• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1041-1044
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• 2008

The addition of chemical inert filler in blended cement, such as limestone or chemical inert silica fume, will produce a physical effect on cement hydration. Due to the high surface area of inert filler in the mixtures, it provides sites for the nucleation and growth of hydration products, thus improving the hydration rate of cement compounds and consequently increasing the strength at early age. This paper proposes a model of hydration of Portland cement blended with chemical inert filler. This model considers the influence of water to cement ratio, cement particle size, cement composition and addition of chemical inert filler on hydration. The heat evolution, degree of hydration and porosity are obtained as accompanied results in hydration process. The prediction results agree well with experiment results.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.425-428
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• 2006

The bigger of concrete strctures by a construct technique improvement, and the increase of the cement quantity which is caused by with use of the high-strength concrete for the load-carrying-capacity and a durability cause temperature cracks by a heat of hydration. 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 strucuture, the use of blended cement, the temperature of air and concrete, control joint, was considered and analysed by a three dimensional finite element method.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.705-708
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• 2006

The bigger of concrete structures by a construct technique improvement, and the increase of the cement quantity which is caused by with use of the high-strength concrete for the load-carrying-capacity and a durability cause temperature cracks by a heat of hydration. 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, which is located in chloride attack region, the use of blended cement, the temperature of air and concrete, was considered and analysed by a three dimensional finite element method.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.29-34
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• 2002

The heat of hydration of cement causes the internal temperature rise at early age, paticular in massive concrete structures. As the results of the temperature rise and restraint condition, the thermal stress may induce cracks in concrete. The prediction of the thermal stress is important in design and construction stages in order to control the cracks in mass concrete. It is poor economy to analysis for prediction of the thermal stress on each design or construction. In this study, the hydration heat and thermal stress analysis is performed by ABAQUS program, as a results of thermal analysis, the formula of size-placing depth relationship is proposed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2001.11a
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• pp.52-57
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• 2001

In order to control hydration heat in mass concrete, pipe cooling method has been widely used. The pipe cooling method leads to the decrease of curing period by lagging materials as well as the decrease of temperature difference between center and surface of mass concrete member, There are two methods in the pipe cooling system, which are open loop system and closed loop system. However open loop pipe cooling system cannot be applied to the mass concrete structures when cooling water supply is difficult. To control hydration heat of high strength mass foundation in the central area of city, closed loop pipe cooling system was developed to solve the cooling water supply. This paper reports the performance results of hydration heat control with closed loop pipe cooling system.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.595-598
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• 2005

Recently, owing to the development of industry and the improvement of building techniques, the concrete structure is becoming larger and higher. In hardening these large concrete, the heat of hydration gives rise to considerable thermal stress depending on the size and environmental condition of concrete, which might cause thermal cracking. Especially, the crack may cause severe damage to the safety and the durability of concrete structure. This study is investigated the thermal properties of concrete according to several binder conditions, such as OPC, Belite rich cement(BRC), slag cement(SC), blast furnace slag (BFS) added cement, fly ash added cement and BFS-fly ash added cement. As a result of this study, the concrete made with BRC, fly ash($25\%$) added cement and BFS($35\%$)-fly ash($15\%$) added cement gets superior effect in the control of heat hydration.

• 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 Korea Concrete Institute Conference
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• 2005.05b
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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.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.693-696
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• 2006

In massive hardening concrete structures, early age thermal cracking due to the heat of hydration may occur. There are many massive structures in Incheon bridge project and they have to be carefully treated to prevent thermal cracking. In this paper, an example of analyzed and measured results of hydration heat of pile caps in the Incheon bridge project was represented. Finite element simulations were carried out before casting and curing method was determined using the analyzed result. Sensors were installed before casting and temperature and strain of concrete was measured during curing. Gathered data were compared with the analyzed data and selected control method to prevent cracking was verified. Analyzed result gave good agreement and very few cracking could be found.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.421-424
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• 2006

In massive hardening concrete structures, early age thermal cracking due to the heat of hydration may occur. There are many massive structures in Incheon bridge project and they have to be carefully treated to prevent thermal cracking. In this paper, an example of analyzed and measured results of hydration heat of pile caps in the Incheon bridge project was represented. Finite element simulations were carried out before casting and curing method was determined using the analyzed result. Sensors were installed before casting and temperature and strain of concrete was measured during curing. Gathered data were compared with the analyzed data and selected control method to prevent cracking was verified. Analyzed result gave good agreement and very few cracking could be found.