• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 추계 학술논문 발표대회
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• pp.129-130
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• 2014

In the case of concrete structures which have been recently exposed to the marine environment, durability is greatly reduced by the freezing-thawing action. When it is used by appropriately replacing the ground granulated blast-furnace slag(GGBS) that is a industrial by-product, the concrete structure of marine environment is known to have a durability to freezing-thawing resistance. In this experiment, micropore in accordance with a replacement ratio of GGBS was confirmed to show different results respectively. The freeze-thaw resistance was showed different aspects respectively because it is different the amount of water in the pore due to the difference of micropore. Therefore, in this study, the freezing-thawing resistance of sea water by variation of micropores of slag concrete had been evaluated.

• Geomechanics and Engineering
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• 제19권4호
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• pp.361-368
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• 2019

This study aims to evaluate the applicability of a grout material that is mixed with carbon fiber, biogrout, ground granulated blast furnace slag (GGBS) powder and cement. Uniaxial compressive strength tests were performed on homo-gel samples at days of 1, 3, 7, 14 and 28. In addition, the variation of permeability with the mixing ratios was measured. Based on the uniaxial compressive strength test, it was confirmed that the uniaxial compressive strength increased by 1.2times when carbon fiber increased by 1%. In addition, as a result of the permeability test, it was found that when the GGBS increased by 20%, the permeability coefficient decreased by about 1.5times. Therefore, the developed grout material can be used as a cutoff grouting material in the field due to its strength and cut-off effect.

• 한국건설순환자원학회논문집
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• 제5권1호
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• pp.45-52
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• 2017

이 연구에서는 고로슬래그 다량 치환 콘크리트의 원전 콘크리트 적용을 위하여 기존 원전 콘크리트와의 내구성능 비교 및 분석을 수행하였다. 연구결과에 따르면 고로슬래그를 50% 치환한 콘크리트의 압축강도는 초기강도는 기존 원전 콘크리트보다 낮지만, 우수한 장기강도를 나타내었다. 반면, 기존 원전 콘크리트의 초기강도는 높았지만, 장기강도 발현율이 낮게 나타났다. 내구성능의 평가결과, 고로슬래그를 50% 치환한 콘크리트의 내구성능은 모든 평가항목에서 플라이애시 20% 치환 콘크리트와 비교하여 동등이상의 성능을 나타내었다. 특히. 저강도에서의 고로슬래그 50% 치환한 콘크리트는 염해 저항성과 탄산화 저항성, 동결융해 저항성의 향상효과가 뚜렷하게 나타났다. 반면, 감마선 조사에 따른 콘크리트 압축강도와 화학성분의 변화는 미미하게 나타났다.

• Structural Monitoring and Maintenance
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• 제2권1호
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• pp.35-48
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• 2015

The main objective of this study is to evaluate the long-term performance of various concrete composites in natural marine environment prevailing in the Gulf region. Durability assessment studies of such nature are usually carried out under aggressive environments that constitute seawater, chloride and sulfate laden soils and wind, and groundwater conditions. These studies are very vital for sustainable development of marine and off shore reinforced concrete structures of industrial design such as petroleum installations. First round of testing and evaluation, which is presented in this paper, were performed by standard tests under laboratory conditions. Laboratory results presented in this paper will be corroborated with test outcome of ongoing three years field exposure conditions. The field study will include different parameters of investigation for high performance concrete including corrosion inhibitors, type of reinforcement, natural and industrial pozzolanic additives, water to cement ratio, water type, cover thickness, curing conditions, and concrete coatings. Like the laboratory specimens, samples in the field will be monitored for corrosion induced deterioration signs and for any signs of failureover initial period ofthree years. In this paper, laboratory results pertaining to microsilica (SF), ground granulated blast furnace slag (GGBS), epoxy coated rebars and calcium nitrite corrosion inhibitor are very conclusive. Results affirmed that the supplementary cementing materials such as GGBS and SF significantly impacted and enhanced concrete resistivity to chloride ions penetration and hence decrease the corrosion activities on steel bars protected by such concretes. As for epoxy coated rebars applications under high chloride laden conditions, results showed great concern to integrity of the epoxy coating layer on the bar and its stability. On the other hand corrosion inhibiting admixtures such as calcium nitrite proved to be more effective when used in combination with the pozzolanic additives such as GGBS and microsilica.

• 한국건설순환자원학회논문집
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• 제5권4호
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• pp.488-495
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• 2017

본 연구에서는 열역학적 평형을 이용한 OPC의 재령에 따른 운동학적 수화 생성물 모델링과 GGBS의 치환률에 따른 수화 생성물의 변화를 모델링하였다. 열역학 데이터는 GEMS의 3rd party 데이터베이스, Cemdata18을 사용하였고, 시멘트 수화 모델링은 Parrot & Killoh 모델을 적용하였다. OPC모델링에서 재령에 따라 Pore solution의 이온 농도와 수화 생성물의 질량 및 부피 변화를 관찰할 수 있었다. GGBS모델링에서는 치환률이 증가함에 따라 장기강도를 지배하는 C-S-H의 생성량은 증가하지만, 내구성에 영향을 미치는 Portlandite의 생성량이 감소하여 탄산화에 대한 대책이 필요할 것으로 판단된다.

• 한국건축시공학회지
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• 제2권4호
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• pp.145-152
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• 2002

High fluid concrete unlike OPC concrete is made with various material, and the phase of fresh concrete is considerably different. In order to understand fluidity phase and mix properties of high fluid concrete, concrete is required to access as suspension structure which consists of aggregate and paste. The focus of this paper is to analyze the test results and quantify the effect of mix proportions of mortar and fineness modulus of sand on the properties of fresh mortar. The effect of water-binder ratio. sand-binder ration. contents of ggbs (by mass of total cementitious materials). and various contents of water reducing agent on the yield stress and plastic viscosity of the mix is studied. Based on the experimental results, the fellowing conclusions can be drawn: (1) The mixing time needed for high fluid mortar was approximately two times more than that of ordinary portland mortar. (2) The fluidity phase of mortar could be explained by yield stress of mix and the fluidity of mortar. (3) As the content of ggbs increased, yield stress of mortar was decreased and plastic viscosity of it was increased. (4) For the high fluid mortar, it was appeared that sand-binder ratio should be below 1.5.

• 한국건설순환자원학회논문집
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• 제3권2호
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• pp.115-121
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• 2015

본 연구에서는 $CO_2$ 배출 저감을 위한 저탄소 콘크리트 구조물 설계 절차를 제시하였다. 전과정 $CO_2$ 평가에 기반한 저탄소 콘크리트 구조물 설계 절차는 ISO 13315-2에서 요구하는 시스템 경계를 이용하였으며 구조물의 전과정 평가를 수행하기 위한 전과정 목록(life-cycle inventory, LCI)은 기본적으로 국가에서 구축한 LCI 데이터베이스 정보망을 이용하였다. 본 연구에서 제시한 절차에 따라 전단벽 콘크리트 구조물을 대상으로 전과정 $CO_2$ 평가에 대한 사례분석을 수행하였다. 기둥부재의 경우 GGBS 25% 치환 시 재료단계, 해체 및 파쇄단계, 운송단계에서 $CO_2$ 발생량 및 탄산화에 의한 $CO_2$ 포집량은 모두 감소하는 것으로 나타났으며 OPC 대비 약 26% 감소하는 것으로 나타났다. 기둥, 벽체, 보 및 슬래브 전체의 경우 GGBS 25% 치환에 따라 전과정 $CO_2$ 발생량이 약 22% 저감하는 것으로 나타났다.

• Advances in concrete construction
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• 제16권6호
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• pp.303-316
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• 2023

Using industrial wastes and construction and demolition (C&D) wastes is potentially advantageous for concrete production in terms of sustainability improvement. In this paper, a sustainable Self-Compacting Concrete (SCC) made with industrial wastes and C&D wastes was proposed by considerably replacing natural counterparts with recycled coarse aggregates (RCAs) and supplementary cementitious materials (SCMs) (i.e., Fly ash (FA), ground granulated blast furnace slag (GGBS) and silica fume (SF)). A total of 12 SCC mixes with various RCAs and different combination SCMs were prepared, which comprise binary, ternary and quaternary mixes. The mechanical properties in terms of compressive strength and static elasticity modulus of recycled aggregates (RA-SCC) mixes were determined and analyzed. Microstructural study was implemented to analyze the reason of improvement on mechanical properties. By means of life cycle assessment (LCA) method, the environmental impacts of RA-SCC with various RCAs and SCMs were quantified, analyzed and compared in the system boundary of "cradle-to-gate". In addition, the comparison of LCA results with respect to mechanical properties was conducted. The results demonstrate that the addition of proposed combination SCMs leads to significant improvement in mechanical properties of quaternary RA-SCC mixes with FA, GGBS and SF. Furthermore, quaternary RA-SCC mixes emit lowest environmental burdens without compromising mechanical properties. Thus, using the combination of FA, GGBS and SF as cement substitution to manufacture RA-SCC significantly improves the sustainability of SCC by minimizing the depletion of cement and non-renewable natural resources.

• 한국건축시공학회지
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• 제18권5호
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• pp.439-446
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• 2018

PHC파일은 깊은 관입량과 지지력 보강이 유리한 말뚝기초공법으로 사용량이 지속적으로 증가하고 있다. 일반적으로 PHC파일을 제조할 경우 압축강도의 증진을 위해 고강도 혼합재를 주로 사용하지만, 최근에는 경제성을 고려하여 고로슬래그 미분말을 활용하는 연구가 진행되고 있다. 이에 본 연구에서는 고강도 혼합재 대신 고로슬래그 미분말의 치환율 및 양생조건을 고려한 PHC파일을 제조한 후 공학적 특성에 대해 검토하였다. 실험 결과, 고로슬래그 미분말을 치환한 PHC파일은 50, $80^{\circ}C$ (Steam curing) 양생조건에 의해 압축강도가 증가하며, 특히 $80^{\circ}C$ (Steam curing) 양생조건에서 고로슬래그 미분말을 20% 치환한 PHC파일은 약 84MPa의 압축강도를 나타내었다. 또한, $20^{\circ}C$ (Room temperature curing)의 양생조건에 비해 $80^{\circ}C$ (Steam curing) 양생조건에서 더 많은 수화생성물이 발생하는 것을 확인할 수 있으며, 이 때문에 조직이 치밀해지고, 압축강도 증가에 영향을 준 것으로 판단된다.

• 센서학회지
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• 제25권4호
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• pp.275-279
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• 2016

Chemical vapor deposited (CVD) polycrystalline graphene is widely used for various sensor application because of its extremely large surface-to-volume ratio. The electrical properties of CVD-graphene is significantly affected by the grain size and boundaries (GGBs), but evaluation of GGB of continuous monolayer graphene is difficult. Although several evaluation methods such as tunneling electron microscopy, confocal Raman, UV/ozone-oxidation are typically used, they still have issues in evaluation efficiency and accuracy. In this paper, we suggest an improved evaluation method for precise and simple GGB evaluation which is based on UV/ozone-oxidation and chemical etching process. Using this method, we could observe clear GGBs of CVD-graphene layers grown by different process conditions and statistically evaluate average grain sizes varying from $1.69{\sim}4.43{\mu}m$. This evaluation method can be used for analyzing the correlation between the electrical properties and grain size of CVD-graphene, which is essential for the development of graphene-based sensor devices.