• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.55-56
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• 2022

Recently, water leak is increasing due to poor compaction or segregation of concrete on external wall. In addition, the flatness quality of the slab is lowered due to the deterioration of the workability of concrete. In this study, the performance of high fluidity concrete of 21MPa using a polycarboxylate-based superplasticizer was evaluated to improve the compaction and quality of the concrete wall.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.3
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• pp.122-129
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• 2016

In this study, we developed a pressing device which can reproduce the pressure of concrete inside the conveying pipe as a part of the basic study to development of high fluidity concrete under high pressure pumping. Using this pressing device, we evaluated a absorption properties of aggregate that are crushed coarse aggregate, river gravel and lightweight coarse aggregate according to pressure of coarse aggregate and aggregate inside a high fluidity concrete, focused on the reduction of unit water quantity by pressure. In addition, it was evaluated the compressive strength of high fluidity concrete about before and after of pressive. Test a result, case of condition under the high pressure of 250 bar, absorption ratio of crushed coarse aggregate and river gravel were not increased above the surface absorption, absorption ratio of lightweight coarse aggregate was increased than the surface absorption.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.04a
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• pp.25-28
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• 2007

In this study we measured the changes according to time respectively on the basis of 0, 30, 60 and 90 minutes, taking into consideration the decline in fluidity of concrete according to elapsed time to analyze manufacturing capability of batcher plant according to elapsed time of ready-mixed concrete manufactured in batcher plant, and offer basic data for mixture design of ultra-high strength concrete. The proportion of water-binder was 23.55, water content was 160kg/m3, proportion of replacement of crushed sand was 0, 20 and 40% at 3 level, and we applied to the same condition of triaxial component using blast furnace slag powder and silica fume as admixture. And to meet the demand of certain fluidity, we measured respectively on property before and after hardening of ultra-high strength concrete using superplasticizer. As a result of experiment, before hardening of ultra-high strength concrete showed the best fluidity in conditions of crushed sand replacement rates of 20% and superplasticizer composition of 1.95%, but it appeared that fluidity drops as time goes by in the same composition condition. And it appeared that when it comes to hardened, the changes of compression strength according to elapsed time by crushed sand replacement rates were within 1MPa. Therefore, it turned out that the difference of strength according to elapsed time was low and compression strength of 280dys in composition mentioned above appeared highly as 88MPa.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.140-141
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• 2018

There are three types of high fluidity concrete: powder based, VMA based, and combined. In the case of the powder based high fluidity concrete mixture, according to the textbook, increased viscosity due to the replaced fly ash can prevent segregation of coarse aggregate. On the other hand, decreased density of the powder due to the fly ash replacement can causes segregation but there is no report on this issue. Therefore, in this research, the segregation resistance and segregation evaluation method for powder based high fluid concrete mixture are evaluated. As a result, with increased replacing ration of supplementary materials, EIS value was decreased and apparently segregation resistance was increased. However, from the compressive strength evaluation depending on height of the cylindrical specimen, it was confirmed that the different of strength difference between top and bottom part of the specimen. Thus, following research regarding vertical segregation should be studied.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.835-840
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• 2000

The purpose of this study is developing concrete Mixing & placing method that could be adjusted to vertical joint at top-down method. Basic test was consists of general, high fluidity, and high quality mixing concretes and Mock-up test had several placing ways, placing positions. They were examined several placing ways, placing positions with Mock-up model comparison with three mixing concrete to know fluidity characterics. Used with Mock-up model to know packing ability from placing ways and positions. The result of the study like this; High fluidity and High quality concretes show favorable packing ability, especially, in sheath placing way. It was expected to good result in next planned real structure test.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.157-158
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• 2018

In this study, the current tendency to replace a large amount of material admixture, which is fly ash (FA) and blast furnace slag (BS), into concrete is that high-grade cheese high admixture of high fluidity concrete In consideration of the substitution rate, we considered J-Ring to investigate the influence on the segregation resistance and the method of evaluating the classical segregation. In addition to the admixture replacement rate in the study results, the EIS using J-Ring became lower and the percentage of vehicles with segregation increased. Such a tendency is considered to be positive when J-Ring is used when segregation is judged if segregation degree is similar to EIS using J-Ring.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.11a
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• pp.75-78
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• 2007

The steel slag, a by-product which is produced by refining pig iron during the manufacture of steel, is mainly used as road materials after aging. It is necessary to age steel slag for long time in air because the reaction with water and free-CaO in steel slag could make the expansion of volume. This problem prevents steel slag from being used as aggregate for concrete. However, steel slag used in this study was controled by a air-jet method which rapidly cools substance melted at a high temperature. The rapidly-chilled method would prevent from generation of free-CaO in steel slag. Also, Molten steel slag rapidly-chilled by air in high speed becomes a fine aggregate of nearly spherical shape. This study dealt with the influence of the using rate of rapidly-chilled steel slag and polymer resin on fluidity of polymer concrete, as a results Since RCSS has spherical shape and high density, up to replacement ratio of 100%, increases concrete fluidity under same polymer content and decrease polymer content in order to secure the same fluidity

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.605-608
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• 1999

In this paper, the application of limestone grain, which produced by being gathered electrically in the process of manufacturing of cement, to high fluidity concrete are investigated. High fluidity mortar is used for this experiment. According to the experimental results, especially, high viscosity and the loss of air content are accomplished by applying limestone grain as the partial substitution of fine aggregates. In case of hardened mortar, high strength development at early age can be achieved by using limestone grain. But excessive dosage of limestone grain can cause high drying shrinkage.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.23-28
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• 1998

In this paper, the compensation of the shrinkage in high performance concrete by applying CSA expansive additives are discussed. According to toe experimental results, fluidity and strength decrease with the increase of the dosage of expansive additives. When 5% of expansive additive are mixed, not only high fluidity and strength, but also the compensation of drying-shrinkage can be achieved.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.689-696
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• 2017

The practical applications of ordinary high-fluidity concrete have been limited due to several drawbacks, such as high hydration heat, high amount of shrinkage, and non-economic strength development. On the other hand, due to its advantages, such as improvement of construction quality, reduction of construction cost and period, the development of high-fluidity concrete is a pressing need. This study examined the properties of high-fluidity concrete, which can be manufactured on the low binders using a viscosity agent to prevent the segregation of materials. The optimal viscosity agent was selected by an evaluation of the mechanical properties of high-fluidity concrete among six viscosity agents. The acrylic type and urethane type viscosity agents showed the best performance within the range where no material separation occurred. The mechanical properties were evaluated to examine the optimal amount of AC and UT viscosity agent added by mixing two viscosity agents according to the adding ratio and blending them together with high performance water reducing agent. When the ratio of the AC : UT viscosity agents was 5:5, it was most suited for high-fluidity concrete with low binders by increasing the workability and effect of the reducing viscosity.