• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.76-82
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• 1997

Recently as the development of a large-scale ocean structure or ocean is in progress, the importance of underwater concrete construction came to the fore. However, a problem with this underwater concrete construction is the segregation of cement and aggregate occurs when concrete is poured into the underwater. However, recently as an adhesiveness of the constituents of fresh concrete is increased even in our country, antiwashout concrete admixture were developed. The antiwashout concrete admixture can reduce the segregation significantly. Although this antiwashout underwater concrete is superior to the traditional underwater concrete in terms of durability, watertightness, stability, etc. But it is still unsatisfied due to the lack of criterion or construction experiences. Furthermore, because of an insufficiency of natural aggregate, the development of replacing aggregate came to be necessary. Accordingly, the purpose of this study is to investigate the feasibility of sea sand as a replacing aggregate and the characteristic change of antiwashout underwater concrete using river sand, sea sand, and blended sand (river sand:sea sand=3:7) through experimental researches.

• 콘크리트학회지
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• 제7권6호
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• pp.224-232
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• 1995

최근 일부 외국에서는 종래의 수중 콘크리트와 다른 관점으로부터 수중에서 쉽게 분리되지 않고 타설방법도 용이한 특수 혼화제가 개발되어 실험과 시공에서 성공하였고, 이런 특수 콘크리트(수중 비분리 콘크리트)는 점차 사용 규모와 시공 방법이 확대되고 있는 추세이다. 본 논문에서는 수중 비분리 콘크리트에 대한 성공적인 실험, 시공사례를 참고하여 수중 비분리성 혼화제 및 다른 혼화제의 첨가 방법을 달리하였을 경우, 수중 비분리 콘크리트의 물성변화를 검토하였고, 비교적 정온 상태의 해상 환경에 적용할 수 있는 수중 비분리 콘크리트의 최적 배합을 결정하였다.

• 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.

• 콘크리트학회논문집
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• 제12권5호
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• pp.25-34
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• 2000

When concrete is placed underwater, it is diluted with separating cementitious material and as a result the quality of concrete becomes poor. To solve this problem, antiwashout underwater concrete is increasingly used for the construction and repair of the concrete structure underwater. The objective of this study is to investigate the characteristics of antiwashout underwater concrete as to the mix proportion, casting and curing water through experimental researches. The unit weight of water and cement, water-cement ratio, fine aggregate ratio, unit weight of antiwashout underwater agent and superplasticizer, and casting and curing water were chosen to measure the suspended solids, pH, air contents, slump flow, unit weight of hardened concrete, and compressive strength. From this study, the incremental modulus at mix proportion design and unit weight of antiwashout underwater agent were increased more than fresh water, and it is a optimum mix proportion that the unit weight of water(and cement) is 230kg/$\textrm{m}^3$(460kg/$\textrm{m}^3$), waterOcement ratio is 50%, fine aggregate ratio is 40%, unit weight of antiwashout underwater agent is 1.2% of water contents per unit weight of concrete, and unit weight of supeplasticizer is 2.5% of cement contents per unit weight of concrete when the antiwashout underwater concrete is used for the underwater work of ocean.

• 산업경영시스템학회지
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• 제44권3호
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• pp.10-21
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• 2021

Recently, the demand for atypical structures with functions and sculptural beauty is increasing in the construction industry. Existing mold-based structure production methods have many advantages, but building complex atypical structures represents limitations due to the cost and technical characteristics. Production methods using molding are suitable for mass production systems, but production cost, construction period, construction cost, and environmental pollution can occur in small quantity batch production. The recent trend in the construction industry calls for new construction methods of customized small quantity batch production methods that can produce various types of sophisticated structures. In addition to the economic effects of developing related technologies of 3D Concrete Printers (3DCP), it can enhance national image through the image of future technology, the international status of the construction civil engineering industry, self-reliance, and technology export. Until now, 3DCP technology has been carried out in producing and utilizing residential houses, structures, etc., on land or manufacturing on land and installing them underwater. The final purpose of this research project is to produce marine structures by directly printing various marine structures underwater with 3DCP equipment. Compared to current underwater structure construction techniques, constructing structures directly underwater using 3DCP equipment has the following advantages: 1) cost reduction effects: 2) reduction of construct time, 3) ease of manufacturing amorphous underwater structures, 4) disaster prevention effects. The core element technology of the 3DCP equipment is to extrude the transferred composite materials at a constant quantitative speed and control the printing flow of the materials smoothly while printing the output. In this study, the extruding module of the 3DCP equipment operates underwater while developing an extruding module that can control the printing flow of the material while extruding it at a constant quantitative speed and minimizing the external force that can occur during underwater printing. The research on the development of 3DCP equipment for printing concrete structures underwater and the preliminary experiment of printing concrete structures using high viscosity low-flow concrete composite materials is explained.

• 콘크리트학회지
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• 제8권5호
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• pp.179-187
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• 1996

최근 해양 개발의 추세에 따라 많은 수중콘크리트 구조물이 건설되고 있다. 이에 따라 일부 외국에서는 종래의 치기방법 개선 위주의 연구에서 벗어나 수중에서 쉽게 분리되지 않는 특수 혼화제의 개발에 성공함으로써 공기중에서 치는 콘크리트와 대등한 품질을 갖는 수중콘크리트의 실험과 시공에 성공하였지만 아직 국내에서는 연구실적이나 시공사례가 없다. 본 논문에서는 수중불분리 콘크리트에 대한 성공적인 실험, 시공사례를 참고로 실내 실험을 실시하여 수중불분리성 혼화제 및 다른 혼화제와의 상호작용으로 인한 수중불분리 콘크리트의 물성변화를 정량적으로 평가하였고, 정온 상태의 해상 환경에 적용할 수 있는 최적의 배합을 결정하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 기초기술학술발표회
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• pp.103-117
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• 2002

During the installation of drilled shafts in very soft ground, to keep the pile shape and to central concrete quality, casing method (wrinkled pipe and embedded steel pipe) and non-casing method have been used. In the construction cost, non-casing method was the most economical. When the wrinkled pipe and the embedded steel pipe casing method are used, an increase of 133% and 123% in the construction cost could be seen. When concrete for drilled shaft was placed under groundwater, underwater unseparation concrete would be used to restrain the concretes's material separation and to control the concrete quality. On the condition of required unseparable and (lowing property was assured, use of less amount of mixed material and flowing material must be recommended.

• 한국건축시공학회지
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• 제3권3호
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• pp.91-97
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• 2003

At present, the antiwashout underwater concretes are used as popular construction materials in European countries, the United States and Japan. The water-soluble polymers in the antiwashout underwater concretes provide excellent segregation or washout resistance, self-compaction and self-leveling property to the concretes. The purpose of this study is to recommend to optimum mix proportions of antiwashout underwater concretes according to compressive strength of 300kgf/$\textrm{cm}^2$ to 500kgf/$\textrm{cm}^2$. The antiwashout underwater concretes are prepared with various unit cement content, unit water content, sand-aggregate ratio, unit antiwashout agent and superplasticizer content. And they are tested for flowability, and compressive strength. From the test results, it is possible to recommend the optimum mix proportions of antiwashout underwater concretes according to compressive strengths within the range of 300kgf/$\textrm{cm}^2$ to 500kgf/$\textrm{cm}^2$.

• 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.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.41-46
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• 2000

In recently, though the development of antiwashout admixture, if's possible to construct in underwater with the concrete which is improved segregation resistance of material, filling and self-leveling. It is generally to use this method with Europe and Japan as the central figure, and also the construction case is reported in korea. There's some advantages to add the fly ash in plain concrete. The objective of this study is to find the characteristics of fresh underwater antiwashout concrete which is followed by the blend rate of fly ash.