• Nuclear Engineering and Technology
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• v.56 no.9
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• pp.3942-3949
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• 2024

This study focuses on investigating the chemical degradation characteristics of cementitious barriers used in low-and intermediate-level radioactive waste repository by reactive transport modeling. The impact of the blending with supplementary cementitious materials (SCMs) in the barriers on the chemical degradation was evaluated to find the optimum barrier design. A number of different barrier designs were examined by replacing ordinary Portland cement (OPC) by SCMs (i.e., fly ash, silica fume, and blast-furnace slag). The simulation results showed that silica fume blended barrier has better durability against chemical degradation by rainwater compared to fly ash or blast-furnace slag blended barriers. In addition, the chemical durability of silica fume-based barrier increased with increasing replacement level up to about 20 %. It seems that the amount of formed calcium silicate hydrate (CSH) in the initial cement-based barrier highly affects the overall chemical durability. The newly developed reactive transport model demonstrated its capability for understanding the barrier performance and investigating the optimal design of the barrier system.

• 한국약용작물학회:학술대회논문집
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• 2010.10a
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• pp.187-188
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• 2010

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.565-566
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• 2009

Supplementary cementing materials (SCM), such as silica fume, slag, and low-calcium fly ash, have been widely used as mineral admixtures in high strength and high performance concrete. Due to the chemical and physical effect of SCM on hydration, compared with Portland cement, hydration process of cement incorporating SCM is much more complex. This paper presents a numerical hydration model which is based on multi-component concept and can simulate hydration of cement incorporating SCM. The proposed model starts with mixture proportion of concrete and considers both chemical and physical effect of SCM on hydration. Using this proposed model, this paper predicts the following properties of hydrating cement-SCM blends as a function of hydration time: reaction ratio of SCM, calcium hydroxide content, heat evolution, porosity, chemically bound water and the development of the compressive strength of concrete. The prediction results agree well with experiment results.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.577-580
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• 2006

This paper presents the experimental results of frost durability characteristics including freezing-thawing and de-icing salt scaling of the concrete used for gutter of the road. Mixtures were proportioned with the three level of water-binder ratio (W/B), 0.58, 0.53, and 0.48, and two binder compositions corresponding to Type I cement without any supplementary cementitious materials (OPC) and Type I cement with 30% blast-furnace slag replacement (Slag30). Also, two different solutions of calcium chloride and water that contains 0 and 8g of anhydrous calcium chloride in each 100 mL of solution, respectively, were used to evaluate their effect on the frost durability resistance. Test results showed that the Slag30 mixture exhibited higher durability factor and lower mass loss values than those made with OPC. Among the mixture tested in this work, the mixtures (OPC and Slag30) made with a relatively higher W/B of 0.58 exhibited large amount of the de-icing salt scaling regardless of calcium chloride concentration. Finally, the use of slag can be used effectively in terms of economy and frost durability of the concrete designated for gutter.

• International Journal of Concrete Structures and Materials
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• v.18 no.2E
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• pp.97-102
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• 2006

In this study, the effect of supplementary materials(GGBS, PFA, SF) on sulfuric acid corrosion resistance was assessed by measuring the compressive strength, corroded depth and weight change at 7, 28, 56, 91, 180 and 250 days of immersion in sulfuric acid solution with the pH of 0.5, 1.0, 2.0 and 3.0. Then, it was found that an increase in the duration of immersion and a decrease in the pH, as expected, resulted in a more severe corrosion irrespective of binders: increased corroded depth and weight change, and lowered the compressive strength. 60% GGBS mortar specimen was the most resistant to acid corrosion in terms of the corroded depth, weight change and compressive strength, due to the latent hydraulic characteristics and lower portion of calcium hydroxide. The order of resistance to acid was 60% GGBS>20% PFA>10% SF>OPC. In a microscopic examination, it was found that acid corrosion of cement matrix produced gypsum, as a result of decomposition of hydration products, which may loose the structure of cement matrix, thereby leading to a remarkable decrease of concrete properties.

• Journal of the Korean Society of Food Culture
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• v.17 no.5
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• pp.646-652
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• 2002

In this study, we selected supplementary vegetable resources to develpe nutritious supplementary model of korean formula for infants and children, purchased and analyzed it to use with a model. We also referred to an old book about Korean vegetable resources and searched a form of vegetable resources. There are a lot of vegetable resources of various kinds which lied scattered in mountains and fields of our country. As for these, a beyond compare menstruation activity component is becoming clear with a lot of things. It is thought that depth search and study of these vegetable resources and practical application to a infant and child supplemen is desirable. Therefore, we choosed vegetable resources ; a Capsella brusapastoris, a Codonopsis lanceolata, Dandelion, a wild plant, a Tractylis ovata(dried), a Tractylis ovata(native), a Pine plant, a burdock, a JanDae, a Plantain, a HollpDae, which gathered in our country, and we analyzied priximate aomposition of sample (moisture, ash, total carbohydrate, crude fat, crude protein, dietary fiber) and micronutrient contents of sample (calcium, Iron, flavonoids, vitamin A, vitamin C, vitamin E).

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.127-128
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• 2022

In order to realize carbon neutrality in the international society, research on supplementary cementitious materials(SCMs) has been actively conducted as a way to reduce carbon dioxide emissions in the cement industry. However, the use of SCMs causes problems of initial hydration delay and strength reduction due to the reduction of tricalcium silicate(C3S) in the cement clinker. Therefore, in this study, the initial hydration and basic characteristics of cement mortar were confirmed by adding a C-S-H based hardening acceleration to blended cement mixed with Portland cement, blast furnace slag, fly ash, and limestone power. As a result of the heat of hydration and compressive strength test, it was confirmed that when hardening acceleration was added, the initial reactivity was high, so the heat of hydration was promoted, and the initial strength was increased. It is considered to be due to C-S-H seeding effect. Therefore, it is judged that the use of C-S-H based hardening acceleration can supplement the problem of initial hydration delay of blended cement in Korea.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.1
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• pp.170-176
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• 2002

The objective of this study was to investigate the current status of calcium fortification in processed foods for obtaining basic data on nutrition fortification policy and nutrition labeling, Surveyed samples were the products fortified wish calcium among processed products sold in department store and large mart in Seoul from Aug. 1998 to Aug. 1999. But supplementary health food or special nutritious food and weaning food and infant formula were excluded from them. We examined the kinds and numbers of added nutrients except calcium and the amounts of calcium per 100 g product and nutrient labeling of calcium-fortified foods. Surveyed products were 81 foods and they were grouped in grain products, milk and milk products, processed meat and fishes, ramyuns, retort pouch foods, fruit juice and drinks. and others. Calcium fortification was found in wide food groups, especially in snack foods and carbonated beverages. In relation to surveyed products, most of them were fortified with only calcium. The number of added nutrients in the product were relatively various in comparison with each food groups. In addition to calcium, the most frequently added nutrient was DHA, and were followed vitamin, mineral, oligosacchride, fiber, etc. This result showed that the kind(s) and the number(s) of nutrient added to product did not consider nutrition balance of calcium-fortified foods. Units of calcium content were decided by companies, therefore consumers confused labelled content with mouth dose of calcium and the comparison of the amounts added calcium among products was difficult. The amounts of calcium in products were from 16.4 to 1226 mg Per 100 and from 2.5 to 27.6% RDA (recommended daily allowance) per serving size. The amounts of calcium in many products were less than 10% RDA per serving size, whole appraisal about fortified content was needed. And for nutrient labeling on calcium, they used various term whether it is approved by law or not.

• Journal of Yeungnam Medical Science
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• v.14 no.1
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• pp.220-226
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• 1997

Idiopathic hypoparathyroidism is frequently associated with intracranial calcification and neuropsychiatric abnormalities. The most commonly recognized central nervous system manifestations of chronic hypoparathyroidism are seizure, alteration of mental function and extrapyramidal signs. We present a case of hypoparathyroidism, demonstrating extensive intracranial calcification, not only basal ganglia, but also outside the extrapyramidal system. An 58-year-old woman presented with 30 year history of seizure and memory disturbance. The physical examination and several laboratory studies disclosed normal. However hypocalcemia, hyperphosphatemia with hypocalciuria and decreased parathormone level were demonstrated. Clinical symptoms and signs showed improvement after supplementary calcium and Vit $D_3$ therapy.

• Computers and Concrete
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• v.17 no.5
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• pp.655-672
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• 2016

A predictive model for chloride binding isotherms of blended cements with various supplementary cementitious materials (SCMs) was established in this work. Totally 560 data points regarding the chloride binding isotherms of 106 various cements were collected from literature. The total amount of bound chloride for each mixture was expressed a combinational function of the predicted phase assemblage and binding isotherms of various hydrated phases. New quantitative expressions regarding the chloride binding isotherms of calcium-silicate-hydrate (C-S-H), AFm, and hydrotalcite phases were provided. New insights about the roles of SCMs on binding capabilities of ordinary portland cements (OPC) were discussed. The proposed model was verified using separate data from different sources and was shown to be reasonably accurate.