• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.527-532
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• 2001

The crack of concrete induced by a temperature rise in early age concrete due to the heat of ration of cement is a serious problem for massive or high strength concrete structures. However, re is still no reasonable equations for the prediction of the temperature rising. On this study, the prediction equations of the heat of hydration of different types of binder are pained from the adiabatic temperature rise test, and compared with the results from different nations to obtain the best approximated equation. The strengths of concrete of which specimens were placed in the same chamber for the adiabatic to were compared with those under standard curing.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 봄 학술발표회 논문집
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• pp.209-214
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• 1994

The heat of hydration of cement causes the intemal temperature rise at early age, particulay in massive concrete structures. As the results of the temperature rise and restraint condition, the thermal stress amy induce cracks in concrete. The prediction of the thermal stress is very important in design and consturction slages in order to control the cracks in mass concrete. In this study, the temperature rise of high strength concrete due to the heat of hydration is investigated. Test variables are type and content of binder. As the results, the temperature rise is imcreased with increasing cement content. However, the increament is decreased in higher cement comtnet range. Fly ash is effictive in the reduction of hydration heat.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.641-646
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• 2001

In early-age concrete, volumetric deformations due to thermal expansion and moisture transfer are restrained by various boundary conditions, and then restraint stresses occur in proportion to developed stiffness. With increase of the age, these stresses are gradually relieved by significant relaxation behavior of early-age concrete. Therefore, it is necessary to consider the stress relaxation in order to analyze the behavior of early-age concrete more accurately. In this paper, we propose a unified algorithm which combines a relaxation model with hydration model, heat conduction model, micropore structure formation model, moisture diffusion model and mechanical properties development model and develop a finite element program based on the algorithm. The program is applied to evaluate stress development if a temperature-stress test machine (TSTM) specimen and a massive concrete structure, and then validity of the program is discussed and evaluated.

• Architectural research
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• 제15권1호
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• pp.53-58
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• 2013

High strength concrete is being used increasingly in mass structure projects. The purpose of this study is to investigate the influence of temperature during mixing, placing and curing on the strength development, hydration products and pore structures of high strength concrete in mass structures. The experiments were conducted with two different model walls, viz.: 1.5 m and 0.3 m under typical summer and winter weather conditions. The final part of this study deal with the clarification of the relationship between the long-term strength loss and the microstructure of the high strength concrete at high temperatures. Test results indicated that high elevated temperatures in mass concrete structures significantly accelerate the strength development of concrete at the early ages, while the long-term strength development is decreased. The long-term strength loss is caused by the decomposition of ettringite and increased the total porosity and amount of small pores.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.299-304
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• 1999

Cracking of concrete is one of the main issues of structural design next to ensuring the load-bearing capacity. Thermal cracking is a recurring concern in the production of concrete structures in particular when large, massive structures are considered. Thremal stresses arise from the differential temperature distribution either within s sturcture or between newly cast sectons and adjoining older parts. There are many different methods of reducing thermal stresses. A method often used for reducing temperature within a structure, is to cool the inner core with embedded cooling pipes. In this study, finite element method is employed for thermal analysis of concrete structures. To calculate water temperature variation in pipe, the conservation of thermal energy in internal flow was adopted. The cooling effect of pipe cooling is studied with several factors like convective coefficient, water temperature, concrete heat characteristics

• 콘크리트학회논문집
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• 제12권3호
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• pp.31-37
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• 2000

When a crack is produced in a concrete structure, a micro crack zone of fracture process zone (FPZ) appears at the crack tip. To investigate the behaviour of this the micro crack zone, nonlinear fracture mechanics (NLFM) must be applied. However, when a massive concrete structure such as a concrete gravity dam is considered, the micro crack zone can be neglected and the structure can be assumed to have linear elastic fracture mechanics (LEFM) behaviour. This study is divided into two main topics : (1) Calculating stress intensity factor (SIF) at the crack tip by surface integral method and (2) Investigating the propagation of the initial crack. If the initial crack propagates, the angle of the propagation is calculated by using maximum circumferential tensile strength theory. This study, also, contains the effects of body forces and water pressures on the crack face.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.329-333
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• 1995

The usual methods for the temperature control of mass-concrete structures include the use of low-heat cement, pre-cooling, or pipe-cooling. In order to control the heat of hydration of mass-concrete structures such as massive pier or anchor block, and mat foundation, the pipe cooling method is widely acceptable for pratical use. In this paper, method of analysis using the Finite Element Method was applied to analyze the heat exchange on the field of three dimensional thermal conduction. The result of analysis Well agreed with experimentally measurement data by "KUMATANI". The method of this analysis will be used widely to control the heat of hydration by the pipe cooling in mass-concrete.-concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.709-712
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• 2006

It is necessary to develop a new technology for controling thermal cracking by hydration heat according to the increase construction of massive concrete structures, high strength concrete and early strength concrete. Therefore, it was investigated the characteristics of hydration heat generation of low heat concrete using hydration heat reducing admixtures in this study. To investigate the performance of hydration heat reducing admixtures, it was evaluated hydration heat according to the kind and replacement ratio of phase change material series I, II and the way of using hydration heat reducing admixtures in series III.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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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.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.463-468
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• 1999

The slurry wall of Inchon LNG receiving terminal tank will be planned the super flowing concrete having properties of high strength (required strength 520kg/$\textrm{cm}^2$), no-vibrating and massive structure in the underground. For the performance of this concrete, we investigate and select all materials, the optimum mix design and sensibility test in the laboratory. As test results, we choose portland blast-furnace slag cement and lime stone powder(L.S.P) as cementitious materials, W/C 41%(W/B 35.4%), S/a 50.8% and unit volume of coasre aggregate 0.30 as optimum mix design. Also test result of the fresh and hardened concrete are satisfied with specifications of slurry wall.