• Journal of the Korean Ceramic Society
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• v.53 no.1
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• pp.116-121
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• 2016

The amount of carbon dioxide ($CO_2$) released while producing building materials is substantial and has been targeted as a leading contributor to global climate change. One of the most typical methods of reducing $CO_2$ in building materials is the addition of slag and fly ash, like pozzolan material another method is to reduce $CO_2$ production by developing carbon negative cement. MgO-based cement from the low-temperature calcination of magnesite required less energy and emitted less $CO_2$ than the manufacturing of Portland cements. It is also believed that adding reactive MgO to Portland-pozzolan cements can improve their performance and also increase their capacity to absorb atmospheric $CO_2$. In this study, basic research on magnesia cement using $MgCO_3$ and magnesium silicate ore (serpentine) as the main starting materials, as well as blast furnace slag for the mineral admixture, was carried out for industrial waste material recycling. In order to increase the overall hydration activity, $MgCl_2$ was also added. In the case of the addition of $MgCl_2$as accelerating admixture, there was a promoting effect on the compressive strength. This was found to be due to the production of needle-like dense Mg-Cl hydrates. Mgnesia cement has a high viscosity due to its high specific surface area therefore, when the PC-based dispersing agent was added at a level of more than 1.0%, it had the effect of improving fluidity. In particular, the addition of $MgCl_2$ in magnesia cement using $MgCO_3$and magnesium silicate ore (serpentine) as main starting materials led to a lower expansion ratio and an increase in the freeze-thaw resistance finally, the addition of $MgCl_2$ as accelerating admixture led to good overall durability.

• Journal of the Korea Concrete Institute
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• v.13 no.2
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• pp.123-129
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• 2001

Pozzolan is to improve the strength and the durability of concrete as a result of the pozzolanic reaction, Broadly speaking, pozzolanic materials can be artificial materials, such as slica fume and fly ash, and natural material, such as rice husk ash, clay, volcanic ash, clayish pozzolan. Hwangtoh is a mineral which belongs to a group of matakaolin, especially halloysite, and the main elements is SiO$_2$, Al$_2$O$_3$, Fe$_2$O$_3$. The purpose of this study is to examine the application of Hwangtoh for the concrete admixtures, the composition of this study is shown as follows. Chapter I is analysis for properties of concrete as the kinds of admixture, and Chapter H is analysis for properties of concrete as the replacement ratio of activated Hwangtoh. As a result of this study, Hwangtoh is found to have high practical use as pozzolanic material, and the pertinent range of replacement ratios of Hwangtoh on cement are 10∼20 %.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.623-631
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• 2018

In this study, the degree of deterioration of concrete was investigated in the laboratory under conditions of carbonation and freeze-thaw cycling, which are the major causes of the deterioration of its performance. In this test, the carbonated concrete was subjected to combined freeze-thaw deterioration tests for up to 300 cycles, and its dynamic elastic modulus and compressive strength were measured. The evaluation of the effect of the water-binder ratio on normal concrete subjected to combined carbonization and freezing-thawing showed that its resistibility against such combined deterioration decreased more rapidly in the concrete with a water-binder ratio of 55 % compared with that having a water-binder ratio of 35 %. In the case where the concrete was blended with a mineral admixture consisting of fly ash and blast furnace slag at the same water-binder ratio, it showed an increase of its resistibility against combined deterioration.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.439-449
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• 2008

Mineral admixtures are used to improve the quality of concrete and to develop sustainability of concrete structures. Supplementary cementitious materials (SCM), such as silica fume (SF), granulated blast furnace slag (GGBS) and pulverized fly ash (PFA), are gradually recognized as useful mineral admixture for producing high performance concrete. The study on ternary blended concrete utilizing mainly three major mineral admixtures is limited and the study on durability and chloride induced corrosion resistance of ternary blended concrete is very few. This study examines the durability characteristics of the ternary blended concrete composed of different amount of the SCM with ordinary Portland concrete and the study experimentally focuses on corrosion resistance evaluation of ternary blended concrete subjected to chloride attack. In this study, 50% replacement ratio of mineral admixture to OPC was used, while series of combination of $20{\sim}40%$ GGBS, $5{\sim}15%$ SF and $10{\sim}45%$ PFA binder were used for chloride corrosion resistance test. This study concerned the durability properties of the ternary blended concrete including the corrosion resistance, chloride binding, chloride transport and acid neutralization capacity. It was found that the ternary blended concrete utilizing the SCM densified the pore structures to lower the rate of chloride transport. Also, increased chloride binding and buffering to acid were observed for the ternary blended concrete with chlorides in cast.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.11a
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• pp.57-61
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• 2005

Cement paste is originally the basic material and crucial factor consisting concrete. This study investigates the relationship between flow apparatuses, which are ring flow(R-F), flow cone(F-C) and mini slump(M-S), in order to estimate the fluidity of cement Paste. For quantitatively evaluating the measured data this study also investigated the calibration of the rheology consistent, such as yield value and plastic viscosity, of cement paste using viscometer For this purpose the present work discussed the influence of 3 type of ordinary portland cement with different companies, affecting the fluidity of cement paste. and it also demonstrated the influence of the various kinds of mineral admixtures, such as fly ash(FA), blast furnace slag(BS) and silica fume(SF) and that of incorporating ratio. The author concluded that using R-F apparatus is the most effective flow test method of cement paste and it is exactly proportional to other apparatus' rheological properties.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.225-226
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• 2021

Recently, environmental problems have emerged as a major issue all over the world due to an increase in carbon dioxide(CO₂). The amount of CO₂ generated during cement production accounts for 6% to 8% of domestic CO₂ emissions and a solution to reduce CO₂ emissions the construction industry is trying to use mineral admixtures to reduce cement. Since digestion has no firing process the advantage of it is that there is no air pollution to occur. In this study, we studied the compressive strength of binary non-cement mortar containing rice husk powder extracted from digestion by the ratio of 10%, 20%, 30%, 40%. As a result, the table flow was increased when the mixing rate of rice husk powder extracted from digestion was higher, and the highest compressive strength was shown when the rice husk powder extracted from digestion mixing rate was 10%.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.759-764
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• 2004

In this study, the experiment was carried out to investigate and analyze the ready-mixed concrete production of ultra-high strength concrete with mixing strength of $100N/mm^2$ according to types of mineral admixtures. The main experimental variables were water/binder ratio $25.0\%$, water content $160kg/m^3$ and mineral admixtures such as fly ash, silica fume and meta kaolin. According to the test results, the principle conclusions are summarized as follows. 1) even if it secures similar slump, the viscosity appear to difference by mixing condition relatively. 2) The autogeneous shrinkage of ultra-high strength concrete is profitable that use admixture, and heat of hydration is desirable that apply considering countermeasure enough in the advance. 3) The concrete that use SF10+MK10 on 56days could confirm that it is possible that achieve compressive strength more than $100N/mm^2$ under mixing conditions that is appearing by compressive strength $102.7N/mm^2$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.2
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• pp.75-81
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• 2010

In this study, when concrete properties are changed by concrete mix proportions or blending of admixtures, the characteristics of electro-chemical method for corrosion assessment of the embedded steel are compared and its causes are analyzed. According to the results, when the ratio of corroding area was less than 10%, the half-cell method was affected by concrete properties. In the case of specimen blended admixtures, it is possible to assess the high-corroded steel qualitatively using the half-cell method. For the polarization resistance method, though the corroding area was less than 10%, it has not affected by concrete properties. However, in case of specimen blended admixtures, the corrosion level of steel was underestimated than OPC specimens having a similar corroding area.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.785-793
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• 2003

This study is intended to analyze the effectiveness of expansive additive, shrinkage reducing agent and combination of the two to reduce the autogenous and drying shrinkage of high performance concrete using mineral admixture such as fly ash, blast furnace slag powder and silica fume. According to results, when expansive additive and shrinkage reducing agent are mixed within an appropriate mixing ratio, fluidity and air content are not influenced, and the enhancement of compressive strength is favorable at the age of 91 and 180days. At the mixing ratio of expansive additive of 5% and 10%, the autogenous and drying shrinkage is reduced by 32∼68% and 25∼49% respectively in comparison with plain concrete. And they are reduced by 18∼34% and 16∼26% respectively at the mixing ratio of shrinkage reducing agent of 0.5% and 1.0%, compared with plain concrete. The mixture of EA-SR combined with expansive additive and shrinkage reducing agent is most effective for reduction of shrinkage. Therefore, it is considered that the using method in combination with expansive additive and shrinkage reducing agent is effective to reduce the shrinkage of high performance concrete using mineral admixture such as fly ash, blast slag powder and silica fume.

• Journal of the Korea Institute of Building Construction
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• v.15 no.6
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• pp.597-605
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• 2015

The method of concrete mix design used in this study aims to achieve the identical specified design strength, applying different types and replacement ratio of mineral admixtures and afterwards, fire tests were conducted using the standard time-temperature curve specified in the ASTM E119 to identify the influences of the types of mineral admixtures on the fire resistance performance of high strength concrete(HSC). The least spalling was observed in the test specimen containing blast furnace slag as a partial replacement of cement, while the most significant spalling phenomena were observed in the blast furnace slag test specimen that silica-fume was added in. In particular, the reasonable volume of spalling was observed when solely replaced by silica fume. However, the influence of the cement replacement by silica fume and blast furnace slag on the increases of spalling can be explained through blocked pores by the fine particles of silica fume, leading to decreases in permeability.