• 한국해양공학회지
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• 제15권4호
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• pp.120-125
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• 2001

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$^{\circ}C$ 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 underseawater concrete could be prolonged.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.153-159
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• 1999

The objective of this study was to investigate the bond strength properties of antiwashout underwater concrete. The fine aggregate(river sand, blended sand (river sand : sea sand = 1 : 1), condition of cast and cure(sea water, fresh water), and compressive strength of proportion(210kgf/$\textrm{cm}^2$ ~ 330kgf/$\textrm{cm}^2$) were chosen as the experimental parameters. The experimental results show that the underwater segregation resistance was increased, but flowability (slump flow) and air contents were decreased as the compressive strength of proportion increased. Bond strength of antiwashout underwater concrete was similar to plain concrete. From this study, rational analytic formula for the modulus of rupture and bond stress are to be from compressive strength of concrete.

• 콘크리트학회논문집
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• 제16권2호
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• pp.283-291
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• 2004

Recently, the construction of underwater structures has been gradually increased, but underwater concrete got some problems of quality deterioration and water contamination around cast-in-situ of construction. In addition, massive underwater structures such as LNG tank, underwater concrete structures of large and continuous high- strength subterranean wall under water are being demanded lower heat of hydration. In this paper, the mechanical properties of high-strength antiwashout underwater concrete (HAWC) containing with two kinds of mineral admixtures respectively were investigated. On the basis of these results, the pH value and suspended solids of HAWC manufactured in the mock-up test were 10.0$\Box$11.0 and 51 mg/${\iota}$ at 30 minutes later, respectively, initial and final setting time were about 30,37 hours, and the slump flow was 530$\pm$20Tm. In the placement at a speed of $27 m^3/hr$, there was no large difference in flowing velocity with or without reinforcing bar, and flowing slope was maintained at horizontal level. Compressive strength and elastic modulus of the cored specimen somewhat decreased as flowing distance was far; however, those of central area showed the highest value.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.683-688
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• 2001

In case of constructing the concrete structures under seawater environment, the concrete suffers from deterioration due to penetration of various ions such as chloride, sulfate and magnesium in seawater. Tn the present study, Immersion tests with artificial seawater were carried out to investigate the resistance to seawater attack of antiwashout underwater concrete. From the results of compressive strength, it was found that blended cement concrete due to mineral admixtures such as fly ash(FA) and ground granulated blast-furnace slag(SGC), were superior to ordinary portland cement concrete with respect to the resistance to seawater attack. Moreover, XRD analysis indicated that the formed reactants of ordinary portland cement paste by sulfate and magnesium ions led to the deterioration of concrete. As expected, however, the blended cements with FA or SGC have a good resistance to seawater attack. This paper would discuss the mechanism of seawater deterioration and benefical effects of antiwashout underwater concretes with mineral admixtures.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.345-346
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• 2010

수중불분리 콘크리트의 품질은 혼화제의 성능 및 배합비와 같은 변수들에 영향을 받으며, 이들 중 혼화제의 성능은 수중불분리 콘크리트의 품질에 많은 영향을 주고 있다. 따라서, 본 연구에서는 수중불분리성 혼화제를 사용한 콘크리트의 슬럼프 플로우, 응결시간, 압축강도 및 수중분리도를 측정하여 수중불분리성 혼화제의 성능을 평가하였다. 그 결과, 수중불분리성 혼화제를 사용한 콘크리트는 플레인 콘크리트보다 유동성, 압축강도 및 수중불분리도와 같은 콘크리트의 품질이 개선되는 것으로 나타났다.

• 콘크리트학회논문집
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• 제17권3호
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• pp.455-464
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• 2005

수중불분리성 콘크리트의 적용 사례가 점차 증대되고 있는 추세임에도 불구하고 역사가 짧은 탓으로 신뢰성 등에 대한 문제점을 지적하고 있다 특히 수중불분리성 콘크리트는 동결응해에 대한 저항성이 매우 취약한 것으로 알려져 있어 일본토목학회에서는 동결융해작용을 받는 지역에서는 사용해서는 않된다고 규정하고 있다. 본 연구에서는 수중불분리성 콘크리트의 내구성을 향상시키기 위한 목적으로 광물질혼화재 3종류로 제조한 수중불분리성 콘크리트의 기초물성과 동결응해 저항성에 대한 실험을 실시하였다. 본 연구실험결과 FA20 및 SG50의 유동성 및 장기강도는 기준콘크리트 보다 양호한 경향을 보인 반면 현탁물질량은 약간 큰 값을 나타내었다. 한편 MK10의 경우, 빠른 수화반응으로 현탁물질량과 압축강도는 양호한 결과를 나타내었으나 유동성은 다소 떨어지는 문제점이 있었다. 한편, 수중불분리성 콘크리트의 동결응해 저항성은 셀룰로오스계 수중불분리성 혼화제에 의한 크고 불규칙한 갇힌공기 때문에 광물질혼화재를 혼합한 경우에도 효과가 적었으나 SG50과 MK10의 공기량 $6{\pm}0.5\%$의 경우, 동결응해 저항성이 약간 향상되는 결과를 얻었다. 그러나 고로슬래그 미분말의 분말도를 달리한 경우 분말도가 증가할수록 활성도가 높아져 동결응해 저항성이 향상되는 경향을 나타내었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.324-329
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• 1998

Recently the use of the underwater concrete with the antiwashout admixture is increased considerably. When we intend to apply it to the field, we must consider the water temperature effect. In this study, we investigate the properties of setting time, early strength, hydration temperature history and core strength with the antiwashout underwater concrete in the water temperature 8$^{\circ}C$, 14$^{\circ}C$ and 22$^{\circ}C$ respectively. As a result of experiment, as the water temperature is decreasing, setting time is delayed twice of three times and early strength is lower from 10% to 50%. Therefore to compensate the decrease of the early strength, we used the accelerator and investigated the concrete properties.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회 논문집(I)
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• pp.277-283
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• 1998

In this study we changed W/C into 45, 50, 55, 60%, mixed sea sand which is often used as a replacing aggregate according to the lack of recourse with river sand in the ratio of 5:5 and producted antiwashout underwater concrete. We measured slump flow, air value, pH and suspension in the fresh concrete. After testing each W/C through unit weight and compressive strength of specimen which is produced and cured in the air and salt water it was founded that if sea sand was properly used after salt manufacturing, there will be no bad influence to antiwashout underwater concrete. The characteristic of them showed excellent, when W/C was 50%.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.941-946
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• 2001

In this study, three kinds of fine aggregate (river sand, sea sand, crushed sand) were used and four different s/a (38%, 40%, 42%, 45%) were applied separately to this experimental for get the conclusion written below. Regardless of kinds of fine aggregate and casting-curing condition, maximum unit weight is seen at 40% of s/a and also to be seen in case of crushed sand. It's for that specific gravity of crushed sand is bigger comparatively than river sand and sea snad's one. Compressive strength is measured river sand, crushed sand, sea sand by order of size ; Regardless of variation of s/3, casting-curing condition and age. Compressive strength recorded maximum when s/a is 42% whatever sort of fine aggregate are. As the result, according to references, the optimum s/a of underwater antiwashout concrete is 40% but in this study, from compressive strength of view, the optimum s/a of underwater antiwashout concrete is 42%.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.533-536
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• 2003

The objective of in this study makes investigation into the characteristics of antiwashout underwater concrete as to mix proportion, casting and curing water through experimental researches. in this study, sea sand is blended with river sand, crushed sand is blended with river sand and sea sand as to investigate the quality change and characteristics of antiwashout underwater concrete with variation of blend ratio of sea sand and crushed sand(0, 20, 40, 60, 80, 100%). Higher compressive strength is measured following the order of river sand, sea sand, crushed sand regardless of age and casting condition. Except for case of using river sand, blended ratio of 40% is appeared on most compressive strength.