• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표회 논문집(I)
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• pp.93-98
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• 1998

Fluidity retention of concrete used high range water reducing AE agent(HWAE) is varied according to type, dosage amount and dosing method of HWAE. The type and substitution ratio of mineral admixture also have influence on the fluidity retention of concrete using HWAE. For the purpose of improving the fluidity retention in concrete used HWAE, 3 types of HWAE and ground granulated blast furnace slag(SG) are applied in cement-based composites such as cement paste, mortar and concrete respectively. According to using the HWAE of naphthalene sulfonates and SG, the fluidity retention of mortar and concerete is improving the fluidity retention and strength of concrete regardless of type of HWAE.

• 콘크리트학회지
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• 제10권6호
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• pp.313-323
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• 1998

고성능 AE감수제를 사용한 콘크리트의 유동성 유지성능은 고성능 AE감수제의 주성분 및 사용량, 사용방법과 광물질 혼화재의 종류 및 혼합률 등에 따라서 영향을 받는다. 본 연구에서는 주성분이 다른 3종류의 고성능 AE감수제의 사용량과 사용방법을 변화시키고 분말도가 다른 3종류의 고로슬래그 미분말을 활용하여 시멘트풀, 모르터 및 콘크리트의 유동성 유지성능과 강도특성을 비교고찰하여 효율적인 유동성 유지방안을 제시하고자 하였다. 연구결과 고성능AE감수제를 사용한 콘크리트의 유동성 유지성능은 경과시간에 따른 시멘트 입자의 응집성과 밀접한 상관성이 있으며 나프탈린계 고성능 AE감수제의 사용과 고로슬래그 미분말의 분말도가 작고 혼합률이 클수록 모르터 및 콘크리트의유동성 유지성능이 현저히 향상되었다. 한편 고성능AE감수제의 종류에 관계없이 30분후 첨가방법이 유동성 유지성능 및 강도향상에 있어서 일석이조의 좋은 성과가 있었다.

• 콘크리트학회논문집
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• 제12권2호
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• pp.99-107
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• 2000

This research investigates experimentally an effect on the properties of the high flowing concrete to be poured in the under-ground slurry wall of Inchon LNG receiving terminal(#213,214-TK) according to variations of concrete materials. Variables for sensitivity test were selected items as followings. 1) Concrete temperature (3cases), 2) Unit water (5cases), 3) Fineness modulus of fine aggregate (5cases), 4) Particle size of lime stone powder (3cases), 5) Replacement ratio of blast-furnace slag (4cases) and 6) Addition ratio of high range water reducing agent (5cases). And fresh conditions of the super flowing concrete should be satisfied with required range including slump flow(65$\pm$5cm), 50cm reaching time of flow(4~10sec), V-lot flowing time(10~ 20sec), U-box height(min. 300mm) and air content(4$\pm$1%). As results for sensitivity test, considered flow-ability, self-compaction and segregation resistance of the high flowing concrete, material variations and conditions of fresh concrete should be satisfied with the range as follwings. 1) Concrete temperature are 10~2$0^{\circ}C$(below 3$0^{\circ}C$), 2) Surface moisture of fine aggregate is within $\pm$ 0.6%, 3) Fineness modulus of fine aggregate is 2.6$\pm$0.2, 4)Replacement ratio of blast-furnace slag is 45~50% and 5) Addition ratio of high range water reducing agent is within 1%. Based on the specification for quality control, we successfully finished concrete pouring on the under-ground slurry wall having 75,000㎥(#213,214-TK) and accumulated real date in site.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.811-815
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• 2003

The effects of high-range water-reducing agent (WRA) content and polymer-cement ratio on the strength properties of autoclaved SBR-modified mortars with WRA are examined. As a result, the flexural strength of the autoclaved SBR-modified mortars with WRAs tends to increase with increasing WRA content and polymer-cement ratio, and reaches a maximum at a WRA content of 2.0%. The compressive strength of the autoclaved SBR-modified mortars with WRAs is inclined to increase with increasing WRA content and polymer-cement ratio, and reaches a maximum at a WRA content of 2.0% and a polymer-cement ratio of 10%. From the test results, the addition of the WRAs is effective for improving strength properties of the autoclaved SBR-modified mortars.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.156-159
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• 2003

Large amount of binders and high-range AE water-reducing (HRWR) agent are required for self-consolidating concrete in order to achieve flowability and segregation resistance. In this study, the initial permeability of SSC(self-consolidating concrete) until the age of 28 days is measured and compared with those of other SSCs, in which some parts of cement are substituted with fly ash or blast furnace slag. The strengths of SSC samples are also examined along with the permeability change.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.521-526
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• 1997

The Spin Tester(High Speed Balancing and Overspeed Test Facility), which is designed for the quality control of turbine, generator, and rotors was supposed to be constructed with the use of Steel Fiber Reinforced Concrete(SERC) for reducing the risk of accident while operation. However, it was very existence of fiber concrete due to there are two major concern in the SFRC work: one is existence of fiber ball due to inhomogeneous mixing, the other is the segregation of the concrete materials. To avoid these possible problems, the S/a was controlled about 55% to reduce the segregation and the high range AE water reducing agent was used to maintain the slump over the value of 18cm. With these careful consideratons, the SFRC work was done successfully by only using regular equipments like pump car and vibrator.

• Nuclear Engineering and Technology
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• 제31권6호
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• pp.541-547
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• 1999

Corrosion control, in the end-shield cooling system of Wolsung Nuclear Power Plant, is directly related to the control of dissolved oxygen (DO). The current method, being used to deoxygenate the end-shield cooling water, is a chemical treatment by addition of reducing agent, hydrazine, to react with DO. This method has several limitations including high reaction temperature of hydrazine , unwanted explosive hydrogen gas production, and its intrinsic harmful property. A new approach to remove DO using a membrane-based oxygen removal system (MORS) was tried to overcome limitations of the hydrazine treatment. The DO removal efficiency of the MORS was found to be in the range 87% to 98%: The higher vacuum, the lower water flow rate and the higher water temperature tend to increase the DO removal efficiency.

• 한국건축시공학회지
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• 제9권2호
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• pp.85-91
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• 2009

W/C and unit volume, which significantly affect quality of concrete related to strength and durability, are regulated at below $185kg/m^3$ for regular concrete generally used in standard specification for constructions. The aim of this research is to develop chemical admixture and find out its potential use by identifying characteristics of admixtures added to soft concrete and hardening concrete, of which content ratio of component for each type of admixtures is subject to change in accordance with unit volume within KS' allowable range. Sodium gluconate, polyoxyethylene nonylphenyl ether, poly carboxylic copolymer in slump, which is characteristic of soft concrete, are deemed highly sensitive while there is no air entrainment except for $10\sim70%$ in WE, WR component content ratio and NP. In hardening concrete, strength in general showed higher action in compressive strength and tensile strength than in plain strength. Use of proper AE agent and AE water reducing agent at the same time is deemed to be used as chemical admixtures capable of manufacturing high-quality, high-quantity concrete.

• 콘크리트학회논문집
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• 제12권5호
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• pp.111-120
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• 2000

In case of constructing concrete structure under water, generally concrete mixed with antiwashout admixture, high range water reducer, or AE-water reducing agent etc has been manufactured to ensure the quality of antiwashout underwater concrete because of being difficulty in ascertaining construction situation by the naked eye. The properties of high quality antiwashout underwater concrete that were aimed at affluent fluidity, workability and the compressive strength of 450 kgf/$\textrm{cm}^2$ at 28 ages using two types of blended cements are following as;(1) Setting time of antiwashout underwater concretes using blended cements was more greatly delayed than that of control concrete, however, was satisfied with criteria value of "Quality standard specification of antiwashout admixture for concrete".(2) As a test results of slump flow, efflux time and box elevation of head, it was found that workability of high quality antiwashout underwater concrete was improved. (3) Heat evolution amount of OPC was 1.5 times as high as that of two types of bended cements in 72 hours. (4) Suspended solids of antiwashout underwater concrete using blended cements was more than that of control concrete, also compressive strength of high quality antiwashout underwater concrete was very low in early age, but was better than that of control concrete as to increasing ages.

• 한국산학기술학회논문지
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• 제18권2호
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• pp.689-696
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• 2017

기존의 고유동 콘크리트는 높은 분체계로 인해 수화열과 수축의 증대, 비경제적인 강도발현 등의 문제점이 발생하여 일반강도 범위의 콘크리트에는 사용범위가 제한하고 있다. 그러나 공사품질의 향상과 더불어 공사비 절감, 공기단축 등의 이점으로 일반강도 수준의 고유동 콘크리트의 필요성이 대두되고 있다. 이를 위해 본 연구에서는 점성을 최소화하고 재료분리 저항성은 극대화 된 저분체 고유동 콘크리트를 제조하기 위하여 적절한 증점제의 사용방법과 최적 배합을 검토하고 제조 된 콘크리트의 특성을 검토하였다. 다양한 증점제를 대상으로 역학적 특성 평가를 통해 저분체 고유동 콘크리트 제조에 적합한 증점제를 선정하였으며, 그 결과 아크릴계(Acrylic. 이하 AC) 및 우레탄계(Urethane, 이하 UT) 증점제가 재료분리가 발생 하지 않는 범위에서 가장 우수한 성능을 나타내어 가장 적합한 것으로 나타났다. 선정된 AC 및 UT 증점제의 최적 혼입량을 검토하기 위하여 두 물질의 혼합사용 및 고성능 감수제와 일액화를 통한 배합실험을 하였으며, 그 결과 AC 및 UT 증점제의 비율이 5:5인 경우 유동성 증대 및 점성 저감 효과가 증가함에 따라 저분체 고유동 콘크리트에 가장 적합한 것으로 나타났다.