash shows reduction if the expansion, weight various, compare with normal concrete specimen. accordingly by using fly ash as admixture in antiwashout underwater concrete in sea environment, it will makes more durable for the attacks of sulfate by sea water.
하모니 서치 알고리즘과 고유진동수 제약조건에 의한 트러스의 단면과 형상 최적설계
김봉익(Bong-Ik Kim),권중현(Jung-Hyun Kwon) 한국해양공학회 2013 韓國海洋工學會誌 Vol.27 No.5
We present the optimum design for the cross-sectional(sizing) and shape optimization of truss structures natural frequency constraints. The optimum design method used in this paper employs continuous design variables and the Harmony Search Algorithm(HSA). HSA is a meta-heuristic search method for global optimization problems. In this paper, HSA uses the method of random number selection in an update process, along with penalty parameters, to construct the initial harmony memory in order to improve the fitness in the initial and update processes. In examples, 10-bar and 72-bar trusses are optimized for sizing and 37-bar bridge type truss and 52-bar(like dome) for sizing and shape. Four typical truss optimization examples are employed to demonstrate the availability of HSA for finding the minimum weight optimum truss with multiple natural frequency constraints.