• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.6
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• pp.1705-1710
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• 2008

In this paper, a program for simulating hydration heat and stresses was developed. And an effective methods were proposed for reduction of hydration heat stresses using flyash and steel fiber. It was shown that flyash replacement made reduction of peak temperature due to hydration heat. However, the effectiveness of reduction of tensile stress was not as good as it of peak temperature. Not only peak temperature but also tensile stress were reduced by the addition of steel fiber.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.101-102
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• 2012

In this study, it was evaluated about hydration heat reduction under hot weather condition. Placement temperature set 25℃ and 35℃, For hydration heat reduction was applied such as FA and BFS. As a results, mixture of BFS70% is the most effective hydration temperature reduction.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.140-143
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• 2004

Heat of hydration of concrete under different curing temperatures can be characterized with knowledge of the thermal activity, the heat rate at the reference temperature, and the total heat of hydration of the mixture. The so-called multi-component hydration model incorporates the effect of following variables: cement chemical composition, cement fineness, secondary cementitious powders, mixture proportions, and concrete properties. However, the model does not consider the use of silica fume as a secondary cementitious powder. Therefore, the model that quantifies the heat of hydration due to the use of silica fume is needed. In this thesis, the effects of silica fume on heat of hydration are evaluated and the influence on the heat of hydration are also quantified to be included in the model, so that the analysis using modified multi-component hydration model for silica fume concrete provides more accurate results than normal concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.481-484
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• 2008

The temperature crack of concrete structure is caused by the phenomenon which the concrete volume is restricted in the inside or outside part due th the temperature variations induced by the hydration heat of cement. And mass concrete structures are weak in temperature crack. Seongdeok multi-purpose dam is gravity dam which is being constructed in Cheongsong-gun, Gyeonsangbuk-do. Upstream cofferdam was constructed to examine the temperature crack due to hydration heat and to decide the height of placement. Therefore this study performed the hydration heat analysis of Seongdeok upstream coffer dam to analyze the hydration heat according to different height of placement and to compare with measured results.

• Smart Structures and Systems
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• v.12 no.1
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• pp.41-54
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• 2013

Concrete is known as a heterogeneous product which is composed of complex chemical composition and reaction. The development of concrete thermal effect during early age is critical on its future structural health and long term durability. When cement is mixed with water, the exothermic chemical reaction generates hydration heat, which raises the temperature within the concrete. Consequently, cracking may occur if the concrete temperature rises too high or if there is a large temperature difference between the interior and the exterior of concrete structures during early age hydration. This paper describes the contribution of novel Fabry-Perot (FP) fiber optic temperature sensors to investigate the thermal effects of concrete hydration process. Concrete specimens were manufactured under various water-to-cement (w/c) ratios from 0.40 to 0.60. During the first 24 hours of concreting, two FP fiber optic temperature sensors were inserted into concrete specimens with the protection of copper tubing to monitor the surface and core temperature change. The experimental results revealed effects of w/c ratios on surface and core temperature developments during early age hydration, as well as demonstrating that FP fiber optic sensors are capable of capturing temperature variation in the concrete with reliable performance. Temperature profiles are used for calculating the apparent activation energy ($E_a$) and the heat of hydration (H(t)) of concrete, which can help us to better understand cement hydration.

• Journal of the Korea Computer Industry Society
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• v.9 no.3
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• pp.99-104
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• 2008

The thermal stresses due to hydration heat in massive concrete structures are affected by ambient temperature and placing concrete temperature. It is needed to predict the thermal stresses considering ambient temperature and placing concrete temperature. In this study, hydration heat analyses of coping were carried out. After the maximum tensile stress was occurred at 2,75 days the crack index was increased. Therefore the possibility of crack occurrence was rare. The possibility of crack occurrence can be reduced by placing concrete temperature drop. Therefore some method to drop the placing concrete temperature may be effective to reduce the possibility of crack occurrence.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.413-416
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• 2006

In process of the mass concrete structure, the heat of hydration may cause serious thermal cracking. In order to eliminate hydration heat of mass concrete, this paper reports results of hydration heat control of mass concrete using the Oscillating Capillary tube Heat Pipe(OCHP). There were the several RC box molds which shows a difference as compared with each other. One was not equipped with OCHP. The others were equipped with OCHP. All of them were cooled with natural air convection. The OCHP was composed of copper pipe with 11 turns(outer diameter : 4mm, inner diameter : 2.8mm) and heat type was non-looped type. The working fluid was R-22 and its charging ratio was 40% by volume. The core of the concrete temperature was approximately $55^{\circ}C$ in the winter without OCHP. But the concrete temperature with OCHP was reduced its difference in temperature with the outdoor temperature to $12^{\circ}C$. Finally we saw the index figure of the thermal crack of the structures were varied from 0.75 to 1.47.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.915-918
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• 2008

Hydration heat and autogenous shrinkage are generated essentially by the same hydration. Many researchers have studied the close relationship between hydration temperature and autogenous shrinkage but hardly any research has been undertaken to explain the specific numerical relation. In this study, early age properties of hydration heat and autogenous shrinkage of specimen whose section size was changed were analyzed, and relationship between hydration heat and autogenous shrinkage was investigated. In the results of the study, inner temperature and autogenous shrinkage increased as the section size increased. And rise and rise ratio of hydration temperature and autogenous shrinkage in hydration heating section and autogenous shrinking section are increased too. Temperature rise and autogenous shrinkage rise increased respectively, as hydration heating velocity and autogenous shrinking velocity increased. And autogenous shrinkage rise and autogenous shrinking velocity increased as hydration heating velocity increased.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.55-57
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• 2012

In this study, the field applicability on reducing the heat of hydration of mass concrete by using the hydration heat difference method is analyzed with the following summary. As a result of applying the hydration heat difference method by using low heating combination, the temperature difference between the central part and the surface part of mass material was reduced, and as a result of visual observation, there was no showing of cracks by the hydration heat on the upper surface part. Therefore, the cracking index of the field to apply this method was shown to be approximately 1.57 with very little crack occurrence probability of less than 3%.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.249-252
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• 2008

In recent large-scale structures, as mass concrete type structure is frequently applied to the building, temperature crack due to hydration heat needs to be considered. Since a volume change is internally or externally restricted in a mold after placing concrete, temperature crack of mass concrete takes place. By this reason, the reduction method to control this crack is required. In this study, low heat mixture and hydration heat difference is used to execute the analysis of hydration heat, considering the changes of heat transfer coefficient according to curing conditions and block placement of mass concrete. For the analytical modelling, original portland cement and concrete of low heat mixture are placed in the upper and lower payer, respectively. A convection boundary condition is fixed because mass concrete of block placement is characterized by the difference of mold form and curing condition. Through the analysis results considering the changes of low heat mixture, block placement, and heat transfer coefficient, we check out the temperature and stress distribution and analyze the temperature crack reduction effect.