• International Journal of Concrete Structures and Materials
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• 제10권1호
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• pp.47-60
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• 2016

The objective of this study was to evaluate the capability of different strength-maturity models to account for the effect of the hydration heat on the in-place strength development of high-strength concrete specifically developed for nuclear facility structures under various ambient curing temperatures. To simulate the primary containment-vessel of a nuclear reactor, three 1200-mm-thick wall specimens were prepared and stored under isothermal conditions of approximately $5^{\circ}C$ (cold temperature), $20^{\circ}C$ (reference temperature), and $35^{\circ}C$ (hot temperature). The in situ compressive strengths of the mock-up walls were measured using cores drilled from the walls and compared with strengths estimated from various strength-maturity models considering the internal temperature rise owing to the hydration heat. The test results showed the initial apparent activation energies at the hardening phase were approximately 2 times higher than the apparent activation energies until the final setting. The differences between core strengths and field-cured cylinder strengths became more notable at early ages and with the decrease in the ambient curing temperature. The strength-maturity model proposed by Yang provides better reliability in estimating in situ strength of concrete than that of Kim et al. and Pinto and Schindler.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.385-386
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• 2009

콘크리트 구조물의 온도균열은 타설 초기 시멘트의 수화열에 의한 온도상승 및 강하에 따라 생기는 체적변화가 내부 또는 외부적으로 구속을 받아 발생하는 것으로, 댐과 같은 매스콘크리트 구조물일수록 온도균열 발생가능성은 높아진다. 이 연구는 성덕 다목적 댐의 수화열 해석을 통해 콘크리트 댐의 시공단계에서 타설 간격에 따른 수화열 발생의 비교 및 수화열에 의한 온도균열 발생 유무를 댐의 내외부 온도차가 수렴하는 장기간 동안에서 비교 분석 하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.1163-1168
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• 2000

The method for preventing thermal cracks is necessary in mass concrete structures. So various experiments were carried out for the controls of thermal cracks and we substituted fly ash for a quarter of cement quantity in order to decrease hydration heat. The maximum block size is determined by numerical analysis as well. Hydration heat and thermal stress were measured through various gauges and analysis considering the steps of concrete placement were carried out. It was found from this study that the appropriate block size was able to be determined properly by numerical analysis.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2007년도 춘계학술논문 발표대회
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• pp.33-36
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• 2007

In order to select the optimum mix for the required fluidity and strength of mass concrete which is applied to transfer girder and to choose the optimum curing method depending on circumstances through hydration heat analysis of mass concrete, this study examined slump flow, air content and elapsed variation (0, 30, 60, 90) in unhardened concrete properties and reviewed compressive strength characteristics in hardening properties. And hydration heat analysis results through simulation are as follows; 1) Fluidity changes of unhardened concrete showed no significant difference, and those of elapsed variation also showed no difference but a bit of tendency to increase in comparison with the initial properties. 2) The higher the water-binder ratio was, the lower the compressive strength properties were, and the higher the fly ash replacement rate was, the lower the compressive strength development was. 3) In case of $Fc=40N/mm^2$, the optimum mix was fly ash replacement rate of 15% from water-binder ratio of 33.0%. 4) Hydration heat analysis results showed that in case of bundle cast, concrete temperature profile characteristics around transfer girder was unfavorable, and in case of separate cast, constant curing for at least seven days guaranteed thermal cracking index of 1.2.

• 한국건축시공학회지
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• 제12권4호
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• pp.369-376
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• 2012

본 연구에서는 초기재령에 있어 매스부재를 고려한 고강도콘크리트에 대해 수화발열상승속도를 저감시키기 위한 방안의 일환으로 열흡수성능이 있는 상전이물질을 사용하였다. 또한 수화발열상승속도의 조절에 의한 고강도콘크리트의 자기수축 특성 변화를 분석하고자 하였다. 그 결과, 상전이물질은 시멘트 수화반응을 촉진함으로서 초기재령에 빠른 응결시간과 높은 압축강도 발현을 나타냈다. 또한 수화열 및 수화발열상승속도를 저감시키고, 자기수축량을 감소시키는 결과를 나타내었다. 이를 통해 초기재령의 수화발열상승 속도의 조절에 의해 자기수축량의 저감이 가능하다고 판단된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.25-28
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• 2006

This study investigated pre-mixed cement combined with ordinary portland cement, BF and SF, in order to manufacture cement binder, which is possible to produce 150MPa ultra high strength concrete. The BF used in this study reduces and control hydration heat. It can also improve concrete fluidity, while AP increases hydration product and accelerates reaction of BF. SF has micro filler effect and makes pozzolanic reaction. It also fabricates high density internal organization. This developed pre-mixed cement can reduce hydration heat and increase hydration product. It is possible to fabricate high density organization and to secure homogeneity. The mock-up test of ultra high strength concrete showed excellent dispersibility and workability and indicated compressive strength more than 150MPa at 28 days.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.581-584
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• 2007

The subway concrete box structure can`t establish expansion joint because of animal power delivery of the subway rail. In this case, As increase of structure volume, it is subjected to cause temperature crack. The temperature crack due to the heat of hydration classified a nonstructural crack. but it has a bad effect on durability of concrete structures. especially, in case of a subway concrete box structure, when a water-proof facilities is beaked on an outer-wall, the water leakage occurs through a penetration crack generated from a wall of the concrete structure too. This paper, for the subway concrete box structure, examined a condition of temperature crack occurrence by a heat of hydration concerned external temperature from analysing by a three dimensional finite element method.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 가을 학술발표회 논문집
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• pp.381-386
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• 1994

Recently, the design and construction of massive concrete structures are increased. But, the temperature rise within a large concrete mass make the construction of massive concrete structures be very difficult. Therefore, in Seohae Grand Bridge Project, the field measurement of hydration heat for the massive concrete footings(11$\times$22$\times$4m) was carried out. It was shown to be possible to construct the massive concrete footing successfully by application of pipe cooling system. And the measurement results showed that standard code for concrete practice was very conservative.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 가을 학술논문 발표대회
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• pp.171-172
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• 2022

This study aims to develop the hydration heat reducing material (powder type) to lower the heat of hydration of mass members in the extremely hot weather condition. In this study, we applied the developed material to the concrete that used two kinds of binders with cement and evaluate the concrete properties with it.

• Computers and Concrete
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• 제13권1호
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• pp.97-115
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• 2014

Silica fume is a by-product of induction arc furnaces and has long been used as a mineral admixture to produce high-strength, high-performance concrete. Due to the pozzolanic reaction between calcium hydroxide and silica fume, compared with that of Portland cement, the hydration of concrete containing silica fume is much more complex. In this paper, by considering the production of calcium hydroxide in cement hydration and its consumption in the pozzolanic reaction, a numerical model is proposed to simulate the hydration of concrete containing silica fume. The heat evolution rate of silica fume concrete is determined from the contribution of cement hydration and the pozzolanic reaction. Furthermore, the temperature distribution and temperature history in hardening blended concrete are evaluated based on the degree of hydration of the cement and the mineral admixtures. The proposed model is verified through experimental data on concrete with different water-to-cement ratios and mineral admixture substitution ratios.