• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.275-282
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• 2002

High fluidity concrete needs high dosage of superplasticizer to acquire sufficient fluidity and high contents of fine powder and viscosity agents to prevent segregation. But it requires high manufacturing cost and has difficult in quality control. Therefore, in this paper, determination of optimal mixture proportion of segregation type superplasticizer for high fluidity concrete and manufacturing high fluidity concrete by applying developed segregation reducing type superplasticizer are discussed using flowing concrete method. According to test results, as dosage of superplasticizer increases, it shows that fluidity and bleeding increase, while air contents and ratio of segregation resistance decrease. It also shows that adding viscosity agent into it reduce bleeding and improve segregation resistance. Dosage of AE agent into it containing viscosity agent recovers loss of air contents during flowing procedure. Combination of proper contents of superplasticizer, viscosity agent and AE agent make possible to develope segregation reducing type superplasticizer Compressive strength of high fluidity concrete applying flowing method with it is higher than that of base concrete. No differences of compressive strength between compacting methods are found.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.101-106
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• 2009

We study on the segregation reduction effect of Self-Leveling Color Mortar by using variable composition set of plasticizer and thickener, Naphthalene, melamine and polycarbonate-based dispersants were employed as plasticizers for examining on fluidity of mortar mixtures. For enhancement of mortar stability without loss of it's fluidity, two types of thickener were used such as polysaccharide(PS) and hydroxyethylcellulose(HEC). As a result, the most effective mortar was composed by feeding 0.519% of polycarbonate-based dispersant with 0.002587% of PS and 0.155844% of HEC on amount of basic mortar.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.3
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• pp.57-62
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• 2020

Among the sewage pipes installed in Korea, the length of concrete pipes exceeding 20 years is 66,334 km (42.5%). Deteriorated concrete sewer pipes need to be repaired due to the leakage of internal sewage, which causes problems such as sink holes by expanding the cavity around the pipeline. In this study, we tried to apply anti-washout underwater mortar with ultra rapid hardening cement and segregation reducing agent to sewage pipe repair. As a result of the setting time test, the final set time was delayed by up to 172% by incorporating segregation reducing agent. In the test for measuring the degree of mortar segregation in water, it was measured at pH 12 or less under all mixing conditions. In addition, the suspension amount was measured to be 50 mg / l or less to satisfy the KCI-AD102 standard by incorporating a segregation reducing agent. In terms of the average value of mortar compressive strength, by incorporating segregation reducing agent, the strength of the specimens produced in air was more than 80% of that of the specimens produced in water. Conversely, the bond strengths of the specimens produced in water were measured to be higher than those of the specimens produced in air. Water resistance was evaluated by measuring water absorption and water permeability. Water absorption and water permeability were reduced by 42.6% and 36.6%, respectively, by mixing segregation reducing agent.

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.217-224
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• 2003

It is necessary to reduce bleeding, which is a kind of segregation of fresh concrete, for improvement of quality of concrete structure. But, besides using high qualify material and adjusting mixture ratio, there is no easy solution to reduce bleeding by now. For that reason, this study is intended to develop bleeding reduction agent and to investigate its application. The test results are following. At first, recommended mixture ratio of bleeding reduction agent is proven to be MC viscosity agent : defoaming agent : superplasticyzer of 1 : 0.004 : 0.2. It goes to prove that bleeding reduction agent does not have bad effect on the quality of concrete such as fluidity, air content and the strength of hardened concrete etc, and can reduce bleeding effectively. Therefore it is thought that bleeding reduction agent can be applied to construction field effectively.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.288-290
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• 2005

고분자전해질 연료전지는 자동차, 분산전원 및 이동전원 등에 대한 차세대 에너지원으로 채택 가능성이 높아지고 있다. 고분자전해질 연료전지 시스템의 상용화를 위한 가장 큰 걸림돌 중 한 가지로 가격문제를 들 수 있는데, 연료전지 스택이 전체 가격의 약 $50\%$를 차지하고 있다. 또한 스택을 구성하는 요소 중 분리판의 가격 비중은 약 $30\%$를 차지하고 있어, 분리판의 생산단가 저감은 연료전지의 상용화를 위해 반드시 해결해야 될 문제이다. 본 연구에서는 탄소를 재료로 하는 분리판에 대한 연구를 수행하였으며, 압축성형방식으로 제작된 다양한 복합재료 분리판 및 흑연 분리판에 대한 기계적 강도, 물리적 특성, 화학적 안정성을 조사하였으며, 가흑 운전 시 분리판내에 함유되어있는 고분자 성분의 침출에 의한 연료전지의 성능변화가 발생하는지 확인하였으며 이에 대한 단위전지의 성능평가를 수행하였다. 이러한 결과를 토대로 최적의 압축성형 복합체 분리판 제작 방향을 제시하고, 보다 신뢰성 있는 분리판 성능평가 기준을 확립하고자 하였다.

• Journal of the Korea Concrete Institute
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• v.13 no.4
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• pp.336-345
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• 2001

The construction of underwater structures has been increased, but underwater concrete hassome problems of quality deterioration and contamination around in-situ of civil and architecture; therefore, new materials and methods for them are demanded. In this paper in-situ application of underwater antiwashout concrete which is manufactured for trio purpose of not only decreasing suspended solids and the heat of hydration but also increasing long term strength was studied. In the case of mock-up test(Ⅰ), when underwater antiwashout concrete, whose slump flow was 58 cm, was placed in the mock-up test at a speed of 24 ㎥/hr, it took about a minute to flow to the side wall, and the surface was maintained at horizontal level. In this case, compressive strength of the core specimens in each section was higher than the standard design compressive strength of 240 kgf/㎠. In the case of mock-up test(II), pH value and suspended solids of high strength underwater antiwashout concrete were 10.0∼11.0 and 51 mg/ℓ at 30 minutes later, initial and final setting time were about 30, 37 hr, and the slump flow of that was 53$\pm$2 cm. In the placement at a speed of 27 ㎥/hr, there was no large difference in flowing velocity, with or without reinforcement and flowing slope was maintained at horizontal level. In this case, compressive strength and elastic modulus of the core specimens somewhat decreased as flowing distance was far : however, those of central area showed the highest value.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.281-289
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• 1998

This study has been performed to test the flowability and filling ability of high flowing concrete as well as distribution of aggregate and pore of core specimen, heat of hydration, compressive strength and core strength of concrete. In addition, the resistance to chloride ion penetration and chemical solutionof concrete was tested in order to evaluate the resistance to sea water of concrete and its application of high flowing concrete using blended low heat cement in the field of Seohae Grand Bridge. The properties of high flowing concrete with blended low heat cement were compared with ordinary 25-240-15 concrete using Type V cement. As the results of this study, the flowability and filling ability of high flowing concrete with blended low heat cement is satisfied without vibration. Though the cement content of high flowing concrete with blended low heat cement was 400kg/m$^2$, the rising temperature of it was relatively lower than that of the ordinary 25-240-15 concrete with Type V cement. Also, the compressive of high flowing concrete with blended low heat cement is similar to that of the ordinary 25-240-15 concrete with Type V cement.

• Journal of the Korea Institute of Building Construction
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• v.17 no.5
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• pp.429-435
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• 2017

The aim of the research is, for normal strength range concrete mixture, to evaluate the fluidity development and robustness of the mixture depending on various water reducers. Although a usage of water reducer has been essential to make a concrete under the current conditions of worsen aggregate quality, selection of appropriate performance of water reducer is significant. Hence, in this research, regarding the normal strength range mortar, three different performance of water reducers were evaluated in aspects of securing fluidity, and robustness, rheological behaviors. Additionally, for the concrete mixture, the fluidity change was evaluated depending on unit water content for each different water reducer, and the water reducing performance with manufacturing cost was compared and analyzed. By the result of this research, it is expected to provide a case of determining appropriate kind of water reducer and to contribute on conditions of securing sufficient fluidity with stable quality and economical advantage.

• The Korean Journal of Mycology
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• v.43 no.4
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• pp.247-252
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• 2015

Aronia (Black chokeberry, Aronia melanocarpa) belonging to the Rosaceae family, is native to eastern North America. Aronia contain high levels of flavonoids, mostly anthocyanins and proanthocyanidins, which are known as condensed tannins. The dominant proanthocyanidins in aronia are (-)-epicatechin and (+)-catechin. The concentration of proanthocyanidins in aronia is higher than in other berries, however due to the astringent taste it is not desirable for consumption. Therefore, the purpose of this study is to evaluate the effect of aronia on the reduction in tannins by yeast isolated from regional Jeotgal. We isolated strains of yeast with high ${\beta}$-glucosidase activity from Jeotgal, with the MTY2 strains exhibiting a reduction in final tannin concentration according to thin layer chromatography (TLC) analysis. MTY2 was confirmed as Kazachstania servazzii using an 18S rDNA sequence and named as K. servazzii MTY2. K. servazzii MTY2 showed most significant growth when K. servazzii MTY2 was cultured in a solution of 10% (w/v) glucose, 3% (w/v) tryptone and 0.1% (w/v) sodium chloride. According to the high performance liquid chromatography (HPLC) analysis, the (+) - catechin peak is present, but (-) - epicatechin peak was reduced at culture condition added with 10% glucose in medium.

• Cement
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• s.189
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• pp.41-48
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• 2011

고로시멘트는 포틀랜드시멘트와 고로슬래그의 혼합시멘트로, 최근에는 특히 저탄소 녹색성장 환경에 우수한 시멘트로서 관심이 모아지고 있다. 1824년 영국의 연와공 조셉 아스프딘(Joseph Aspdin)에 의해 발명된 포틀랜드시멘트는 약 184년의 역사를 가지고 있는 반면에, 일본의 슬래그시멘트 역사는 작년이 탄생부터 정확히 100년이 되기 때문에, 잠시 그 역사의 일부를 돌이켜 생각해 보고자 한다. 최근 슬래그시멘트는 건설시장에서 보통포틀랜드시멘트와 경쟁하기 위하여 발열억제를 위한 저발열고로시멘트를 개발하고, 강도경쟁에 의한 품질안정을 위하여 분리분쇄 추진, 고로슬래그에 적합한 클링커를 개발하고, 자기 수축 저감 등을 위한 연구도 병행하고 있다. 날로 심화되는 건설환경에서 살아 남기 위한 여러 방법들이 강구되고 있는 것이다. 고로시멘트는 보통포틀랜드시멘트와 비교해서 중성화, 강도발현을 위한 충분한 습윤양생 등 몇 가지 약점도 있지만, 슬래그시멘트 본연의 고유의 특성을 잘 나타내는 내해수성, 내염성, ASR 등의 장점들도 않고 "환경에 뛰어난" 시멘트로 각인된 만큼, 갖고 있는 특징들을 충분히 잘 활용하고, 개선 보완 시켜나가면 21세기의 최상의 재료로 평가 받을 수 있다고 기대해 본다. 끝으로, 본 자료는 신일철고로시멘트(주)단(檀)이 기고한 (콘크리트공학 2010년 10월호) 논문을 요약 발췌한 것이다.