• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.345-348
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• 2005

This paper presents the result of adiabetic temperature rise and fundamental properties of concrete combining admixtures. According to results, difference of setting time with I5.5hours is observed between S-P and R-F30 mixture. Based on the adiabetic temperature rise test, 8$^{circ}C$of heat producted occurs between E-P and R-F30 mixture. is applied to estimate the temperature rising under adiabetic curing condition, which exhibits closer consistency with tested value. The function mentioned above can account for the effect of dormant period in hydration process at early stage on hydration heat production. It reveals that the consideration of placing layer based on the mixture adjustment(E-P mixture at top layer and R-F30 mixture at bottom layer) in mass concreting will contribute to reduce hydration heat as well as alleviate tensile stress discrepancy between placing layer.

• Structural Engineering and Mechanics
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• 제74권6호
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• pp.747-756
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• 2020

High-strength concrete (HSC) generally is made with high amount of cement which may release large amount of hydration heat at early age. The hydration heat will increase the internal temperature of slab and may cause potential cracking. In this study, slab specimens with a dimension of 600 × 600 × 100 mm were cast with concrete incorporating silica fume for test. The thermistors were embedded in the slabs therein to investigate the interior temperature development. The test variables include water-to-binder ratio (0.25, 0.35, 0.40), the cement replacement ratio of silica fume (RSF; 5 %, 10 %, 15 %) and fly ash (RFA; 10 %, 20 %, 30 %). Test results show that reducing the W/B ratio of HSC will enhance the temperature of first heat peak by hydration. The increase of W/B decrease the appearance time of second heat peak, but increase the corresponding maximum temperature. Increase the RSF or decrease the RFA may decrease the appearance time of second heat peak and increase the maximum central temperature of slab. HSC slab with the range of W/B ratio of 0.25 to 0.40 may occur cracking within 4 hours after casting. Reducing W/B may lead to intensive cracking damage, such as more crack number, and larger crack width and length.

• Rapid Communication in Photoscience
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• 제4권3호
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• pp.54-58
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• 2015

Under the condition of femtosecond impulsive nonlinear optical irradiation, the bright and narrowed blue emission of silicon nanocrystal was observed. This synthetic method produced very small (~ 4 nm) oxide-capped silicon nanocrystal having probably ultra small emitting core (~ 1 nm) inferred from luminescence. By controlling the stirring condition, very high efficiencies of luminescence ( 4 fold higher) were obtained compared with the other conventional femtosecond laser fragmentation methods, which was attributed to the differences in hydration shell structure during the femtosecond laser induced irreversible phase transition reaction. When we properly adjusted the irradiation times of the white light continuum and stirring condition, very homogeneous luminescent silicon nanocrystal bands having relatively sharp lineshape were obtained, which can be attributable to the luminescent core site isolated and free from the surface defects.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.293-296
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• 2003

The purpose of this study is to examine the effect of aluminium sulfate on setting time and compressive strength of cement mortar as focused on formation of ettringite by the reaction between aluminium sulfate and calcium hydrate. The specific parameter was the addition ratio of aluminium sulfate to cement mortar. After specimens made by admixing aluminium of 0~7% by weight of cement, respectively, to cement mixtures, the experimental items such as setting time, compressive strength and heat of hydration in this study were carried out. As a result of this study, it is possible that aluminium sulfate could be added into cement mixture from a standpoint of increasing early compressive strength as considering the setting time and heat of hydration.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.29-30
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• 2020

In this study, as part of the foundation for advancing the material compounding aspect to reduce hydration heat cracks in the mat foundation on which the mass concrete is constructed, the degree of concrete varieties of cement is used. The setting time was measured and comparative analysis was performed. Results It was confirmed that the concrete using LHC was more effective than the concrete using OPC in reducing the use of SP, the calorific value of the concrete was low, and it was more effective in preventing cracks. It is also terminated after 10 hours and it is determined that the use of LHC can reduce the cracks caused by the heat of hydration of the mat foundation.

• 한국구조물진단유지관리공학회 논문집
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• 제26권4호
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• pp.48-56
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• 2022

시멘트계 재료의 응결시간 제어는 초기 콘크리트 성능 확보를 위한 중요한 평가 요소 중 하나이다. 최근 평균 기온 상승으로 특정 수화물 생성 억제 및 응결시간 제어를 위한 지연제의 사용이 권장되고 있다. 비카트 침 등 관입저항 측정 시험법의 한계를 극복하기 위해 응결시점 평가를 위한 다양한 비파괴 평가 기법이 제안되고 있지만, 지연제 사용에 따른 비파괴 평가법 사용 가능성 확보를 위해서는 여전히 실험적 연구 수행이 요구되고 있다. 본 연구에서는 타타르산 지연제를 사용하여 시멘트 페이스트의 응결 지연을 유도하고, 비카트 침 시험과 함께 전기비저항과 초음파 속도 모니터링을 수행하였다. 두 비파괴 측정 결과의 상승시점 결정을 통해 시멘트 페이스트의 응결시점을 평가하고, 비카트 침 측정을 통한 초결 및 종결 시점과의 분석으로 지연제 사용에 따른 응결 지연 현상 평가 가능성을 확인하였다. 또한 전기비저항 상승시점에 대한 X선 회절 분석을 통해 타타르산 지연제 사용에 따른 수화반응 변화를 측정하고 전기비저항 측정의 응결 지연 평가에 영향을 주는 주요 수화물을 확인하였다.

• 한국세라믹학회지
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• 제44권1호
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• pp.43-51
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• 2007

Fluidity, setting time, hydration heat, bond water ratio, compressive strength, SEM and BET of OPC were measured by adding 1.0 wt% KCl and replacing 20 wt% mineral admixture in order to examine effects of blast furnace slag (BFS), limestone powder (LSP), and fly ash (FA) on fluidity and strength development of the cement contained much chloride. In general, the cement contained much chloride was high in heat of hydration, short in its setting time, low in its fluidity and low in its strength at 28 days due to the rapid hydration in its initial stage. As a result of the experiment, it has been demonstrated that fluidity became improved but the compressive strength at 28 days was decreased as replaced LSP to the cement contained much chloride. the fluidity and compressive strength at 28 days was improved as replaced BFS, the initial compressive strength development was improved due to the activation of initial reaction by KCl. Fluidity, initial compressive strength and late compressive strength at 28 days of cement contained much chloride replaced 5 wt% LSP and 15 wt% BFS concurrently was better than OPC, but the hydration heat was lower.

• 콘크리트학회논문집
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• 제27권3호
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• pp.265-272
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• 2015

본 연구에서는 매스콘크리트의 높은 수화열을 제어하기 위하여 결정핵 (C-S-H)와 지연제(포도당)를 동시 사용하여 최대 수화온도를 낮추면서, 응결지연효과를 상쇄시키는 방법이 제시되었다. 이를 위하여 시멘트 페이스트의 수화온도를 측정하고, C-S-H와 포도당의 동시 사용이 시멘트 모르타르의 응결시간 및 압축강도에 미치는 영향을 조사하였다. 실험결과에 따르면. 칼슘실리케이트 수화물과 포도당을 동시 사용할 경우 최대 수화온도를 저감하면서도 최대수화온도에 도달하는 시간을 줄일 수 있음을 확인하였다. 또한 C-S-H와 포도당의 동시 사용은 시멘트 모르타르의 28일 압축강도에는 큰 영향을 미치지 않는 것으로 나타나, 이러한 방법이 매스콘크리트의 수화열 조절에 효과적인 대안이 될 수 있음을 알 수 있었다.

• 한국식품과학회지
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• 제20권2호
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• pp.256-262
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• 1988

우리나라 콩 중 장려품종(봉의) 및 재래종 품종(KW12, KLS-77005-1 및 B-102)의 수분흡수 특성을 조사하였다. 콩을 $4-98^{\circ}C$에서 침지하였을 때 $40^{\circ}C$ 이하에서는 침지시간 10시간 동안에 평형상태에 도달하지 않았으나, $60^{\circ}C$이상에서는 3시간정도에서 평형상태에 도달하였다. 콩이 수분흡수속도는 102-B>봉의>KLS-77005-1>KW-12의 순이었다. 콩의 수분증가량은 침지온도에 상관없이 침지시간의 평방근과 직선적인 관계를 보였으며, 수분흡수의 기본기작은 확산현상에 기인하였다. 침지온도 $4-20^{\circ}C$에서의 흡수의 활성화에너지 값은 2,0-2.7kcal/mole, 침지온도 $20-60^{\circ}C$에서는 6.4-6.6kcal/mole이었다. 콩을 $4-60^{\circ}C$에 침지하는 동안 일정한 수분함량에 도달하는 침지시간의 대수값과 침지온도와는 직선적인 관계를 보였으며, 콩의 수화도가 증가할수록 z-값은 감소하였다. 수분함량 50%에 도달하는 z-값은 시료콩 모두 $50^{\circ}C$정도 이었다.

• 대한건축학회논문집:구조계
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• 제35권10호
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• pp.207-215
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• 2019

The aim of the research is analyzing the simple adiabatic temperature rising properties and the heat of hydration based on different placing timing of the mass concrete depending on various replacing ratios of blast furnace slag to comparative analyze the thermal cracking index and cracking possibility. As a result from the experiment, a suggested adiabatic temperature rising equation based on various blast furnace slag replacing ratios can be provide favorable correlation with over 0.99 of $R^2$ value by applying the initial induction period. With this relationship, more accurate prediction of the amount of the hydration heat rising and heating timing, and it is known that there is an approximately $13.1^{\circ}C$ of gap between plain concrete without blast furnace slag and concrete with 80 % of replacing blast furnace slag. To control the setting time and heat rising gap, the mix designs between top and bottom concrete casts were changed 15 cases, and D, E, H, I, and L models of controlling the heat of hydration showed 41.23 to $46.88^{\circ}C$ of core temperature and 0.98 to 1.27 of thermal cracking index. Therefore the cracking possibility was 15 to 52 % of favorable results of possibly controlling both the cracking due to the internal and external retainment and concrete temperature at early age.