• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.518-529
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• 1996

To develope chemical heat pump using available energy sources such as solar heat and many kinds of waste thermal energy we have studied the enhancement effect of inserted fins in cylindical packed bed reactor. Two dimensionnal(radial and circumferential) partial differential eqaetions, concerning heat and masstransfer in CaO packed bad, are solved numerically to describe the characteristics of the reaction of fins inserted reactor and heat transfer. The results obtained by numerical analysis about two dimensional profiles of temperature and conversion in the reactant in the packed bed and exothermic heat amount released from the reactor are follows; -. The insertion of fins in reactor can redue the reaction completion time by half. -. The rate of thermochemical reaction depends of the temperature and concentration and it is also governed by the boundary conditions and heat transfer rate in the particle packed bed.

• Magazine of the Korea Concrete Institute
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• v.7 no.6
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• pp.167-175
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• 1995

A temperature-analysis program, named ${\ulcorner}TAMCON{\lrcorner}$, was developed to predict the temperature rise due to the heat of hydration in hardening concrete. Finite element method was employed to facilitate the temperature analysis for the structures with complex geometry and various boundary conditions. In order to test the validity of the program, the results obtained from TAMCON for the wall-t.ype structure and the mat foundation were compared with the numerical analysis anti experimental data reported previously. As a result, it was found that they were in good agreement. TAMCON may be useful for the temperature control to restrain thermal cracking and the construction management to design the reasonable curing method in mass concrete.

• Magazine of the Korea Concrete Institute
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• v.9 no.6
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• pp.233-241
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• 1997

최근 해안환경하에 있는 콘크리트구조물의 철근부식은 구조물의 내구성 저하 및 유지관리라는 차원에서 커다란 문제점을 가지고 있다. 이와 같은 현상은 해양구조물의 건설이 날로 증가하고 있고, 또 콘크리트 제조시 잔골재의 일부를 염분이 함유된 해사를 사용함으로써 더욱 심각해지고 있다. 본 연구에서는 콘크리트 표면으로부터 침투해 들어오는 침입염분의 거동을 모델화하였으며, 콘크리트 세공속의 수용액상에 있은 염화물이온의 확산을 포함하는 물리 화학적 진행, 시멘트 수화물에 고정되는 염분의 흡착과 탈착 및 고정염과의 화학반응 등의 현상을 유한요소법에 의해 해석을 실시하였다. 본 연구의 결과는 콘크리트 내부의 철근 발청시기의 예측, 해안환경하에 있는 콘크리트 구조물의 침투 염분에 의한 콘크리트 덮개의 결정, 콘크리트 구조물의 염화물이온의 허용치 설정을 비롯하여 내구년수를 예측하는데 유용하게 활용될 수 있을 것으로 기대된다.

• Journal of the Korea Institute of Building Construction
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• v.24 no.2
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• pp.169-180
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• 2024

In this study, to suggest an efficient method of using coal gasification slag(CGS), a byproduct from integrated gasification combined cycle(IGCC), as a combined fine aggregate for concrete mixture, the diverse performances of concrete mixtures with combined fine aggregates of CGS, river sand, and crushed sand were evaluated. Additionally, using CGS, the reduction of the hydration heat and the strength developing performance were analyzed to provide a method for reducing the heat of hydration of mass concrete by using combined fine aggregate with CGS and replacing fly ash with cement. The results of the study can be summarized as follows: as a method of recycling CGS from IGCC as concrete fine aggregate, a combination of CGS with crushed sand offers advantages for the concrete mixture. Additionally, when the CGS combined aggregate is used with low-heat-mix designed concrete with fly ash, it has the synergistic effect of reducing the hydration heat of mass concrete compared to the low-heat-designed concrete mixture currently in wide use.

• Korean Journal of Materials Research
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• v.5 no.3
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• pp.379-386
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• 1995

LiOH-$H_{3}$BO_{3}$ 용액중에서의 Zircaloy-4 핵연료 피복관의 부식가속과 억제현상을 조사하고 이러한 부식특성에 미치는 Li 및 B의 영향을 해석하기 위하여, 여러 조건의 LiOH-$H_{3}$BO_{3}$ 용액을 사용하여 35$0^{\circ}C$, 165bar의 고온, 고압 조건에서 Zircaloy-4 피복관의 노외 부식시험을 수행하였다. 원전 수화학 모의조건에 대응되는 용액 중에서의 부식속도의 천이는 물 분위기에서 보다 빨리 발생되고 천이후 물 분위기와 거의 유사한 부식속도를 나타내는 천이적 후의 부식거동을 보였다. 한편 pH의 변화는 부식특성에 큰 영향을 미치지 않았다. 부식가속과 억제 모의실험으로부터, 산화막내로 침투하는 Li의 양이 용액중 Li 농도에 크게 의존하며, Li 농도가 일정하게 정해진 용액의 경우 B 첨가에 관계없이 산화막내에 일정량의 Li이 농축될수 있다는 가정을 제시하였다. 또한 B 첨가에 의한 부식억제가 B 또는 B-(OH) 화합물의 산화막내 Li 침투 억제에 의한 것이 아니라 일들에 의해 산화막내로 산화성 성분의 이동이 억제되는데 기인할 수 있음을 제시하였다. 부식가속 개시점에 대응되는 산화막 두께측정 결과와 용액내 Li 농도간의 관계로부터, 용액중 Li 농도가 높을수록 부식가속이 얇은 산화막 두께에서 시작됨을 알았다. 특히 노내조건에서의 핵연료 피복관의 부식가속이 산화막내 Li 농축에 의해 일어나는 부식특성으로 해석될 수 있음을 보였다.

• Journal of the Korean Society of Safety
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• v.16 no.4
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• pp.153-159
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• 2001

Recently, the underground reinforced concrete(RC) box structures have been increasingly built in Korea. In such structures, the heat of hydration may cause serious cracking problems. The RC box structures are classified in this category that needs much attention to control the hydration heat during construction, which causes the restraining effects on the boundaries. The purpose of the present study is to develop the rational construction method to control the thermal cracking problem of the box structures. In this study, the causes and mechanism of thermal cracking according to construction stages in the RC box structures are thoroughly analyzed. The major influencing variables are studied through the finite element analysis which affect the thermal cracking of RC box structures. The research results of the present study can be efficiently used for the control of cracking of box structures during construction stages.

• 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.

• Journal of the Korea Institute of Building Construction
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• v.9 no.4
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• pp.139-145
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• 2009

This study presents an estimation of the strength development of concrete considering the equivalent age using fine particle cement (FC), which is manufactured according to the classification process. Contents and W/B were considered as experimental parameters. The strength considering the equivalent age is gradually increased, and the deviation of the strength according to W/C is increased with decrease of W/C in accordance with the replacement of the fine particle cement. For estimating the apparent activation energy (Ea) considering setting time and blame fineness of cement, Ea of the FC based on setting time is calculated with $27.6{\sim}28.9$ KJ/mol, which is somewhat similar to that of OPC, while by applying Ea based on blame fineness, Ea is increased with increase of FC contents, and is calculated with $40{\sim}56$ KJ/mol. Good agreement is obtained by applying Ea based on setting time, while there was remarkable variation between calculated value and measured value when Ea based on blame fineness. Therefore, it is necessary to add influencing factors in existing Ea to enhance the accuracy of the estimation.

• Journal of the Korean Ceramic Society
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• v.34 no.1
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• pp.45-55
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• 1997

Various kinds of amorphous silicates were used as raw materials to synthesize building materials based on calcium silicate hydrates. Relationships between the reactivities of silicates and castabilities of the building materials were investigated. In addition, effects of the reactivities of silicates on the mechanical properties of casted specimens were studied by analyzing microstructures and hydrates produced. As the reactivity of silicate increase, the press castability increases and the crystal size of hydrate and pore size also increase. For the mechanical properties, the flexural strength increases with decreasing crystal size and densifing microstructure. The compressive strength is greatly dependent on the den-sification of microstructure rather than crystal size of hydrate. Based on the results, diatomous ma-terials are desirable due to high reactivity and formation of densified microstructure. Slag and fly ash may be partially used as raw materials with amorphous silicates to manufacture building materials based on calcium silicate hydrates.

• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1181-1191
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• 1996

To develope chemical heat pump, which is operated by heat of high temperature using available energy sources such as solar heat and many kinds of waste thermal energy we have studied theoretically the enhancement effects of inserted fins on the rate of heat transfer and reaction in cylinderical $Ca(OH)_2$ packed bed reactor. The results obtained by numerical analysis about profiles of temperature, completion time of reaction and exothermic heat amount released from the reactor read as the inserted copper fins in reator reduce the completion time of dehydration reaction in packed bed by half, and the rate of thermochemical reaction depends on the temperature and concentration, and it is also governed by the boundary conditions and the rate of heat transfer in the particle packed bed.