• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.422-429
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• 1997

Thermal stress induced by hydration heat may produce cracks in mass concrete structure, which can result in structural problems as well as bad appearance. To minimize crack occurrence in massive structural, thus, the study put an emphasis on the determination of optimized lift height and block size. In the parametric study different sizes and lift heights were used to measure the magnitudes of hydration heat and thermal stresses for 3 different types of concrete fabricated with 1 pure cement and 2 blended Portland cements. As a result of analysis. it was found that magnitude of hydration heat and the occurrence of thermal cracks depend on the restriction conditions and material characteristics, especially adiabatic material parameters. It was also found that optimized lift height and block size can be determined from an appropriate combination of the degree of inner and outer structural restrictions.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.70-71
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• 2019

Glass fiber reinforced concrete (GFRC) is very suitable as a material for free-form concrete panels (FCPs) because of its lightweight, strong, moldable, durable and sustainable properties. GFRC is superior in construction and maintenance compared with materials such as steel, aluminium, titanium, glass and plastic, and is advantageous in cost. However, GFRC is being produced by skilled craftsmen, and still lacks the technology to economically produce high quality FCPs. Currently, there is a technology to automatically and accurately produce FCPs. However, the developed technology can not be applied to the field with simple production technology without production line for mass production. To solve this problem, the purpose of this study is a basic study of production system development of free-form concrete panels. This study introduces the developed FCPs production technology and builds FCP production system for mass production. The results of this study will be used as basic data for the commercial production of FCPs in the future.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.175-176
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• 2020

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.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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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.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.25-26
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• 2015

In this study, we test the 3 properties low hydrated heat as binder, and also utilized the hydrated heat disparity construction method to decrease the cracks of the mass concrete caused by hydrated heat. The result showed by using the two methods narrowly decreased the cracks. And we ensured that during the mass concrete pouring, the cracks caused by hydrated heat could be reduced by utilizing the new construction method.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.158-159
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• 2022

This study analyzed the temperature stress through mixtures mass concrete hydration heat analysis according to the replacement rates of FAC and CGS. As a result of the analysis, it was possible to confirm the effect of reducing hydration heat when CGS is substituted for the low heat mixture of mass concrete. However, the stress of the FAC+CGS combination exceeded the tensile stress. It is believed that it is necessary to apply the insulating sheet of the surface part and reduce the unit weight of cement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.235-236
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• 2021

This study evaluated temperature distribution through adiabatic temperature rising test and hydration heat Analysis as a performance verification to utilize CGS as a hydration heat reduction material for mass concrete when replacing it with fine aggregate. According to the analysis, the temperature difference between the center and the surface was the highest at about 30℃, followed by the CGS 50% at 26℃ and the low heat combiner FA 30% at 23℃.

• Magazine of the Korea Concrete Institute
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• v.6 no.5
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• pp.203-212
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• 1994

The setting and hardening of concrete is accompanied by nonlinear temperature distribution caused by developing heat of cement hydration. This leads to tensile stresses that may exceed the strength of the young concrete, and cracks occur. In this present study, the heat of hydration characteristics are obtained from a study in which insulated concrete cubes were tested. Based on test results, concrete heat of hydration characteristics according to unit weight cement and flyash replacement quantity are determined, then employed in a numerical temperature analysis that consider both environmental interaction and concreting phases. The numerical results are performed by ADINA - T. The analytical results are in good agreement with experimental data.

• Computers and Concrete
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• v.17 no.2
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• pp.173-188
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• 2016

Generally, thermal stress induced by hydration heat causes cracking in mass concrete structures, requiring a thorough control during the construction. The prediction of the thermal stress is currently undertaken by means of numerical analysis despite its lack of reliability due to the properties of concrete varying over time. In this paper, a method for the prediction of thermal stress in concrete structures by adjusting thermal stress measured by a thermal stress device according to the degree of restraint is proposed to improve the prediction accuracy. The ratio of stress in concrete structures to stress under complete restraint is used as the degree of restraint. To consider the history of the degree of restraint, incremental stress is predicted by comparing the degree of restraint and the incremental stress obtained by the thermal stress device. Furthermore, the thermal stresses of wall and foundation predicted by the proposed method are compared to those obtained by numerical analysis. The thermal stresses obtained by the proposed method are similar to those obtained by the analysis for structures with internally as well as externally strong restraint. It is therefore concluded that the prediction of thermal stress for concrete structures with various boundary conditions using the proposed method is suggested to be accurate.

• Nuclear Engineering and Technology
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• v.30 no.6
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• pp.568-580
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• 1998

A sodium-concrete reaction facility with a test chamber of 0.226㎥($\Phi$0.6m$\times$H0.8m) was constructed to carry out experiments of sodium-concrete reaction which might take place in sodium metal fast-breeder reactor Utilizing this facility, several experiments were conducted to closely examine the characteristics of sodium-concrete reactions under different conditions : Sodium mass : 100, 250g ; Sodium temperature : 450, 550, $650^{\circ}C$ ; Concrete age = 30, 45, 50, 90days. Our experiments show that the amount of the H2 generated by sodium-concrete reaction has increased up to its flammable range as the amount of spilled sodium and its temperature have increased. The maximum hydrogen concentration was 31mo1% at the concrete age of 30days, sodium temperature : 55$0^{\circ}C$, and sodium mass : 250g. The major components of sodium-concrete reaction products were also determined as Na$_2$SiO$_3$ and NaAlO$_2$.