• International Journal of Concrete Structures and Materials
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• v.19 no.1E
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• pp.41-48
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• 2007

Addition of latex to concrete is known to increase its durability and permeability. The purpose of this study is to analyze air void systems in latex-modified concretes using a reasonable and objective method of image analysis with such experimental variables as water-cement (w/c) ratios, latex contents (0%, 15%) and cement types (ordinary portland cement (OPC), high-early strength (HES) cement and very-early strength (VES) cement). The results are analyzed by spacing factor, air volume (content) after hardening, air void distribution and structure. Additionally, air void systems and permeability of latex-modified concrete (LMC) are compared by a correlation analysis. The results are as follows. The LMC of the same w/c ratio showed better air entraining (AE) effect than OPC with AE water reducer. The VES-LMC showed that the quantity of entrained air below $100{\mu}m$ increased more than four times. For the case of HES-LMC, microscopic entrained air between the range of 50 to $500{\mu}m$ increased greater than 7 times even in the absence of anti-foamer. Although spacing factor was measured rather low, the permeability of latex-modified concrete was good. It is construed that air void system does not have a considerable effect on the property of latex-modified concrete, but latex film (membrane) has a definite influence on the durability of LMC.

• Journal of mucopolysaccharidosis and rare diseases
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• v.2 no.1
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• pp.5-7
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• 2016

Mucolipidoses II and III alpha/beta (ML II and ML III) are lysosomal disorders in which the essential mannose-6-phosphate recognition marker is not synthesized onto lysosomal hydrolases and other glycoproteins. The disorders are caused by mutations in GNPTAB, which encodes two of three subunits of the heterohexameric enzyme, N-acetylglucosamine-1-phosphotransferase ML II, recognizable at birth, often causes intrauterine growth impairment and sometimes the prenatal "Pacman" dysplasia. The main postnatal manifestations of ML II include gradual coarsening of neonatally evident craniofacial features, early cessation of statural growth and neuromotor development, dysostosis multiplex and major morbidity by hardening of soft connective tissue about the joints and in the cardiac valves. Fatal outcome occurs often before or in early childhood. ML III with clinical onset rarely detectable before three years of age, progresses slowly with gradual coarsening of the facial features, growth deficiency, dysostosis multiplex, restriction of movement in all joints before or from adolescence, painful gait impairment by prominent hip disease. Cognitive handicap remains minor or absent even in the adult, often wheelchair-bound patient with variable though significantly reduced life expectancy. As yet, there is no cure for individuals affected by these diseases. So, clinical manifestations and conservative treatment is important. This review aimed to highlight the extra-skeletal clinical problems in ML II and III.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.281-286
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• 2002

To study of binder and fine aggregate a lot of replacement fly-ash concrete, initial characteristics, standard environment of curing temperature $20^{\circ}C$, hot-weather environment of curing temperature $35^{\circ}C$, . Flesh concrete tested slump. air contest and Hardening concrete valuated setting period of form, day of age 1, 3, 5. 7, 10, 28 compression strength in sealing curing. Purpose of study is consultation materials in field that variety of fly-ash replacement concrete mix proportion comparison and valuation. (1) Experiment result age 28day compression strength more higher plan concrete then standard environment in curing temperature $20^{\circ}C$, , most strength F43 is hot-weather environment in curing temperature $35^{\circ}C$, replacement binder 25%, fine aggregate 15%. (2) Hot-weather environment replacement a mount of fly-ash is a same of plan concrete setting period of form. Age 28day compression strength replacement a mount of fly-ash more hot-weather concrete then plan concrete.

• Journal of the Korean Ceramic Society
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• v.22 no.2
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• pp.33-38
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• 1985

The hydration of supersulphated slag cement which is the mixture of granuloated blast furnace slag anhydrite $C_4A_3$ type clinker and calcined dolomite was studied by X-ray diffraction differential thermal analysis scanning electron microscope observation and measurement of the rate of heat liberation. The main hydrates were ettrigite and C-S-H. This supersulphated slag cement enhanced rapid-hardening and increased in strength at early stage due to the much of ettrigite. Furthermore the hardened cement became stronger due to the C-S-H that was produced from the hydration of the $eta$-$C_2S$ in $C_4A_3$ type clinker and the hydration of the dissolved components from slag at later period.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.664-675
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• 2010

Recently environment-friendly construction method is major trend in both domestic and world constrction fields. In this paper High Functional Performance Agent(Hi-FA) which has various improved engineering characteristics different with conventional Portland cement grouting, such as high viscosity, liquidity, void filling ability, early hardening, and separation resistance, was analyzed by field and laboratory test. Also soil improvement and existing deep foundation protection works were performed and analyzed using Hi-FA.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.217-220
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• 2001

Due to the tendency of increase in demolished-concrete produced by alteration and deterioration of concrete structures, recycling of those demolished-concrete is necessary to solve the exhaustion of natural aggregate, in order to save resources and protect environment, especially being want of resources in Korea. For this purpose, concrete made with the pozzolanic cement and recycled aggregate was tested for compressive and tensile strength. The pozzolanic cement was a mixture of OPC(Ordinary Portland Cement) and pozzolans such as fly ash, other siliceous materials and early rapid hardening cement(ERC). It was found that the compressive strength of the pozzolanic cement was enhanced when 0.75% of ERC was dozed, as compared with OPC mortar. It was also shown that compressive and tensile strength of concrete with recycled aggregate and pozzolanic cement were higher than those of concrete with crushed stones and OPC. It was concluded that the pozzolanic cement influenced on the increase of concrete strengths with recycled aggregate.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.148-151
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• 2004

The hardening of concrete after setting is accompanied with nonlinear temperature distribution caused by development of hydration heat of cement. Especially at early ages, this nonlinear distribution has a large influence on the tensile cracking. As a result, in order to predict the exact temperature distribution in concrete structures it is required to examine thermal properties of concrete. In this study, the coefficient of air convection for concrete mix of nuclear power plant, which presents thermal transfer between surface of concrete and air, was experimentally investigated with variables such as velocity of wind and types of form. The coefficient of air convection obtained from experiment increases with velocity of wind, and its dependance on wind velocity is varied with types of form. This tendency is due to a combined heat transfer system of conduction through form and convection to air. The coefficient of air convection for concrete mix of nuclear power plant obtained from this study was well agreed with the existing models.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.421-424
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• 2006

In massive hardening concrete structures, early age thermal cracking due to the heat of hydration may occur. There are many massive structures in Incheon bridge project and they have to be carefully treated to prevent thermal cracking. In this paper, an example of analyzed and measured results of hydration heat of pile caps in the Incheon bridge project was represented. Finite element simulations were carried out before casting and curing method was determined using the analyzed result. Sensors were installed before casting and temperature and strain of concrete was measured during curing. Gathered data were compared with the analyzed data and selected control method to prevent cracking was verified. Analyzed result gave good agreement and very few cracking could be found.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.861-865
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• 2000

During the placement of concrete in cold weather, there are serious problems due to frozen concrete in the early stage. These adverse effects prevent the hardening of concrete. There are special mixing, handling, placement and crying to minimize problems. Heat crying and sheet curing have been used in crying steps in order to reduce problems. However, these curing methods are not efficient because it is hard to obtain the good quality and strength of concrete, and moreover, it needs additional works for curing. In this study, we evaluate the application of cold weather concrete by the dose antifreezing admixture in concrete mix design. Because it is easy to handle inconstruction site and improve the quality of concrete. As the result of this paper is to present a successful case for the practical use of cold weather concrete.

• Journal of the Korean Ceramic Society
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• v.32 no.8
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• pp.873-880
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• 1995

In order to prepare the modified belite (C2S-C4A3S-C4AF-CS) cement with low energy, clinkers were synthesized by converter slag, limestone, gypsum and clay. The synthesized clinkers were characterized and the hydration processes were investigated by XRD, SEM and microconduction calorimetry. The hydrates were mainly C-S-H and ettringite. The needle-like ettringite formed by the hydration of C4A3S at the early stage of hydration was filled in the inner vacant spaces of the hardened body and it might contribute to the rapid-hardening phenomena. The hardened body became stronger due to the hydration of C2S at the later period. The compressive strengths of the cement-3 mortars hydrated for 3, 7 and 28 days were 115, 128 and 211 Kgf/$\textrm{cm}^2$, respectively.