• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.189-196
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• 2020

When concrete member become large like in high rise buildings, hydration heat makes temperature difference inside and outside and cause cracks. The method of using latent heat material as heat reducer could be more accessible, usable and efficient than other methods. Therefore, many studies using PCM as heat reducer are being conducted. Since heat reducer have different reacting temperature, they may be affected by environmental factors like ambient and concrete mixing temperature but studies issuing this are insignificant. Therefore, this paper attempt to evaluate the hydration heat characteristics and quality of concrete using strontium-based PCM under hot weather conditions. As a result, when the strontium-based hydration heat reducer was mixed 3wt.% and 5wt.% in hot weather condition, hydration heat speed and heating rate could be reduced by 8%, 21%, and 75, 85 minutes compared to OPC, respectively. This is considered to be the phase change reaction is relatively promoted when the temperature is high and cause improve performance than room condition result. Later, comparing the efficiency of other types of P.C.M in hot weather condition, and conduct detailed reviews on the strength development in long-term age.

• 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.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.257-258
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• 2010

The research was investigated the hydration heat and the fundamental properties of concrete using high volume mineral admixture for reducing hydration heat temperature. The results were that compared to OPC 100%, the dosage of superpasticizer agents was decreased about 50% degree at the same flowing, and the compressive strength was developed about 95% degree. Also, temperature rise of heat of hydration was decreased by 36~48% comparing to OPC and FA25, and it is estimated that it will have a large effect to hydration heat reduction of mass concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.363-368
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• 2001

Abutments in Kumdang bridge are massive concrete structures of which total height is l0m, length is 30m, and width is 7m. Therefore, there is every probability that early age thermal cracking such as hydration heat occur. We measure heat of hydration, strains of rebar, and stresses of concrete abutment during construction. Using analysis of measuring data, we examine thermal stresses, and make use of results as method which control thermal cracking. Finally, we develope thermal stress analysis program which have pre/post processor to be easy of accessing and the usefulness of that is estimated through comparison of results.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.587-590
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• 2005

This study investigates the efficient construction scheme of the immersed tunnel focusing on the hydration heat. In this respect, some alternatives in curing, temperature condition and removing of the forms are compared together to meet the required criteria. It is addressed that the strict construction stage analysis considering the placing scheme of concrete is one of the key factors to trace the realistic structural behavior for the hydration heat.

• 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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• 2004.05a
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• pp.11-14
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• 2004

In this paper, field application of mass concrete using setting time difference of super retarding agent is reported to reduce hydration heat of concrete placed at newly constructed apartment house in Busan. Horizontal placing lift is applied. According to test results. slump and air content meets the requirement of target values. For compressive strength, it exceeds the nominal strength ordered by the costumer. Compressive strength of concrete cured in place is achieved more than the values of nominal strength at l4days. For temperature history, maximum temperature of center at top section shows 58.5$^{\circ}C$, and at bottom section, 62.6$^{\circ}C$. According to naked eye's investigation, no hydration heat crack is observed at the surface of concrete.

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.483-488
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• 2015

Blast furnace slag(BFS) is well known for its hardening mechanism in ordinary Portland cement with alkali activation due to its latent hydraulic property. The possibility of using calcium compound as activator for BFS has been investigated in this study. The hydration properties of calcium compound activated BFS binders were explored using heat of hydration, powder X-ray diffraction and compressive strength testing. Heat of hydration results indicate that the hydration heat of BFS is lower than OPC paste by about 50%. And ettringite as hydration product was formed continuously as the calcium sulfate was decreased. The maximum compressive strength of hardened BFS mortar at 28 days is confirmed to be 83% as compared with hardened OPC mortar.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.380-386
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• 1996

This paper presents the history of heat hydration and the core strength of underwater non-segregation concrete. Three types of cements including Type I, Type V and low-heat cement have been used to make the mass specimens for measurement of heat of hydration and also for coring. Two environments of ambient and underwater conditions have been accounted for the comparison of producing the heat of hydration and for the assessment of core strength in respect to the test specimens made under normal practice.

• Journal of the Korean Ceramic Society
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• v.43 no.9 s.292
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• pp.537-543
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• 2006

Length change, hydration heat, setting time and compressive strength of OPC were measured by adding KCl and replacing limestone powder so as to examine the influence of limestone powder on hydration of the OPC contained much chloride. In general, the chloride modified cement was high in heat of hydration, short in its setting time, low in its fluidity and low in its strength at 28 days due to the sudden hydration in its initial stage. As a result of the experiment, it has been demonstrated that heat of hydration, became low as one replaced limestone powder to the chloride modified cement, and the fluidity and shrinkage rate of mortar decreased without change in setting time; furthermore, the compressive strength at 28 days was improved.