• Magazine of the Korea Concrete Institute
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• v.9 no.2
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• pp.121-132
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• 1997

The thermal behavior of' concrete can be ch;lracterized from a knowledge of concrete ternperatu1.e at early ages, environmental conditions, and cement hydration in the mixture. 'l'o account for thost. interactions, a computer model was developed for prwlicting the temperature pr.ol'ile in hnrdcning c o n c r c t ~ st.r~icture in terms of material and tmvironmcntal factors. The cerncnt hydration cha~.acteristics such as the activating energy, total heat 1ihei.atr.d. anti th\ulcorner degree of' hydration. can represent the internal heat gc,neration. In this study. th(> activating c1ncrgy and the tlcgree of' hydration curve were determined well fmm the rnortn~. compressive strength tests while total amount of heat liberated was determined by tht> isothermal calorimctcr method. The main purpose of' this study is to correlate measured tt>mperaturr distributions in a concrete st1,ucture during thc hardening process with the ~ c s u l t s computed f'ro~n theoretical considrl.ations. Using twodimensional heat transfer model, first. the importance of several parameters will be identified by a parametric analysis. Then, the tcmpcmture distribution of thc cylindrical concrete specimen in the laboratory was mensuwti and compared with that yielded by thc theoretical considel.ations.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.31-32
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• 2011

Granulated slag from metal industries and fly ash from the combustion of coal are industrial by-products that have been widely used as mineral admixtures in normal and high strength concrete. Due to the reaction between calcium hydroxide and fly ash or slag, the hydration of concrete containing fly ash or slag is much more complex compared with that of Portland cement. In this paper, the production of calcium hydroxide in cement hydration and its consumption in the reaction of mineral admixtures is considered in order to develop a numerical model that simulates the hydration of concrete containing fly ash or slag. The heat evolution rates of fly ash- or slag-blended concrete is determined by the contribution of both cement hydration and the reaction of the mineral admixtures. Furthermore, the temperature distribution and temperature history in hardening blended concrete are evaluated based on the degree of hydration of the cement and the mineral admixtures. The proposed model is verified through experimental data on concrete with different water-to-cement ratios and mineral admixture substitution ratios.

• Korean Journal of Exercise Nutrition
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• v.25 no.4
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• pp.10-16
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• 2021

[Purpose] The purpose of this study was to (i) assess hydration levels in elite male football players during a national team training camp before and during qualifying matches, (ii) evaluate the effect of coaching strategies for hydration based on feedback from hydration monitoring, and (iii) assess possible relationships between hydration status and training load or wellness markers. [Methods] Thirty-one male players (age 27±4 yrs; height 185±6 cm; weight 82.9±6.7 kg; body fat 10.4±2.3%) representing a national team from the Union of European Football Associations (UEFA) participated. The players were studied during three different national team training camps related to the UEFA Nations League tournament. Urine specific gravity (U_SG) was measured to assess hydration status. During all camps, the players were actively coached on improving strategies for hydration and given individual feedback on their test results. The training load was measured using GPS technology, and wellness questionnaires were completed. [Results] U_SG decreased progressively and significantly (p<0.005) during camp 1 and hydration status improved over the three camps, with fewer dehydrated and more well-hydrated players identified during the last part of camp 3. Significantly (p<0.05) higher U_SG values were observed 2 days prior to a match (MD-2) than on match day (MD); consequently, 52% of the players were dehydrated on MD-2 and only 6% on MD. No correlations were observed between hydration status and training load or wellness markers. [Conclusion] Dehydration is a challenge in elite male football, but continuous monitoring of hydration status and coaching on hydration strategies can lead to major improvements and reduce the degree of dehydration.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2011.10a
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• pp.39-41
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• 2011

The recycling rate of recovered paper in Korea is the highest in the world, 92%, but remanufacturing yield is low due to the extremely poor quality of the paper. The poor quality, in turn, influences to the reject amount in deinking process. To increase the yield of old newspaper recycling process, hydrophobic degree of inorganic pigments of deinking stock must be reduced. To determine the hydrophobicity, Pitch Potential Deposit Tester (PDT) was newly designed and applied with respect to the SB latex property of various quality used in Korea; its hydrophobic degree according to Tg, gel content, charge and particle size of latex and optimum designing condition of SB latex. And below are the conclusions: 1. The reason of excessive reject from old newspaper deinking process for total amount of printed ink is loss of inorganic pigments. When lipase, a biochemical catalyst, was applied with the purpose of preventing inorganic pigments loss about more than 70% of total reject weight and promoting hydration of pulp for deinking, deinking process yield of pre flotation secondary stage increased remarkably without any changes of deinking efficiency. 2. Lipase improved deinking stock by cutting ester linkage on surface of hydrophobic materials to promote its hydration. From this, it reached the conclusion that hydration degree of stock exercises significant effect on flotation deinking process yield. 3. Inorganic alkali promotes hydration of deinking stock. But there have been needs for more fundamental measures other than inorganic alkali of promoting hydration for yield improvement. For this, this study intended to find out reasons of chemical properties change on surface of hydrophobic material by change of pH. 4. Pitch Deposit Test (PDT) was performed for understanding principle of why surface of coating flake from OMG is hydrophobic and why it becomes hydrophilic when pH of stock is alkaline. As a result of this test, it is determined that swelling property by change of pH of latex film, which were used as coating adhesive is the reason for hydrophobic change. 5. Hydrophilicity of coating flake increased with hydrophilic pigments. And as more of SB Latex adhesive was used and higher of calcium hardness of stock became, its hydrophilicity decreased. SB Latex adhesive film is reformed by mechanical friction. For having hydrophilicity under neutral pH, strong bruising action such as kneading is required. 6. Because swelling of adhesive film decreases as Tg of SB latex gets lower and mean diameter gets smaller, it shows hydrophobicity under neutral pH. This lowers hydrophilicity of coating flake, which leads to easy elimination with flotation reject on DIP process. Therefore, for improving future flotation yield, it is necessary to develop to use eco-friendly clean SB latex by raising Tg and increasing mean diameter for recycling, and as a result, to reduce excessive loss of coating flake as a reject from deinking process.

• Resources Recycling
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• v.27 no.1
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• pp.92-105
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• 2018

The present study was carried out to find a suitable drying method for measuring non-evaporable water contents of various hydraulic inorganic materials. In Part 1 of the paper, the case Ordinary Portland cement is discussed. Various drying methods including vacuum and oven drying, and an ignition, were used for the OPC paste and mortar having different w/c. The sole vacuum drying under room temperature led a fluctuation on measurement of hydration degree, while the sole oven drying also yielded unwanted hydration promotion at the early age. A combination of the vacuum and oven drying was considered as a suitable drying method for the OPC case.

• Korean journal of food and cookery science
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• v.7 no.2
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• pp.25-40
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• 1991

Five-brown-rice-variety, Akibare, Odaebyeo, Taebaegbyeo, Nonglim Na 1 and Hankangchalbyeo, was prepared and examinated the hydration kinetics and the cooking qualities. Before the hydration the L/W ratio of raw Taebaegbyeo was the biggest value among the five brown rices. The water uptake was directly proportional to the square root of soaking time. During the hydration water uptake of high yielding brown rices was bigger than those of traditional brown rices among the nonglutenious varieties but waxy brown rices were not. Generally volume increase constant was directly proportional to the water uptake constant, which were different a little with brown rices was hydrated which was inversed proportional to the water uptake degree. According to the instrumental result using the rheometer of cooked brown rice with increased soaking times that was decreased the hardness and was increased the adhesiveness. The sensory evaluation test indicated that the hardness and the stickiness value of cooked brown rices were proper after 15-hour-soaking time and it was identical result to the instrumental result using the rheometer.

• Computers and Concrete
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• v.17 no.2
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• pp.173-188
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• 2016

Generally, thermal stress induced by hydration heat causes cracking in mass concrete structures, requiring a thorough control during the construction. The prediction of the thermal stress is currently undertaken by means of numerical analysis despite its lack of reliability due to the properties of concrete varying over time. In this paper, a method for the prediction of thermal stress in concrete structures by adjusting thermal stress measured by a thermal stress device according to the degree of restraint is proposed to improve the prediction accuracy. The ratio of stress in concrete structures to stress under complete restraint is used as the degree of restraint. To consider the history of the degree of restraint, incremental stress is predicted by comparing the degree of restraint and the incremental stress obtained by the thermal stress device. Furthermore, the thermal stresses of wall and foundation predicted by the proposed method are compared to those obtained by numerical analysis. The thermal stresses obtained by the proposed method are similar to those obtained by the analysis for structures with internally as well as externally strong restraint. It is therefore concluded that the prediction of thermal stress for concrete structures with various boundary conditions using the proposed method is suggested to be accurate.

• Journal of the Korea Concrete Institute
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• v.27 no.2
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• pp.115-125
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• 2015

This study investigated the fluidity, heat of hydration, setting time, strength development, and characteristics of hydration and pozzolanic reactions of high-strength high-volume ground granulated blast-furnace slag(GGBFS) blended cement pasts with the water-to-binder ratio of 20% by experiments, and analyzed the effects of the replacement ratio and fineness of GGBFS on the hydration and pozzolanic reaction. The results show that, in the high-strength mixtures with low water-to-binder ratio, the initial hydration is accelerated due to the "dilution effect" which means that the free water to react with cement increases by the replacement of cement by GGBFS, and thus, strengths at from 3 to 28 days were higher than those of plain mixtures with ordinary Portland cement only. Whereas it was found that the long term strength development is limited because the hydration reaction rates rapidly decreases with ages and the degree of pozzolanic reaction is lowered due to insufficient supply of calcium hydroxide according to large replacement of cement by GGBFS. Also, the GGBFS with higher fineness absorbs more free water, and thus it decreases the fluidity, the degree of hydration, and strength. These results are different with those of normal strength concrete, and therefore, should be verified for concrete mixtures. Also, to develop the high-strength concrete with high-volume of GGBFS, the future research to enhance the long-term strength development is needed.

• Journal of the Korean Ceramic Society
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• v.45 no.11
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• pp.744-749
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• 2008

The properties of the polymer-modified mortars are influenced by the polymer film, cement hydrates and the combined structure between the organic and inorganic phases. Also, this quality of polymer modified cement strongly depend on weather condition and polymer cement ratio. To overcome this problem, polymer-modified cement were prepared by varying polymer/cement mass ratio (P/C) with $0{\sim}20%$ and constant water/cement mass ratio of 0.5. The effect of polymer on the hydration of this polymer cement is studied on different polymer cement ratio. The results showed that the polymer cement paste have increased the viscosity in addition the amount of polymer dosage and the polymers is completed resulting in a reduced degree of hydration caused by different ion elution amount. Also we know that the reactants is calcium acetate as a results of chemical reaction between acetate group in EVA which is hydrolysis in water and $Ca^{2+}$ ion during hydration of cement.

• Journal of the Korean Ceramic Society
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• v.54 no.2
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• pp.128-136
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• 2017

Fly ash from a circulating fluidized bed combustion boiler (CFBC fly ash) is very different in mineralogical composition, chemical composition, and morphology from coal ash from traditional pulverized fuel firing because of many differences in their combustion processes. The main minerals of CFBC fly ash are lime and anhydrous gypsum; however, due to the fuel type, the strength development of CFBC fly ash is affected by minor components of active $SiO_2$ and $Al_2O_3$. The initial hydration product of the circulating fluidized bed combustion fly ash (B CFBC ash) using petro coke as a fuel is Portlandite which becomes gypsum after 7 days. Due to the structural features of the portlandite and gypsum, the self-cementitious strength of B CFBC ash was low. While the hydration products of the circulating fluidized bed combustion fly ash (A CFBC ash) using bituminous coal as a fuel were initially portlandite and ettringite, after 7 days the hydration products were gypsum and C-S-H. Due to the structural features of ettringite and C-S-H, A CFBC ash showed a certain degree of self-cementitious strength.