• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.707-714
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• 2001

This paper presents the fundamental study on rational manu(acture of Very High Strength(VHS) concrete using industrial by-products as like silica fume, slag and fly ash. In this study, we had tested various mixing cases to manufacture the VHS concrete(target compressive strength : over 1,000 kgf/$cm^{2}$) which is easily workable (target slump flow : 60$\pm$l0cm), The main variables studied are; 1) test variables to find the optimum replacement ratio of mineral admixture, 2) test variables to find a rational water-binder ratio, a proper binder content, 3) test variables to find the method for reduction of slump loss, 4) test variables to know the influence of air entrainment on frost resistance. From the test results, it is concluded that the rational mix design can be made by using 40% slag, 10% silica fume, and water reducing agent(slump loss reduction type). We found that it is unnecessary to entrain air for freeze-thawing resistance.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2022년도 제66차 하계학술대회논문집 30권2호
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• pp.107-109
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• 2022

본 논문은 건설구조물 안전의 가장 중요한 요소 중 하나인 콘크리트 압축강도 안정성을 확보하기 위한 시스템으로, 콘크리트 구조물을 만들 재료인 레미콘의 수분 감소율에 따른 압축강도 감소 리스크를 관리할 수 있는 모델을 제시하였다. 동일한 물,시멘트비(W/C)로 생산된 레미콘은 현장타설시까지 교통환경으로 인한 도착시간 지연 및 강우, 강설 등 외부적인 요건으로 감수율이 발생하는 리스크가 발생한다. 이로 인해 콘크리트의 압축강도가 저감하는 중대한 문제가 발생한다. 본 연구에서 제시한 알고리즘을 이용하여 현장 타설전 콘크리트 시료의 함수율을 측정하여 감수율이 발생한 제품 발견시, 실시간으로 Operator로 GCM 기반의 Push Alarm을 전송하여 감수율이 반영된 제품을 제공함으로써 구조물의 안전성을 확보할 수 있는 시스템을 모델링하였다. 본 연구는 기존시스템의 문제점을 실시간으로 개선할 수 있는 것으로 건설현장의 구조물 안정성 확보에 효과가 클 것으로 기대된다.

• 한국해안해양공학회지
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• 제15권2호
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• pp.71-79
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• 2003

본 논문에서는 염소이온 침투해석에 사용되는 염소이온 확산계수. 염소이온 고정화 관계식, 증발가능 수량에 대한 일반 예측식들을 제시하였다. 이러한 식들을 염소이온 확산 모델링에 대입하여 그 식들의 유효성을 검토하였다. 상대습도와 양생온도의 염소이온 확산에 대한 영향은 주로 확산계수를 변화시켜 고려한다. 상대습도가 증가하면 염소이온 확산깊이는 증가하고 재령이 경과할수록 상대습도가 확산깊이에 미치는 영향은 커진다. 반면에, 양생온도가 증가하면 확산깊이가 조금 증가하지만 재령이 경과할수록 양생온도가 확산깊이에 미치는 영향은 감소한다. 한편, 염소이온의 고정화에 영향을 미치는 시멘트의 $C_3$A양이 증가하면 표면에서는 고정염소이온의 증가로 인해 전체 염소이온량이 증가하지만 깊이가 깊어질수록 확산되는 자유염소이온의 감소로 인해 전체 염소이온량이 감소한다. 물-시멘트비가 감소하면 염소이온의 확산깊이는 급격히 감소하고 염소이온의 확산을 막는 가장 효과적인 방법은 물-시멘트비를 감소시키는 것임을 알 수 있다

• International Journal of Concrete Structures and Materials
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• 제11권2호
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• pp.301-313
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• 2017

This paper presents the fibre-matrix interfacial properties of hooked end steel fibres embedded in ultra-high performance mortars with various water/binder (W/B) ratios. The principle objective was to improve bond behaviour in terms of bond strength by reducing the (W/B) ratio to a minimum. Results show that a decrease in W/B ratio has a significant effect on the bond-slip behaviour of both types of 3D fibres, especially when the W/B ratio was reduced from 0.25 to 0.15. Furthermore, the optimization in maximizing pullout load and total pullout work is found to be more prominent for the 3D fibres with a larger diameter than for fibres with a smaller diameter. On the contrary, increasing the embedded length of the 3D fibres did not result in an improvement on the maximum pullout load, but increase in the total pullout work.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.585-588
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• 2006

The environment-friendly building material, photocatalyst/scoria/loess concrete, was prepared using scoria and loess (which have merits as building materials) and photocatalyst (which has the functions to compose the environmental contaminants and of self cleaning). In order to apply this material as a building material, the compressive and flexible strengths, and water absorptivity (which have been set by Korea Industrial Standard) were measured. The optimum mixing ratio of photocatalyst/scoria/loess concrete was obtained at the condition of $393kg/m^3$ of coarse aggregate, $802kg/m^3$ of fine aggregate in case of scoria, $80kg/m^3$ of loess, $12kg/m^3$ of photocatalyst, $400kg/m^3$ of cement, and $2kg/m^3$ of AE water reducing agent. The photocatalyst/scoria/loess concrete prepared by above mixing ratio of raw materials showed 25 MPa of compressive strength, $3.8{\sim}4.6$ MPa of flexible strength and $11.4{\sim}12.0%$ of water absorptivity, indicating that the quality of this material was suitable for Korea Industrial Standard (more than 21 MPa for compressive strength, more than 2.0 MPa for flexible strength in case of lightweight aggregate, and less than 15 % for water absorptivity in case of clay brick) for using as a building material.

• 상하수도학회지
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• 제27권2호
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• pp.241-249
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• 2013

Ethanolamine (ETA) is widely used for alkalinization of water in steam cycles of nuclear power plants with pressurized water reactor. When ETA contained wastewater was released, it could increase COD and T-N. The treatment of the COD and T-N from ETA wastewater was investigated using the GAC as particle electrodes in three-dimensional electrode reactor (TDE). This study evaluated the effectiveness of GAC as particle electrode using different packing ratio at 300 V. The results showed that GAC-TDE could reduce ETA much more efficiently than ZVI-TDE at the mass ratio of GAC to insulator, 1:2. Additionally, The effect of applied electric potential to COD and T-N reduction was investigated. The results showed the high COD, T-N reduction and current efficiency at the low electric potential. Using the GAC-TDE will provide a better ETA reduction with reducing electrical potential dissipation.

• 한국지역사회생활과학회지
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• 제16권1호
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• pp.59-64
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• 2005

This study is to find out effects of hot water soluble extract from green tea, one of the Korean favorites, on the calcium metabolism and bone strength in body. To do so, calcium, phosphate, creatinine concentration and ALP activity in blood and the content of calcium and ash in the organ, the length, weight, strength in bone were measured. In addition, to find the calcium metabolism, the level of calcium intake, excretion, retention were measured. Twenty male Sprague-Dawley rats were divided into two groups and isoloated soy protein was provided as the source of protein and CaCO₃ was provided as the source of calcium. 0.5% hot water soluble extract from green tea was provided to the green tea groups and for the control group deionized water was provided. The results are as follows ; 1. There is no difference between the experimental groups in diet intake, weight gain, and the feed intake. 2. Feed efficiency ratio was low in the group which hot water soluble extract from green tea was provided. 3. There is no difference between groups the level of calcium, phosphorus, creatinine and ALP activity in serum. 4. There is no difference between groups weight, contents of ash and calcium in kidney and liver. 5. There is no difference between groups in calcium intake, absorption, excretion, and retention. 6. There is no difference between groups weight, length and strength in bone. In summary, when hot water soluble extract from green tea was provided with the amount of 150-200mg, which is taken when people generally drink as favorite tea, weight gain was reduced due to the decrease of feed efficiency ratio. However, it did not affect the availability of calcium in body at all. Thus, even if a big quantity of green tea powder or solid of hot green tea extract is not provided, the quantity obtained when people drink green tea lowers the feed efficiency ratio without reducing availability of calcium in body.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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• pp.179-184
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• 2011

The development of new energy has attracted consideration attention due to the high oil price and environmental problems. In advanced country, they have tried to carry out a long range plan for energy. We need to develop new energy for Low Carbon Green Growth in Korea. The building is 30% among ratio of energy consumption in Korea. And in the past, heating energy was high ratio for energy using at home. But recently, the demand for cooling energy keeps growing due to rising average temperature on the earth and improvement of life quality. In this situation, the energy of lake water and ocean water has studied to utilize in advanced country because of low temperature at underwater. But the study for deep water is still a lot left to do. In this study, we analyzed district cooling system and the present condition. Analyzing the deep lake water cooling system in Toronto, we found an application of district cooling system using deep ocean water. Deep lake water uses heat source for district cooling and water source for city in Toronto. So reducing the initial cost, this city had economic effect. When DLWC was applied at existing building, the heat exchanger was installed instead of cooling tower and refrigerator. And the heat exchanger used to connect main pipe with cool water on city. System using deep ocean water can be applied as a similar way to supply cool water from lake to building.

• 한국재난정보학회 논문집
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• 제20권1호
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• pp.20-31
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• 2024

연구목적: 고강도 콘크리트 연구개발은 건축물의 고층화를 가능케 하고, 단면 축소로 구조물 자중이 경감되어 보와 슬래브 두께를 얇게 함으로 보다 많은 층수를 축조할 수 있었으며, 넓은 유효공간이 확보되고, 기초 저면 지정에 사용된 자재 및 철근과 콘크리트 양을 절감하는 효과를 가져올 수 있다. 연구방법: 현장시공 및 품질측면에서는 낮은 물결합재비 배합를 연구하므로 건조수축 발생 저감 효과를 확인할 수 있고, 콘크리트 표면의 블리딩 최소화 연구를 통하여 그 효과를 검증할 수 있다. 연구결과:고성능감수제 사용에 의한 유동성 증진으로 자체 충전성이 높아 현장 시공 용이성을 확인하고, 콘크리트의 조기 강도 발현으로 거푸집 탈형 시간을 단축시킬 수 있는 장점을 확인하였다. 이러한 실험결과 자료는 초고층 건축물에서는 설계기준강도 100MPa급 이상의 초고강도콘크리트의 현장 적용이 확대될 수 있다. 본 연구를 통하여 국내에서도 120층 이상의 초고층 건축물 현장 적용성이 고려된 130MPa급 이상의 초고강도 콘크리트를 현장에서 실제 적용 가능성 여부를 실험, 평가하였다. 결론:본 연구에서는 초고강도의 현장적용 가능성을 확인하기 위하여 여러 가지 방법의 실내기초 실험으로 연구되어진 최적의 배합비를 찾아서 모의부재 예비 실험 후 실물크기와 유사한 모의부재에 130MPa 초고강도콘크리트를 레미콘 공장에서 생산하여 현장 펌프 압송 타설하고, 콘크리트의 유동성 및 강도 발현과 수화열에 관하여 현장 적용성을 실험한 연구다.

• 콘크리트학회논문집
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• 제11권4호
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• pp.95-105
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• 1999

When superplasticizer is added to manufacture flowing concrete, the base concrete usually needs the adjustment to assure the sufficient fines contained to obtain flowable consistency without excessive bleeding or segregation. However, this may not only increase the cost, but also cause inconvenience in producing the base concrete. In this paper, the experiments are performed on normal base concrete to achieve a segregation-reducing flowing concrete by adding superplasticizer mixed with viscosity agents and AE admixtures. Three kinds of superplasticizer and two kinds of viscosity agent are selected. According to the results, with regard to the performance and cost of the admixtures, melamine type superplasticizer combined with the PEO viscosity agent and AE admixtures at the ratio 1:0.28:0.001 can acquire good quality and reduce the cost in producing the flowing concrete. With proper addition of combined superplasticizer, even though water to cement ratios of the base concrete are different, the segregation-reducing flowing concrete could be also achieved without reproportioning of the base concrete. However, it would be more desirable if the superplasticizer could be adjusted, before it is put into the practical use in order not to cause some other problems, such as rapid rate of slump loss and retarding of setting time.