• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.2
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• pp.152-160
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• 2021

Converter steel slag(BOF slag) is a vast amount of solid waste generated in the steelmaking process which has very low utilization rate in Korea. Due to the presence of free CaO which can derive bad volume stability in BOF slag, it usually land filled. For recycling BOF and identify its applicability as fine aggregate, this study investigates the fundamental characteristics of mortar with cement replaced ferronickel slag(FNS), which has the potential to be used as a binder. The results suggest that the mineral phases of BOF slag mainly include larnite(CaSiO₄), mayenite(Ca₁₂Al₁₄O₃₃) and wuestite(FeO) while olivine crystallines are shown in FNS. The results of flow and setting time reveals that the flowability and process of hardening increased when the amount of FNS and BOF slag incorporated was increased. The length change shows that the amount of change in the length of the mortar was almost constant regardless of mix proportion while compressive strength was reduced. Micro structure test results revealed that FNS or/and BOF slag mix took a long time to react in the cement matrix to form a complete hydration products. To achieve the efficient utilization of B OF slag as construction materials, proper replacement rate is necessary.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.363-372
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• 2022

Precast concrete is an effective method to increase the construction quality and construction speed by optimizing and making the manufacturing conditions similar. In order to more effectively produce a fireproof material-integrated precast duct slab, the purpose of this study was to determine whether the fire resistance performance of the fireproof layer is maintained when a method of increasing the curing rate using a hardening accelerator is used. As a result of performing a fire resistance performance test on specimens classified according to whether or not the hardening accelerator was included, increase of temperature inside the specimen was high in the specimens using the hardening accelerator, and the section loss of the fireproof layer occurred locally on the surface exposed to fire heating. In conclusion, it is judged that the fireproof layer in the case where the strength at 3th day of age is gained within 1 day curing age using a hardening accelerator does not guarantee sufficient fire resistance performance in the conditions used in this study.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.553-557
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• 2022

The present study evaluate the chloride extracion under electrochemical chloride extraction method. Chloride was penetrated into the concrete from external reservoir using a 4M NaCl solution, and an electrochemical chloride extraction method was applied after the curing period of 1 year. The current density was constantly kept 1000 mA/m² for coulostatic application with the variation in potential difference. The duration of the ECE treatment was 2, 4, 8 weeks, respectively. The residual chloride concentration at all depths decreased, and the chloride concentration decreased as the application period increased. After the application period of 8 weeks, 62.9 to 77.6 % of chloride extracted in the total chloride profile, and 77.7 to 99.5 % of chloride extracted in the free chloride profile. In particular, the concentration of free chloride at a depth of 7 mm or more from the concrete surface was 0.01 % or less by cement. In addition, it was confirmed that the bound chloride could be extracted by the electrochemical chloride extraction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.353-359
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• 2010

Cementitious matrix based composites are vulnerable to the drying shrinkage crack during the curing process. In this study, the drying shrinkage induced fracture behavior of the fiber reinforced concrete is simulated and the effects of the fiber reinforcement conditions on the fracture characteristics are analysed. The numerical model is composed of conduit elements and rigid-body-spring elements on the identical irregular lattice topology, where the drying shrinkage is presented by the coupling of nonmechanical-mechanical behaviors handled by those respective element types. Semi-discrete fiber elements are applied within the rigid-body-spring network to model the fiber reinforcement. The shrinkage parameters are calibrated through the KS F 2424 free drying shrinkage test simulation and comparison of the time-shrinkage strain curves. Next, the KS F 2595 restrained drying shrinkage test is simulated for various fiber volume fractions and the numerical model is verified by comparison of the crack initiating time with the previous experimental results. In addition, the drying shrinkage cracking phenomenon is analysed with change in the length and the surface shape of the fibers, the measurement of the maximum crack width in the numerical experiment indicates the judgement of the crack controlling effect.

• Journal of the Korean GEO-environmental Society
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• v.16 no.12
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• pp.45-52
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• 2015

With the rising interest in the environment, more attention on ecological restoration for damaged slope surface to restore its original state has been drawn. Generally, the most useful method is vegetation based spray work. This method uses green soil including sewage sludge, sawdust, paper sludge, and weathered granite soil. However, because there are neither accurate information nor test values about green soil, green soil is often lost by environmental factors such as rainfalls and strong winds. To solve the problem of green soil, it is necessary to prepare design standards about green soil, and conduct studies to deal with green soil loss in consideration of various variables including basic material property, soil quality of slope surface, and weather. This study was conducted in the mixture of green soil and eco-friendly soil stabilizer. With green soil, basic material property test and compaction test were conducted for the analysis on the basic characteristics of green soil. In the mixture with soil stabilizer at a certain ratio, we conducted shear strength test depending on the ratio in order to analyze the maximum shear strength, cohesion and the change in internal friction angles. Furthermore, in the mixture ratio of green soil and soil stabilizer, which is the same as the ratio in the shear strength test, an inclination of slope surface was made in laboratory for the analysis on erosion and germination rate. Finally, this study evaluated the most effective and economic mixing ratio of soil stabilizer to cope with neighboring environmental factors. According to the test, the shear strength of green soil increased up to 51% rely onto the mixing ratio of and a curing period, and its cohesion and internal friction angle also gradually increases. It is judged that the mixture of soil stabilizer was effective in improving shear strength and thereby increased the stability of green soil.

• Journal of Korean Medical Ki-Gong Academy
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• v.7 no.2
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• pp.40-94
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• 2004

Recently, meditation, Zen meditation and Qigong became popular in western. For that reason, Value of Korea traditional methods for health promotion have been evaluated but theoretical evidence about that is insufficient. ${\ll}$The Yellow Emperor's Inner Classic${\gg}$ (黃帝內經). So, I reviewed history of Korea Qigong according to period, in order to produce theoretical evidence of Korea medical Qigong and investigated ${\ulcorner}$Han${\lrcorner}$ thought (${\ulcorner}$한${\lrcorner}$ 思想) as theoretical evidence of Korea Qigong. I have obtained following results by comparing meaning of god, a view of human body and practice method of the ${\ll}$Samilshingo${\gg}$ (三一神誥) with ${\ll}$The Yellow Emperor's Inner Classic${\gg}$ (黃帝內經). Sinsundo(神仙道) of native to race became active during the period of the Three Kingdoms but more disappeared due to under the influence of Taoism. So only has been remained in existence since the period of the unity silla. There could accept positively the foreign ideas belonging to Confucianism, Buddhism and Taoism have been brought since the period of the Three Kingdoms because ${\ll}$Samilshingo${\gg}$ (三一神誥), one of three the scriptures as the origin of ${\ulcorner}$Han${\lrcorner}$ thought(${\ulcorner}$한${\lrcorner}$ 思想) included the original form of three religion belonging to Confucianism, Buddhism, Taoism. Three common results as theoretical evidence of Qigong were found out by comparing ${\ll}$Samilshingo${\gg}$ (三一神誥) with ${\ll}$The Yellow Emperor's Inner Classic${\gg}$ (黃帝內經). First, in meaning of god, there is not only different from the gods of heaven and the gods of human but also keep understanding with each other and there was common feature of logical structure that function of god was divided into three. Second, In a view of human body, there were in common with ${\ll}$Samilshingo${\gg}$ (三一神誥) as theory of only as energy(氣一元論), theory of bisection as truth false(眞妄二分論), theory of trisection as spirit(性) destiny(命) nature(精) and mind(心) energy(氣) body(身)(性 命 精, 心 氣 身의 三分論) and ${\ll}$The Yellow Emperor's Inner Classic${\gg}$ (黃帝內經) as theory of only as energy(氣一元論), theory of bisection as shape and god(形神二分論), theory of trisection as nature(精) energy(氣) god(神) or shape(形) energy(氣) god(神)(精 氣 神, 形 氣 神의 三分論) according to formal part. Also, spirit(性) destiny(命) nature(精) as truths of three(三眞) were understand as nature(精) energy(氣) god(神) as treasure of three(三寶) by part of reason and mind(心) energy(氣) body(身) as false of three(三妄) were understand as nature(精) energy(氣) god(神) as treasure of three(三寶) by part of function. Third, In practice method, pause of thinking(止感) modulation of breath(調息). prohibition of sensibility(禁觸) mentioned in ${\ll}$Samilshingo${\gg}$ (三一神誥) as practice method each were understand regulation of an etiological cause as an internal cause, an external cause and not internal and external cause in oriental medicine. Namely, pause of thinking(止感) was understand as regulation method of emotion, mind and nature. modulation of breath(調息) was not only as modulation of energy from the inner parts of the body but also that from the internal and external parts of the body, prohibition of sensibility(禁觸) was understand as regulation method of ear, eye, mouth, and nose and posture, life style. These results suggest that ${\ll}$Samilshingo${\gg}$ (三一神誥) is worth meaning of Korea medical Qigong because meaning of god, a view of human body, practice method of mentioned in ${\ll}$Samilshingo${\gg}$ (三一神誥) is common with that of ${\ll}$The Yellow Emperor's Inner Classic${\gg}$ (黃帝內經) as theoretical evidence of Qigong.