• Journal of the Korea Institute of Building Construction
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• v.15 no.4
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• pp.375-381
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• 2015

In this study, high performance concrete of C60 and C80 were applied to a super tall building and those had satisfactory properties of fresh and hardened concrete to the requirements even changes according to time. Especially the evaluation and analysis of the relation of the rheological properties and puMPability of high performance concrete, C60-14 which was applied to the height of from 500m to 575m in the building, was carried out bymeasuring pumping pressure and pumping speed, testing concrete properties at before and after pumping. As results, themax. pumping pressure showed increase of 5% at every 25m higher pumping and the average pumping speed showed the above $25m^3$ per hour whichmeans proper productivity. Additionally it was verified that the loss of slump flow after pumping was increased according to plastic viscosity values and the increment of temperature through concrete pumping.

• Journal of the Korea Institute of Building Construction
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• v.15 no.3
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• pp.291-297
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• 2015

In this study, the evaluation and the analysis of the correlation between rheological properties and pumpability of high performance concrete, C80A which was applied to the height of from 200 m to 350 m in a super tall building, was carried out by measuring pumping pressure and flow rate, testing concrete properties at before and after pumping. As the results, C80A had satisfactory properties of fresh and hardened concrete to the requirements even after pumping and the maximum pumping pressure showed increase of 10~15% at every 50m higher pumping and the average flow rate showed the above $25m^3$ per hour which means proper productivity. Additionally it was verified that pumping pressure and friction factor in pipeline are inversely proportional to slump flow and showed a tendency to increase according to the higher T-500 value.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.547-548
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• 2009

Fiber reinforcement has been being widely used in concrete to enhance the mechanical properties and to reduce the micro-cracking caused by plastic and drying shrinkage. While researches has been focused on the benefits of fiber reinforcement, the properties of fiber reinforced concrete are strongly dependent on the type, shape and the amount of fibers in concrete.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.509-516
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• 2012

The aims of this research is to develop a fire resistant admixture to enhance high-pressured pumping of high-strength concrete (HSC) with a compressive strength of 60~80 MPa. Generally, the efficiency of HSC high-pressured pumping is dramatically reduced due to entanglement of short fibers added to prevent fire spalling. Therefore, the fire resistant admixture that can facilitate pumping of fire resistant HSC is urgently needed presently. The fire resistant HSC mix is comprised of Polypropylene fiber, Nylon fiber and Polymer powder. The test results showed that the slump-flow was improved by approximately 70% of the HSC without fire resistant admixture. However, the air void content was increased slightly due to the addition. The standard design compressive strength at 28-days was satisfied, while its flexural strength was similar to the concrete without the admixture. Since the flexural strength was 12~15% of its compressive strength, the general trend of flexural to compressive strength ratio in normal concrete was maintained. Even though its elastic modulus was decreased by adding the admixture, the study results showed that the concrete can be used for construction since all of the test results exceeded the code requirements.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.442-449
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• 2017

In this study, a method to inject small amount of activation agent from the outside of the pipeline to the inside wall of the pipe was newly proposed to enhance pumping efficiency of cementitious materials. The activation agent is injected into the slip-layer, which is generally formed in the vicinity of the inside wall of the pipe during pumping cementitous materials. Through the injections, it is expected to decrease viscosity of slip-layer, namely, the friction between the mateirals and the pipe. The proposed method was verified by lab-scale pumping tests with mortars having water to cement ratio of 47%. The tests were performed with two different type of activation agents(superplasticizer and anionic surfactant) and three different amount of the agents(0.14, 0.28, 0.42% of the mortar volume). The compressive strength were measured with and without injecting the activation agent, and the internal pressures of pipeline were measured. When the anionic surfactant was used, there was no change in the compressive strength. As the amount of anionic surfactant increased, the pumping pressure decreased up to 71.4% at the maximum.

• Journal of the Korea Institute of Building Construction
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• v.10 no.5
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• pp.113-119
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• 2010

Fire resistance and field tests for high-strength concrete(HSC) of 80MPa were carried out to evaluate whether or not it shows the same material properties even in the field condition of being mass-produced and supplied. As a result, it was found that fire resistant HSCs containing composite fiber(NY, PP) of 0.075% have great resistance to fire and spalling. In the field test, before the pumping air contents, slump flow, U-box, L-flow, compressive strength, gap of hydration temperature of interior and exterior of specimen and placing ratio per hour satisfied the required properties of HSC. However, after the pumping of HSC, as slump flow and L-flow were slightly less than required criterion, they need to be improved. In terms of hydration temperature of HSC, it was found to satisfy the related criterion. Packing ability as well as placing ratio per hour of HSC, which was about $44m^3$, show outstanding results. If slump flow of developed ternary HSC is improved after the pumping it can be useful for the construction of high-rise buildings.

• The magazine of the Korean Society for Advanced Composite Structures
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• v.5 no.3
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• pp.38-52
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• 2014

도시주민생활에 없어서는 안 될 주요한 사회간접자본시설인 하수도, 하수도처리시설 등의 콘크리트 구조물에 대한 부식열화는 현재 세계 각국에서 급속히 진행되고 있다. 콘크리트 구조물은 반영구적인 것으로 인식하고 있다. 그러나 각종 열화 인자에 의해 구조물의 사용수명은 급속히 단축된다. 하수시설 내에서는 황산이외에도 다양한 염류에 의하여 콘크리트구조물이 부식될 가능성이 있지만 황산에 의한 부식이 가장 대상범위가 넓고 부식속도가 빠르기 때문에 부식현상이 발견되면 급속하고 적절한 대응조치가 필요하다. 열화예측결과 및 구조물의 공용연수를 감안한 신뢰성이 높은 공법의 도입이 필요하며 이러한 조건에 적합한 유기재료와 무기재료의 복합 특성을 발휘하는 갱생공법에 사용되는 주요 소재의 실험적 특성에 관하여 고찰하였다. 그 결과 경질염화비닐(이하 프로파일)은 내외수압 저항성에서 3분간 $1kgf/cm^2$의 압력에도 누수 및 압력의 이동이 없었으며 약품침지에 따른 중량변화량이 $0.2mg/cm^2$이하로 산에 대한 변화량은 거의 없었다. 주입재인 모르타르의 산성에 대한 저항성은 일반 콘크리트에 비해 우수하였으며 기존 모르타르에 비해 비확선성 또한 우수하였다. 장거리압송시험은 200m까지 안정적인 압송이 가능하여 이 기술에 필요한 요구 성능을 확보한 것으로 나타났다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.23-26
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• 2006

The study about the concrete to use recently a light weight aggregate, processed actively. And concrete pumping with a high pressure pump has been popularized, the mechanical development, such as high pressure pumps or pipes, is progressing rapidly. Concrete placing by pumping has the advantage of the reduction of the construction period with workability, easiness of work and the increase of placing, but the quality variation of concrete is caused by pumping is seldom considered, including the increase of the pipe length by high-rising and large-sizing, there by the loss of the unit quantity of water, with pumpability or workability deteriorated. In this research, we will compare and analyze before pumping and after pumping samples of ready-mixed light weight concrete. The result of study as follow. The case of a light weight concrete which the low slump is more decrement compared with high slump light weight concrete in after pumping samples. After pumping the water by pressure of a pump was absorbed to the aggregate inside, and it showed an increase of compression strength about $5{\sim}20%$.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.395-396
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• 2010

The purpose of this research is that development of fire-high resistance concrete for high-rise buildings is carried out with a test, which is for confirmation of fire-resistance capacity of 80MPa high-strength concrete. In this test, self-developed Polymix to confirm fire-resistance capacity of high-strength concrete in domestic high-rise buildings recently is applied.

• Electrical & Electronic Materials
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• v.5 no.2
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• pp.157-165
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• 1992

전력설비를 비롯하여 모든 생산설비나 공공 기간설비 등의 설계, 운용, 건설은 설비의 목적달성에 충분한 기능을 가지며 가능한 한 저렴하고 효율적으로 이루어져야만 된다. 전력계통 운용상 계획된 송전선은 필요로하는 전력을 발생지점에서부터 소비지점까지 가장 경제적 효율적으로 전송시킬 수 있는 최적설계를 이루어야 한다. 도시미관, 소음 등의 환경과의 조화, 변전소용 부지의 문제, 운전보수나 건설공사비의 저렴화, 안정성, 신뢰성등의 문제를 가스절연기기가 해결할 수 있으므로 최근 가스절연변전소가 급속히 보급되고 있다. 고전압 대전류를 취급하는 초고압송전용 전력기기의 성능향상과 소형경량화, 안전성, 환경조화성 등을 실현시키기 위해서는 양질의 전기절연을 이룩하여야만 한다. 결국 전기절연재료기술이 양질의 전기를 공급할 수 있다고 해도 과언이 아닐 것이다. 즉 초고압전력계통의 구성에 대하여도 절연재료의 성능과 합리적 설계가 기반기술로 대두하게 된다. 따라서 전력계통의 초고압화도 재료기술과 직결되며 현재 우리나라의 실정에서는 특히 취약한 신절연기술에 대하여 보다 심층적인 연구가 수행되어야 될 것이다.