• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.136-145
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• 1997

The purpose of this study is to develope of alternative adimixture for manufacture of PHC pile(compressive strength above 800kg/$\textrm{cm}^2$). For the investigation, properties of alternative admixture admixed with II-anhydrite and pozollanic fine powders(e.q., Fly-ash, Silica-Fume), the fluidity and viscosity in the cement pastes, the fluidity and compressive strength in mortars at steam curing condition, were respectively examined. Also, properties of compressive strength of concretes with exiting admixture(specimen name SM) and alterantive admixture(specimen name AP) for PHC pile, at steam and standard curing condition, were compared each other. As a result of this experimental study, it was found that specimens admixed with II-anhydrite and pozollanic fine powders had an increase on the fluidity of cement paste and mortar, and compressive strength of mortar and concrete was as good as concrete with SM.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.773-776
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• 2006

This experimental study is the fundamental report to use the ternary concrete. This study performed to know physical properties of ternary concrete according to replacement ratio of pozzolanic admixtures and curing temperature conjugation. To investigate Strength development properties of according to replacement ratio of pozzolanic admixtures, both fly ash replaced on portland cement in 5, 10 and 15% weight ratios and blast furnace slag replaced on the portland cement in 5, 15, 20, 30 and 40% weigt ratios was used. Also this is studied fresh and hardened concrete properties in condition of curing temperature $10^{\circ}C\;and\;20^{\circ}C$. The followings are the summary of which concluded in this study. Considering the concrete cured over 28 days compressive strength, most replacement ratios of pozzolanic admixtures were higher than plain concrete that. Compressive strength development properties of ternary concrete according to curing temperature conjugation were similar except for early age.

• 콘크리트학회논문집
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• 제18권6호
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• pp.759-767
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• 2006

본 연구에서는 등가재령개념에 의한 적산온도방법을 이용하여 플라이애쉬를 사용한 초지연 콘크리트의 응결시간 예측방법을 제시하였다. 플라이애쉬 치환 및 초지연제 혼입률 변화에 따른 양생온도별 응결시간은 초지연제 혼입률이 증가하고, 양생온도가 낮을수록 지연되는 것으로 나타났다. 또한 Arrhenius의 함수에 의한 겉보기 활성화 에너지는 배합별로 약간의 차이는 존재하지만 $24{\sim}35KJ/mol$의 범위로 나타났는데, 이는 일반적인 조건에서의 겉보기 활성화 에너지값의 범위인 $30{\sim}50KJ/mol$ 보다 작은 값으로 나타났다. 플라이애쉬 치환율 및 초지연제 혼입률별 겉보기 활성화 에너지를 등가재령식에 대입한 결과 양생온도별로 거의 유사한 값으로 나타나, 응결시간 예측에 등가재령에 의한 적산온도 방법이 효과적으로 적용될 수 있을 것으로 판단되었다. 아울러 등가재령 및 플라이애쉬 치환율 변화에 따른 초지연제 혼입량 추정에 관한 다중상관 회귀 모델을 제안하여 응결시간 및 초지연제 첨가량을 결정할 수 있도록 하였고 회귀 모델에 의한 해석 예측치와 실측치 간에 매우 양호한 상관성을 갖는 것으로 나타났다. 따라서 본 연구에서 제안된 초지연제 혼입률 및 플라이애쉬 치환율별 응결시간 예측 모델은 실무현장에서 초기재령 콘크리트의 응결 시간 평가에 보다 합리적인 품질관리 방법으로 활용이 가능할 것으로 판단된다.

• 한국건축시공학회지
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• 제12권2호
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• pp.161-168
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• 2012

본 연구는 지반매립재 용도를 대상으로 무 시멘트 상태에서, RA 사용 FA 모르타르의 특성에 미치는 RP 치환율의 영향을 검토하였는데, 그 결과를 요약하면 다음과 같다. 먼저, W/B 및 공기량은 RP 치환율이 증가할수록 증가하는 경향을 나타내었다. 압축강도는 재령 14일 이전 초기 재령에서는 강도가 거의 발휘되지 못하였으나, 재령 14일을 기점으로 28일에 이르러서는 약 1.5~2.0 MPa 정도의 강도 값을 나타내었다. 양생온도 $20^{\circ}C$의 경우 RP 치환율 100 %를 제외한 모든 수준에서 순수 FA에 비해 RP 치환율이 증가할수록 강도는 증가하였는데, RP 25 %에서 최고 강도값을 나타내었다. 양생온도 $35^{\circ}C$에서는 $20^{\circ}C$보다 RP 치환율이 작을수록 온도의존성이 큰 것으로 나타났다. 한편, SEM분석결과, 순수 FA에서도 일정 재령이 경과하면 RA의 알칼리 자극으로 포졸란 반응이 생성되어 조직이 치밀화됨을 확인할 수 있었고, RP 치환율 25 %일 때 RP의 미수화 시멘트 입자의 수화 및 FA의 포졸란 반응으로 수화물이 가장 밀실하게 생성되었다.

• 한국건축시공학회지
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• 제13권6호
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• pp.513-521
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• 2013

This study aimed to examine whether heat curing methods of concrete subjected to $-10^{\circ}C$ could be effective by varying the combination of heating cable and surface heat insulations. Three different concrete specimens incorporating 30% fly ash with 50% W/B were fabricated to simulate wall, column and slab members with dimensions of $1600{\times}800{\times}200$ mm for slab, $800{\times}600{\times}200$ mm for wall and $800{\times}800{\times}800$ mm for column. For heat curing combinations, Type-1 specimens applied PE film for slab, plywood for wall and column curing. Type-2 specimens applied double layer bubble sheet (2LB) and heating coil for slab, and 50 mm styrofoam for wall and column curing. Type-3 specimen applied 2LB for slab, electrical heating mat for wall and column inside heating enclosure. The test results revealed that the temperature of Type 1 specimen dropped below $0^{\circ}C$ beginning at 48 hours after placement due to its poor heat insulating capability. Type 2 and 3 specimens maintained a temperature of around $5{\sim}10^{\circ}C$ after placement due to favorable heat insulating and thermal resistance.

• 콘크리트학회논문집
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• 제12권6호
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• pp.23-34
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• 2000

This paper reports the effects of curing temperature and aging on the strength and the modulus of elasticity. In oder to determine the strength and the modulus of elasticity with curing temperature and aging, experimental and analytical methods are adopted. The tests of 480 cylinders are carried out for type I, V and V with 15 percent replacement of fly ash cement concretes, which are cured at isothermal conditions of 10, 23, 35 and 5$0^{\circ}C$. and the concrete cylinders are tested at the ages of 1, 3, 7 and 28 days. According to the experimental results, the concrete subjected to high temperature at early ages attaines higher early-age compressive and splitting tensile strength but eventually attaines lower later-age compressive and splitting tensile strength. Even if modulus of elasticity has the same tendency, the variation of modulus of elasticity with curing temperature is smaller than that of compressive strength. Based on these experimental results, the relationships among compressive strength, modulus of elasticity and splitting tensile strength are proposed considering the effects of curing temperature, aging and cement type.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 추계 학술논문 발표대회
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• pp.23-24
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• 2014

Currently, cement and concrete industries have been contributing to the CO₂ emission worldwide. Because of that, the efforts to minimize CO₂ have been the subject of many researches. This study focus on the use of GGBFS and fly ash in mortar specimens as a patial replacement of cement. Because of the limitation of the initial compressive strength, the newly efforts to enhance the strength through CO₂ Curing was adapted. To accelerate the reaction with CO₂, MgO was replaced by percentage from 0 to 100%. Results showed that compressive strength values at 7 days with CO₂ curing done on specimens was higher than that with no CO₂ curing. Similar trend was observed at 14 days too. It is therefore appeared that CO₂ curing has an obvious effect on compressive strength development of mortar specimens.

• 한국환경과학회지
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• 제19권5호
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• pp.639-646
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• 2010

Differently from fly ash, the bottom ash produced from incinerated urban solid waste has been treated as an industrial waste matter, and almost reclaimed a tract form the sea. If this waste material is applicable to foam concrete as an fine aggregate, however, it may be worthy of environmental preservation by recycling of waste material as well as reducing self-weight of high-rising structure and long-span bridge. This research has an objective of evaluating the effects of application of bottom ash on the mechanical properties of foam concrete. Thus, the ratio of bottom ash to cement was selected as a variable for experiment and the effect was tested by compression strength, flexural strength, absorption ratio, density, expansion factor. It can be observed from experiments that the application ratios have different effects on the material parameters considered in this experiment, thus major relationship between application ratio and each material parameter were finally introduced. The result of this study can be applied to decide a optimal mix design proportion of foam light-weight concrete while bottom ash is used as an fine aggregate of the concrete.

• 한국농공학회지
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• 제16권3호
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• pp.3472-3476
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• 1974

This test was attempted to investigate the effects of some mix designs of concreteon the compressive strengths and corrosive rates when exposed to sea water of the West Sea. In this test, concrete mixes consisted of an ordinary concrete, a pozzolan concrete and concretes with different admixtures such as fly ash, pozzolith and vinsol resin. Compressive strengths of the concrete were measured at ages of 1-year and 2-years when exposed to both sea water and fresh water. Corrosive rate was tested at ages of 1-year and 2-years when exposed to sea water only. The results obtained from the test may be summarized as follows: (1) When all of concretes were exposed to fresh water, compressive strength of an ordinary concrete was the lowest at all mixes of concretes, and all of them showed higher strength as the exposing age is longer. It was evidance that the uses of pozsolan cement, fly ash, pozzolith and vinsol resin in mix design of concrete had an effect on increasing compressive strength and that fresh water also had an effect on curing concretes even though at a long-time age. (2) When concretes were exposed sea water, a concrete with fly ash was the highest in compressive strength and its strength was increasing as the exposing age is longer, but the other concretes were decreased at 2-year exposure. It was found that a concrete with fly ash was the most effective on compressive strength of all concrete, but the other concretes were attacked by action of the sea water. (3) The use of vinsol resin admixture was the most resistant to corrosion by sea water, while the use of pozzolith was the most serious at corrosion and the others were corroded to almost same extent. (4) The relationship between corrosions and compressive strengths of concretes was not clearly correlated yet. It was known that the corrosive rate of concretes could not affect to compressive strengths by 2-year exposure of the sea water. (5) Pozzolan concrete was the most effective in compressive strength when exposed to fresh water only, However, the use of a fly ash admixture was available for compressive strength when exposing to both fresh water and sea water. It was also noticed that the use of vinsol resin was not available for strengths of concrete but for resistance to corrosion when exposed to sea water. (6) It was found that the use of pozzolith was so defective in compressive strengths and corrosiive resistance when exposing to sea water that it was only available for fresh water.

• 콘크리트학회논문집
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• 제21권4호
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• pp.449-455
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• 2009

최근 각종 산업화에 따른 탄산가스 배출량의 증가는 철근콘크리트구조물의 탄산화를 촉진시켜 구조물의 내 구성을 저하시키고 있다. 이미 선진 각국에서는 탄산가스 증가량을 고려하여 철근콘크리트구조물의 탄산화에 관한 안 전 관리 대책을 마련하고 있지만 현재까지도 실 구조물의 탄산화를 정확하게 예측하기 어렵고 탄산화 측정하기 위해서 는 많은 시간과 노력이 소요된다. 최근에 개발된 급속 촉진 탄산화 시험은 대기 중 $CO_2$농도를 100%로 하여 보다 신속 하게 탄산화 시험 결과를 제공할 수 있다. 본 논문에서는 플라이애쉬 콘크리트의 탄산화 특성을 알아보기 위하여 기존 에 주로 사용된 촉진 탄산화 시험과 급속 촉진 탄산화 시험에 의한 탄산화 결과를 비교, 분석하였다. 또한 장기재령에 서 플라이애쉬 콘크리트의 탄산화 특성을 알아보기 위하여 급속 촉진 탄산화 시험을 이용하여 재령 180일의 콘크리트 시편의 탄산화 실험을 수행하였다. 그 결과 플라이애쉬 콘크리트는 초기재령에서 탄산화에 다소 취약하였지만, 장기재 령에서는 OPC에 비하여 탄산화 저항성이 향상됨을 알 수 있었다.