• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.2
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• pp.169-174
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• 2007

In process of reinforced concrete (RC) box structure, the heat of hydration may cause serious thermal cracking. This paper reports results of hydration heat control in mass concrete using the oscillating heat pipe. There were three RC box molds ($1.2m{\times}1.8m{\times}2.4m$) which were different from each other. One was not equipped with pulsating heat pipe. The others were equipped with pulsating heat pipe. All of them were cooled with natural air convection. The pulsating heat pipe was composed of 10 turns of serpentine type copper pipe whose outer and inner diameters were 4 and 2.8 mm respectively. The working fluid was R-22 and charging ratio was 40% by volume. The temperature of the concrete core was approximately $55^{\circ}C$ in the winter without pulsating heat pipe. For a concrete with pulsating heat pipe, however, the temperature difference with the outdoor one reduced up to $12^{\circ}C$. The index figure of crack was varied from 0.75 to 1.38.

• 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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• 2006.05b
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• pp.437-440
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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 results of hydration heat control of mass concrete using the Oscillating Capillary tube Heat Pipe(OCHP). There were the several molds which shows a difference as compared with each other. One was not equipped with OCHP. Other were laid with OCHP, and the other were laid in 100cm, and exposed out 50cm. All of them were cooled with natural air convection. The OCHP was composed of copper pipe(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 $53^{\circ}C$ without OCHP. But the concrete temperature with OCHP was reduced its difference in temperature with the outdoor temperature to $12{\sim}15^{\circ}C$. Finally we saw the index figure of the thermal crack of the structures were varied from 0.6 to 1.6.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.165-166
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• 2012

A thermal stresses by heat of hydration was analyzed according to a change of a pour height in reactor containment building. In case of more than 3.6m pouring height a crack index by heat of hydration analysis resulted in less than 1 because there is not a construction joint of vertical direction and for a self-restraint effect of circumferential section shape. Therefore detailed consideration on a mixture proportion of binder type, quantity in concrete and selection of a form in seasonal air temperature is needed for a control of tensile stress by heat of hydration.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.82-91
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• 2019

In this study, in order to evaluate Hydration Heat Characteristics of mass concrete using ternary blended cement for large underground structures, the analysis considering the temperature history and the thermal characteristics inside the actual structure was performed. The results of the analysis are compared with the measured values to verify the reliability of the analysis and to evaluate the crack resistance performance. As a result of the measured the actual structure temperature, The adiabatic temperature rise coefficients K and ${\alpha}$ of the slab were $35.1^{\circ}C$ and 0.72, respectively, and the wall was analyzed as $29.3^{\circ}C$ and 0.67. The analytical results and the correlation coefficients(r) were 0.95 and 0.98, respectively. As a result of evaluating the crack resistance of slab and wall, the minimum crack index of slab and wall was 1.22 and 1.20, respectively. These results were found to satisfy the site management standards.

• Journal of the Korea Institute of Building Construction
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• v.14 no.5
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• pp.379-388
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• 2014

The purpose of this study is to investigate the effect of capsulated slurry phase change material (PCM) on the thermal crack in mass concrete by experimental work and FEM analysis. In this study, three conditions of samples were prepared for evaluating the level of hydration heat, i.e., a material condition, a cement paste condition and a concrete condition. Also, a compressive strength test was conducted for FEM inverse analysis. Based on the results of the experiment, exothermic function coefficients of concrete with encapsulated slurry PCM were deducted by the inverse analysis. After that, they applied to FEM analysis of the mass scale concrete structures. From the results of this experiment, $31^{\circ}C$ capsulated slurry PCM had no super cooling phenomenon in the material condition. In the cement condition, hydration heat decreased by 34.61J when PCM of 1g was mixed. In the concrete condition, PCM of 6% was deducted as the best level in hydration heat absorption. In FEM inverse analysis, rate coefficient of reaction gradually decreased when PCM mixing ratio increased. But, temperature-rise coefficient increased when PCM mixing ratio exceeded 6%. For the inversed exothermic function coefficients applying to large scale concrete structures, a thermal cracking index increased by 0.05 when PCM of 1% was mixed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.04a
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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.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.157-164
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• 2008

In order to raise efficiency in construction, construction period, construction costs etc. that have been problematic in the methods of hydration heat reduction thus far, this study has developed a new method. The principle of the developed construction method involves the laying of a heat conducting medium such as the heat pipe in the concrete, and through the fast conduction of heat by the heat pipe, the hydration heat occurring within the mass concrete is transferred to the exterior by which the internal hydration heat is reduced. If the study results of the onsite test are summarized, on application of existing hydration heat reduction methods, the highest temperature was reached in about 2$\sim$4 days, but when the heat pipe of this study was used, the period was reduced to within 24 hours. Moreover, when the thermal crack index was calculated with the method using the heat pipe as developed in this study, a value of 1.2 or higher was revealed, which is a level that can restrict the occurrence of cracks. Therefore, when the hydration heat control method using the heat pipe as developed in this study is applied, not only the effects of construction efficiency and reduction in construction period, but also outstanding economical effects can be expected.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.103-113
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• 2017

In the current study, retarding type and standard type admixture design of concrete have been proposed to control the generation of hydration heat for foundation members that use high strengths concrete. Finite element analysis also has been conducted to understand the rational placing heights of concrete. In addition, real-size structures have experimented and their results were compared to the analytical results to evaluate the reducing effect of thermal stress. For a large $6.5m{\times}6.5m{\times}3.5m$ member with retarding and standard type horizontal partition placement of concrete showed the manageable possibility of temperature difference within 25-degree Celcius between the middle and surface portion while the maximum temperature was 77-degree Celcius. Also, temperature cracking index from the finite element analysis appeared to be 1.49 that predicts no formation of cracking due to the effects of temperature. Finally, it appeared that horizontal partition placement of retarding and standard type concrete has the significant effect of reducing the thermal stress that generated by the hydration heat in the high strengths mass concrete.