• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.97-98
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• 2022

In this study, conducted a Mock-up test on the use of TBC and CGS fine aggregates for the purpose of reducing the upper and lower hydration heat according to the horizontal division and punching of mass concrete. As a result of the experiment, it is judged that it will be effective in preventing temperature cracking of mass concrete when mixing the upper and lower parts and replacing CGS.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.677-680
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• 2008

The surface of particles was energetically modified by inter-grinding OPC and BFS in vibration mill for improvement of the early strength and low-heat evolution of concretes. BFS was pre-grinding in ball-mill to 2535(BS2) and 3245 $cm^2/g$(BS3), in blaine surface area. The inter-grinding time in vibration mill was changed from 10 minutes to 30 minutes. And Mixing ration of BFS to OPC was changed in 60, 70, 80%. After inter-grinding, the change of specific surface area, particle size distribution, hydration heat of cement and compressive strength of mortar were measured. As the result of comparison test with LHC, it was found that the mixture and inter-grinding time satisfying the value of over 100% of compressive strength for 7 days and under 170J/g of heat of hydration for 72 hours. and it was confirmed that the possibility of low heat slag cement utilizing blast furnace slag(BS2, BS3) with the low fineness in high volumes.

• Journal of the Korea Concrete Institute
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• v.17 no.2 s.86
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• pp.293-302
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• 2005

This study describes data from determination of the optimum mix proportion and site application of the mass concrete placed in bottom slab and side wall having a large depth and section as main structures of LNG in-ground tank. This concrete requires low heat hydration, excellent balance between workability and consistency because concreting work of LNG in-ground tank is usually classified by under-pumping, adaptation of longer vertical and horizontal pumping line than ordinary pumping condition. For this purpose, low heat Portland cement and lime stone powder as cementitious materials are selected and design factors including unit cement and water content, water-binder ratio, fine aggregate ratio and adiabatic temperature rising are tested in the laboratory and batch plant. As experimental results, the optimum unit cement and water content are selected under $270kg/m^3$ and $l55{\~}l60 kg/m^3$ separately to control adiabatic temperature rising below $30^{\circ}C$ and to improve properties of the fresh and hardened concrete. Also, considering test results of the confined water ratio($\beta$p) and deformable coefficient(Ep), $30\%$ of lime stone powder by cement weight is selected as the optimum replacement ratio. After mix proportions of 5cases are tested and compared the adiabatic temperature rising($Q^{\infty}$, r), tensile and compressive strength, modulus of elasticity, teases satisfied with the required performances are chosen as the optimum mix design proportions of the side wall and bottom slab concrete. $Q^{\infty}$ and r are proved smaller than those of another project. Before application in the site, properties of the fresh concrete and actual mixing time by its ampere load are checked in the batch plant. Based on the results of this study, the optimum mix proportions of the massive concrete are applied successfully to the bottom slab and side wall in LNG in-ground tank.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.55-56
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• 2011

This study is to investigate the engineering properties of low heat concrete incorporating improved ternary blended cement by combining OPC(original portland cement), blast furnace slag and fly ash. The results were summarized as following ; For ITB(Improved Ternary Blend)mixture was that setting time proved to be accelerated, and adiabatic temperature rises were low. The use of ITB resulted in an increase of initial compressive strength.

• Tunnel and Underground Space
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• v.21 no.4
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• pp.297-306
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• 2011

In this paper, we performed thermodynamic energy balance analysis of the underground lined rock cavern for compressed air energy storage (CAES) using the results of multi-phase heat flow analysis to simulate complex groundwater-compressed air flow around the cavern as well as heat transfer to concrete linings and surrounding rock mass. Our energy balance analysis demonstrated that the energy loss for a daily compression and decompression cycle predominantly depends on the energy loss by heat conduction to the concrete linings and surrounding rock mass for a sufficiently air-tight system with low permeability of the concrete linings. Overall energy efficiency of the underground lined rock caverns for CAES was sensitive to air injection temperature, and the energy loss by heat conduction can be minimized by keeping the air injection temperature closer to the ambient temperature of the surroundings. In such a case, almost all the heat loss during compression phase was gained back in a subsequent decompression phase. Meanwhile, the influence of heat conductivity of the concrete linings to energy efficiency was negligible.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.687-690
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• 2005

Recently, to consider financial and constructive aspect, usage of Admixture, like Blast- Furnace Slag and Fly-Ash, are increased. These mineral admixtures, a by-product of steel industry, have many advantage, to reduce the heat of hydration, increase in ultimate strength, improve workability and etc. But it also reduces early-age strength, so it is prevented from using of Blast-Furnace Slag at cold-weather-concrete. In this study, for the purpose of increasing usage of mineral admixtures, like Blast-Furnace Slag and Fly ash, it is investigated the strength properties of concrete subjected to under low temperature According to this study, if early curing is carried out before having frost damage, the strength of concrete, subjected to frost damage, is recovered. And to consider increasing effect of strength, it is more effective to use of mineral admixtures, especially to use blast furance slag.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.165-168
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• 2005

This paper investigated the effect of W/C and the kinds of cement on the chloride invasion resistance of the offshore concrete. W/C set up 0.30, 0.35, 0.40 and The kinds of cement were used four(ordinary portland cement, ground granulated blast-furnace slag cement, belite cement, low heat portland cement). For the electrical migration test, NT BUILD 492's method was used to estimate the migration coefficient of chloride ion. As a result, the migration coefficients of chloride ion of concrete according to w/c were shown reducing with the w/c increasing, and according to kinds of cement were shown discrepancy in chloride invasion resistance. Especially blast-furnace slag cement was most low it. In the each cement, the compressive strength was shown related to the migration coefficient.

• Advances in concrete construction
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• v.5 no.4
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• pp.377-390
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• 2017

This study proposes a mix design method for geopolymer concrete (GPC) using low calcium fly ash and alccofine, with the focus on achieving the required compressive strength and workability at heat and ambient curing. Key factors identified and nine mixes with varied fly ash content (350, 375 and $400kg/m^3$) and different molarity (8, 12 and 16M) of NaOH solutions were prepared. The cubes prepared were cured at different temperatures ($27^{\circ}C$, $60^{\circ}C$ and $90^{\circ}C$) and tested for its compressive strength after 3, 7 and 28 days of curing. Fly ash content has been considered as the direct measure of workability and strength. The suggested mix design approach has been verified with the help of the example and targets well the requirements of fresh and hardened concrete.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.766-771
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• 2016

This study examined the long-term durability of PC boxes, which was manufactured by low-carbon eco-friendly concrete using an alternative binder to cement and alternative fine aggregate to sand and microwave heat curing system to reduce the construction cost of a near-surface transit system. Based on the test results, the initial compressive strength of microwave heat cured concrete was higher than that of the steam cured concrete, but those were similar in the long-term age. In addition, there was no significant difference between the two curing conditions in the chemical resistance and the freeze-thawing resistance, and the chloride ion penetration level of the concrete cured by two methods was very low. Therefore, low-carbon eco-friendly concrete and microwave heat curing technology are expected to contribute to the economic construction of a near-surface transit system, and reduce carbon dioxide emissions and environmental impact.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.1-7
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• 2020

GGBFS(Ground Granulated Blast Furnace Slag) is one of the most actively used mineral admixtures with excellent long-aged strength and chloride diffusion resistance. Unlike Standard covering GGBFS in Japan and the U.K., the domestic standard for GGBFS does not contain low fineness of GGBFS under 4000 grade. In this paper, several basic tests are carried out for the concrete with 3,000 grade GGBFS concrete and ternary blended concrete for reducing hydration heat by mixing 4,000 grade GGBFS and fly ash, such as fresh concrete properties, compressive strength, and shrinkage properties. The air content and slump between the ternary blended concrete and the concrete with low-fineness GGBFS showed the similar level, and the results of difference in setting time from them were less than 20 minutes, showing no significant difference. In the evaluation of compressive strength and shrinkage characteristics, the ternary blended concrete showed lower long-aged strength and higher shrinkage than the low-fineness GGBFS concrete.