• 한국환경과학회지
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• 제15권2호
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• pp.185-191
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• 2006

In this paper, removal time of side form from concrete using OPC(ordinary Portland cement) and FAC(fly ash cement) are proposed by appling logistic model, which evaluates the strength development of concrete with maturity. W/B, types of cement and curing temperatures are adapted as test parameters. The estimation of strength development by logistic model has a good agreement between calculated values and measured ones. As for the removal times of form works suggested in this paper, as W/8 increases, curing temperature decreases and fly ash is used, removal time of side form is prolonged. Removal time of form from concrete using OPC suggested in this paper is shorter $2.5\~3.5$ days than those of KASS-5 (Korean Architectural Standard Specifications-5) in the range of over $20^{\circ}C$. And in the range of $10\~20^{\circ}C$ removal time of form is shorter than that of KASS-5 by as much as $4\~4.5$ days. The use of FAC results in an increase in removal time of form compared to that of OPC by about 1 day.

• 대한토목학회논문집
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• 제38권1호
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• pp.19-28
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• 2018

거푸집의 탈형 시기는 콘크리트 구조물의 품질과 공사기간, 공사비에 영향을 주는 직접적인 요인으로 콘크리트 구조물의 안전성과 경제성을 확보하는데 중요한 요소이다. 국내 규정에서 거푸집 존치에 대한 규정을 제시하고 있으나 조기에 거푸집을 해체하여 콘크리트의 품질이 저하되고 있다. 이는 양생조건에 대한 이해가 부족하고 공사기간이 단축되길 원하기 때문이다. 따라서 본 연구에서는 콘크리트의 거푸집 탈형시기에 따른 양생조건이 압축강도에 미치는 영향을 시험을 통하여 평가하였다. 연구 결과 거푸집의 12시간 후 조기 탈형은 콘크리트의 28일 압축강도를 최대 약 40% 정도까지 저하시켰으며, 거푸집을 28일 동안 장기간 존치할 경우에는 28일 표준압축강도 대비 약 7%의 강도저하를 가져왔다. 결론으로 본 논문에서는 양생온도를 등가재령으로 고려하여 거푸집 해체 시기에 따른 콘크리트의 압축강도 추정식을 제안하였다. 이 제안식은 현장에서 거푸집 제거 후의 콘크리트 압축강도 평가에 활용될 수 있다.

• 콘크리트학회논문집
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• 제16권3호
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• pp.327-334
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• 2004

본 연구에서는 초기재령에서 고강도콘크리트의 압축강도 발현 특성 검토 및 해석 그리고 콘크리트와 거푸집간의 부착강도 특성을 분석하며, P형 슈미트해머를 이용한 반발도와 압축강도간의 상관관계를 검토하므로서 실무의 고강도콘크리트 측면 거푸집 탈형과 연관한 관련규정의 적합성을 재검토하고, 아울러 거푸집제거와 연관한 효율적인 품질관리 방법에 대하여 제안하고자 한다. 연구결과에 따르면, W/B가 증가할수록 응결시간은 감소하는 것으로 나타났으며, 본 연구의 범위에서 로지스틱 모델에 의한 강도증진 해석 결과 압축강도 8MPa를 발휘하는 시간과 적산온도는 17${\~}$20시간, $21{\~}25^{\circ}D{\cdot}D$ 정도로 나타났다. 거푸집과 콘크리트의 부착강도는 종결시점에서 가장 크게 나타났으며 그 이후에는 감소함을 보였고, 거푸집에 부착되어 박리되는 콘크리트의 양은 응결이전에 크게 나타났으며, 그 이후에는 점차적으로 감소하는 경향을 보였다. P형 슈미트해머에 의한 반발도 실험결과 압축강도 발현시점보다 약 2${\~}$3시간 정도 빠르게 측정할 수 있으며, 반발도가 32 이상이면 측면 거푸집을 탈형 할 수 있는 시기로 품질관리가 가능할 것으로 판단되었다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2003년도 학술.기술논문발표회
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• pp.99-102
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• 2003

This study discusses the determination of removal time of forms with early strength development in high strength concrete. According to the results, as W/B increases by 10％, the setting time is shortened by about 2 hours. The time when compressive strength of 8 MPa is gained is about 20 hours. Bond strength between form and concrete is highest around final setting time, but decreases drastically after that. Amount of concrete sticking on the form is large before setting, but after that, it is little. The rebound value of P type schmidt hammer is measured faster by 2-3 hours than compressive strength. It is also confirmed that the removal of forms is possible when the rebound value of P type schmidt hammer is more than 34

• 한국방재학회 논문집
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• 제6권1호
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• pp.1-7
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• 2006

항만공사에 사용되는 케이슨의 제작은 slip-form을 사용한 연속타설공법을 적용하고 있다. 국내 공사에서는 동절기에도 소요의 압축강도를 발현하기 위해서 양생시간의 조절과 slip-form 자체에 온도조절이 가능한 가열보온기기를 설치하여 시공하고 있다. 외기온에 따른 최적 양생온도 및 탈형시간을 추정하여 다음과 같은 결론을 도출하였다. 양생온도 $30^{\circ}C$에서 6시간의 양생시간을 거쳐 탈형되는 것이 압축강도의 발현이나 탈형의 부착 등의 문제가 없는 것으로 판단된다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 추계 학술논문 발표대회 논문집
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• pp.91-94
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• 2006

The way to shorten a construction period is considered to an very important technology development element as reducing the formwork removal periods with promoting strength revelation own concrete. This study executed experiment to review usability of early strength revelation chemical admixture which is judged in ways effective with premature removal of form about concrete. Use of early strength revelation AE water reducin admixture is apperaing so that strength revelation by early hydration promotions is excellent. The results of being applied proposed work process are that compressive strength are appeared more than 5MPa within 16 hours so that removal of vertical form was possible. the concrete compressive strength satisfied with a more than 2/3 of specified concrete strength for removal of horizontal form are appeared in 42 hours of 27 MPa proportioning strength, in 36 hours of 30, 35 MPa proportioning strength so that the 6 days cycle time of concrete structural frame work is cut by 2 days as shortening delayed period in works of removing slab forms. So construction cost reductions and a construction period shortening are judged so that it is possible.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.347-350
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• 2005

The strength level for removal of lining concrete in tunnel is increased from 2.94MPa to 4.9MPa in 2004. This result in the increase of concrete curing time, and construction time would be delayed. In this study, in order to improve the efficiency of construction cycle and satisfy the strength criterion, a curing method is adopted, which is considering the hydration heat in the lining concrete member. As a result, it is shown that the concrete curing time for form removal is about 20hrs without the adjustment of concrete mix design. And construction cycle time is not changed compared to that before the change of strength criterion.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2005년도 생물공학의 동향(XVI)
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• pp.247-251
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• 2005

This research was performed for developing of biological treatment process of odor gas such as MEK, $H_{2}S$, and toluene, which is generated from the food waste recycling process. To establish the operational conditions of odor gas removal by small-scale biofiltration equipment, it was continuously operated by using toluene as a treating odor object. When the odor treating microorganisms were adhered to fibril form biofilter, high removal efficiency over 93% was obtained by biofilm formation. At 400 ppm of inlet odor gas concentration and 10 sec of retention time, the removal efficiency was 76% and 93% in 1st stage reactor and 2nd stage reactor, respectively. However, the removal efficiency remained over 97% at the operational conditions above 15 sec of retention time.

• 생명과학회지
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• 제9권6호
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• pp.698-703
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• 1999

For the nitrate removal in recirculating aquaculture system, a denitrifying bacterium, Pseudomonas fluorescens, was isolated from municipal sewage and the cells were immobilized in modified-polyvinly alchol (PVA) gel beads. The immobilized cells in both the fixed-and fluidized-bed reactors showed 98% of denitrification efficiency with 6hr HRT, and the removal efficiency of total organic carbon (TOC) was above 90%. Form scanning electron microscopy (SEM) observation, it was known that biofilm formed in fixed-bed reactor was thicker than that formed in fluidized-bed reactor as operation time passed.

• Environmental Engineering Research
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• 제11권2호
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• pp.84-90
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• 2006

UV-catalytic oxidation technique was applied for the treatment of bio-refractory character of the leachate, which is generally present in the form of adsorbable organic halogens (AOX). Destruction of AOX was likely to be governed by pH adjustment, quantitative measurement of oxidants, and the selection of oxidation model type. Peroxide induced degradation ($UV/H_2O_2$) facilitated the chemical oxidation of organic halides in acidic medium, however, the system showed least AOX removal efficiency than the other two systems. Increased dosage of hydrogen peroxide (from 0.5 time to 1.0 time concentration) even did not contribute to a significant increase in the removal rate of AOX. In ozone induced degradation system ($UV/O_3$), alkaline medium (pH 10) favored the removal of AOX and the removal rate was found 11% higher than the rate at pH 3. Since efficiency of the $UV/O_3$ increases with the increase of pH, therefore, more OH-radicals were available for the destruction of organic halides. UV-light with the combination of both ozone and hydrogen peroxide ($UV/H_2O_2$ 0.5 time/$O_3$ 25 mg/min) showed the highest removal rate of AOX and the removal efficiency was found 26% higher than the removal efficiency of $UV/O_3$. The system $UV/H2O_2/O_3$ got the economic preference over the other two systems since lower dose of hydrogen peroxide and relatively shorter reaction time were found enough to get the highest AOX removal rate.