• Journal of the Korea Institute of Building Construction
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• v.22 no.6
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• pp.663-672
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• 2022

The purpose of this study is to evaluate the magnesium sulfate resistance of a geopolymer mixed with rice husk powder. General concrete, silica fume mixed concrete, and binary blended geopolymer were selected as comparison targets to confirm the magnesium sulfate resistance, and sulfate deterioration was calculated using the compressive strengths with ages. In addition, the weight change rate and the relative dynamic coefficient of the geopolymer were comparatively analyzed, and the degree of etteringite formation was confirmed using X-ray diffraction analysis. the experiment, the geopolymer mixed with 10% rice husk powder showed 10.8% higher compressive strength than concrete with silica fume when submerged for 56 days. Also, the geopolymer mixed with rice husk powder showed a small weight change rate of 0.9 to 1.45%. composition after immersion in magnesium sulfate through X-ray diffraction analysis, it was observed that a small amount of ettringite was dispersed in the geopolymer containing rice husk powder. Thus, there is a high correlation with the corrosion resistance of magnesium sulfate

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.1
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• pp.15-22
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• 2010

Chloride-induced corrosion of steel bars in concrete exposed to marine environments has become one of the major causes of deterioration in many important facilities made of reinforced concrete. A study on chloride penetration in concrete has developed through long period exposure test along seawater, assesment of chloride ion diffusion by electrochemical techniques and so on. However, reasonable and exclusive chloride penetration model considering concrete material properties with mixture, degree of hydration, binding capacity has not been established. Therefore, in this paper, chloride penetration analysis of non-steady state is accomplished with material properties of concrete. Comparing with the results of analysis and chloride ponding test, we could accept the effect of binding capacity on chloride penetration in concrete and these results could be applied to a service life prediction of R.C. structures submerged in seawater. Therefore, there are 20~40% differences of service life to SHRP prediction.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.63-69
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• 2010

This study investigates the chemical resistance of the recycled aggregate concrete containing calcined ground slag, fly ash, and diatom powder. The recycled aggregate which had the density of $2.48g/cm^3$, the absorption of 4.25%, and standard gradation was used and the concrete specimens were submerged in solutions of $Na_2SO_4$ and $CaCl_2$ at 10% concentration for 6 months. As the submersion result, pore volume of over $0.02{\mu}m$ diameter was formed less in the concrete specimens containing calcined ground slag, fly ash, and diatom powder than in the concrete without the pozzolanic materials and the result shows the effectiveness of the pozzolanic materials for the increase of chemical resistance of the recycled aggregate concrete.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1188-1194
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• 2014

The purpose of this study is to estimate Chloride Attack Resistibility and mechanical properties of quaternary concrete adding fly ash, blast-furnace slag, and silica fume. Compressive strength, modulus of elasticity, chloride migration coefficient, charge passed from Rapid chloride penetration test(RCPT), and immersion testing in 3% NaCl are tested. Chloride migration coefficient and charge passed of quaternary concrete measured $0.032{\times}10^{-12}m^2/sec$ and 650 coulomb at 17 weeks, which are in a permitted limit. Also in immersion test, depth of chloride penetration and maximum chloride ion of quaternary concrete measured 3.7 mm and $10.211kg/m^3$ respectively. From the results, quaternary concrete adding fly ash, blast-furnace slag, and silica fume denotes improvement of mechanical properties and chloride attack resistibility.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.10a
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• pp.161.2-162
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• 2003

감 장아찌 가공적성이 높은 떫은감품종을 선발키위해 연구한 결과 시험처리전 떫은감 과실특성으로 과중은 갑주백목, 상주둥시 품종이 무거웠고 당도는 고종시, 청도반시 품종이 높았다. 장아찌 경도는 침지후 14일까지 저하되었다가 그 이후 증가되었으며 품종별 증가되는 비율은 사곡시가 다소높았다. 장아찌염도는 침지후 14일까지는 많이 증가되었으나 그이후 염도변화는 적었으며 품종별로는 고종시가 가장 낮았다. 염장중 탈삽정도는 침지초기(14일후)에 대부분 품종들은 탈삽지수가 3이하로 떫은맛을 느낄수가 없었으며 떫은감 품종중 도근조생과 사곡시품종이 다른 품종에 비해 탈삽정도가 양호하였다. 떫은감 품종별 물성검사 결과 경도가 높은 품종은 도근조생과 고종시였고 낮은 품종은 월하시와 청도반시였다. Adhesiveness에서는 고종시와 청도반시에서 높았고 사곡시와 상주둥시에서 낮았다. Springiness에서는 대부분의 품종에서 비슷하였으나 청도반시와 사곡시 품종에서 다소 높았다. 고종시와 상주둥시 품종에서 Gumminess와 Chewiness가 높았다. 떫은감 품종별 관능검사결과 상주둥시, 월하시, 고종시, 도근조생, 사곡시등의 품종이 식미지수가 2.4이상으로 우수하였으나 상주둥시, 월하시, 고종시 등의 품종은 씨를 함유하기 때문에 장아찌 가공에 부적합하였고 도근조생, 사곡시등의 품종은 식미지수가 3.1, 3.0으로 우수할 뿐만 아니라 씨가 없어 장아찌가공에 적합한 품종이었다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.1-8
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• 2019

The primary purposes of this study are to understand a fundamental effects of electro-deposition on reinforcing steel in saturated Ca(OH)2 electrolyte, and evaluate the corrosion rates of rebars under cyclic 3wt.%NaCl immersion and dry corrosion environment. The three cement mortar specimens with cover thickness 5, 10 and 30mm, were prepared in the experiment. To monitor the corrosion rates of rebars in mortar, the three cement mortar specimens were exposed to 110 wet-drying cycles(8-hour-immersion in 3wt.%NaCl and 16-hour-drying in a room temperature) in the laboratory. During the wet-dry cycles, the polarization resistance, Rp, and solution resistance, Rs, were continuously measured. The instantaneous corrosion rates of rebars on the effect of electro-depositing with sat. Ca(OH)2 electrolyte were estimated from obtained R-1p and degrees of wetness were estimated from Rs values. From the experimental results, the corrosion rates of rebars were greatly accelerated by wet/dry cycles. During the mortars exposed to drying condition, the large increases in the corrosion rates were showed at all rebar surfaces in three mortar specimen, attributed from the accelerated reduction rates of dissolved oxygen in drying process. However, the corrosion rates on rebar surface electrochemically deposited with sat. Ca(OH)2 electrolyte showed the clear decreases, caused by calcium deposits in the porous rust layer.

• Journal of Ocean Engineering and Technology
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• v.17 no.3 s.52
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• pp.39-45
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• 2003

Shot peening is an effective method of improving the fatigue strength of components and structures. The compressive residual stress produced by surface plastic deformation with shot peening is usually regarded as the major factor in increasing fatigue strength. In this study, the influence of shot peening on corrosion was investigated. Spring steel immersed in $3.5\%$ NaCl prior was used to evaluate the effect of shot peening on fatigue properties. The immersion test was performed on the five kinds of specimens with shot peened and unpeened. The distributions of residual stresses of shot peened spring steels were measured in an X-ray diffraction apparatus, using the two-point method. Corrosion potential, polarization curve, residual stress, etc. were investigated, based on the experimental results. From test results, the effect of shot peening on the corrosion was evaluated.

• Journal of Food Hygiene and Safety
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• v.35 no.2
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• pp.183-188
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• 2020

The manufacturing process for konjac jelly is largely divided into the three processes of powder manufacturing, a coagulation and finishing. It was found that the number of aerobic bacteria in konjac jelly decreases as the concentration of coagulation agent and soaking liquid increases. The temperature of the water has no significant effect. When the concentration of coagulation agent was maintained at 1.0%, the tensile strength was also maintained without significant change for up to 10 months. When the concentration was kept below 0.8%, however, the tensile strength showed a tendency to sharply decrease. After fixing the coagulant concentration to 1.0%, the effect by the soaking liquid was confirmed. At all concentrations of soaking, it was found that both tensile strength and bacterial numbers are unchanged until 10 months of storage.

• Korean Journal of Food Science and Technology
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• v.23 no.2
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• pp.229-234
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• 1991

Attempts were made to improve the textural quality of French-fried potato produced with S potato varieties popular in Korea. The most suitable variety to produce French-fried potato, among 5 varieties tested, was Superior. Texture of French-fried potato was improved by air drying blanched potato strips at room temperature for over 1 hour, immersing potato strips in 6% starch solution at $60^{\circ}C$ for 2 minutes, and immersing in 1.5% hydroxypropyl methyl cellulose(HPMC) solution at $60^{\circ}C$ for 2 minutes. Textural quality of French-fried potato was significantly improved, when blanched potato strips were subjected to air drying at room temperature for 1 hour, followed by immersing them in 1.5% HPMC solution at $60^{\circ}C$ for 2 minutes prior to frying.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.1-9
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• 2004

This paper represents the permeability of chloride ions and the corrosion performance in the concrete blended with granulate blast furnace slag exposed to chloride environment. An ordinary cement (type I ) and sulfate resisting cement(type V) were used for the experiment. The two cements were combined with $0\%$, $25 \%$, $40\%$, and $55\%$ of the granulated blast furnace slag. The accelerated permeability tests of chloride ions were performed in accordance with ASTM C1202, and the accelerated corrosion tests of steel were carried out by using the method of immersion/drying cycles. After water curing 28 days, 56 days and 91 days, these tests were conducted until 30 cycles. In every cycle, test specimens were wetted in $3\%$ NaCl solution for three days and dried again in $60^{\circ}C$ air for four days. As an experimental results, the diffusion coefficient of chloride ions of the ordinary cement Concrete Combined granulated blast furnace slag was much lower than that of non granulated blast furnace slag concrete. Moreover, the diffusion coefficient of chloride ions of sulfate resisting cement concrete was higher than that of ordinary cement concrete. On the basis of the results of accelerated corrosion tests, corrosion resistance of the concrete mixed with granulated blast furnace slag shows good to corrosion resistance, however, the concrete with sulfate resisting cement shows bad to corrosion resistance.