• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.423-424
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• 2009

The use of fly-ash has been being increased to prevent alkali-aggregate reaction in concrete and to reuse industrial by-product. However the absorption of unburnt carbon to cement particles due to the increase of fly-ash usage decreases air content result in the risk at durability due to free-thawing. The properties of entrained air in fresh concrete, with various fly-ash replacement ratios and different types of air entraining agents, have been analyzed to suggest basic data for the stable air entraining property with large amount of fly-ash replacement in concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.206-207
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• 2018

This study is a series of studies intended to derive the improvement of strength concrete quality using an emulsified refined oil (ERCO). In other words, ERCO is used to analyze the improvement degree of the basic properties of ordinary strength concrete by pre-adding the AE Agent on its products. ERCO was also planned to have a mixing ratio of 0, 0.5 %, and the pre-addtion of AE agent mixed with 0, 1, 2, and 3 % of the concrete's mixed ERCO mass. As a result, as the pre-injection of AE agent was increased, the slump, and air contents tended to be improved microscopically, but there was no significant effect. and Compressive strength tends to increase smart-all as the pre-addtion of AE agent increases in concrete, but it does not have a significant effect.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.565-568
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• 2008

Domestic area of most be happened chloride deicer damage. Because daily mean temperature is below 0$^{\circ}C$ from the area of domestic most. Concrete durability influence Air Content. Presently, We used to AE(air-entraining agent) for increase freeze-thaw durability. So, on concrete Air Spacing ratio used $200{\mu}m{\sim}230{\mu}m$ in Canada and under $250{\mu}m$ in Japan institution. Use of Air content has been and will continue to be a major part of concrete durability and scaling. Chloride-containing chemicals such as calcium chloride or rock salt are main deicers for the road. The prepared optimum mix concrete in this study show that freeze-thaw and scaling resistance of Non-AE(air content 1.5%) and AE (air content 4.5%, 7.2%). Solution concentrations of deicing agent were good result, and the pore system and change of hydration products is not difference comparing before freeze-thaw test.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.97-98
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• 2023

In this study, comparison of the quality standard of chemical admixtures between Korea and China is conducted. It is classified into three types of water reducing agents: standard, delayed, and accelerated according to the sensitivity and strength improvement of the sensitivity and strength of the agent. However, Chinese standards classify reducing agents only as standard, high efficiency, and high performance, and do not add AE agents into water reducing agent. On the other hand, that of Korea has a classification regulation for reducing agents added with AE agents.

• Journal of the Korea Concrete Institute
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• v.25 no.3
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• pp.321-329
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• 2013

Recently, the medium-low level radioactive waste from nuclear power plant must be transported from temporary storage to the final repository. Medium-low level radioactive waste, which is composed mainly of the liquid ion exchange resin, has been consolidated with cementitious material in the plastic or iron container. Since cementitious material is brittle, it would generate cracks by impact load during transportation, signifying leakage of radioactive ray. In order to design the safety transporting equipment, there is a need to check the compressive strength of the current waste. However, because it is impossible to measure strength by direct method due to leakage of radioactive ray, we will estimate the strength indirectly by the dynamic modulus of elasticity. Therefore, it must be identified the relationship between of strength and dynamic modulus of elasticity. According to the waste acceptance criteria, the compressive strength of cement based solid is defined as more than 3.44 MPa (500 psi). Compressive strength of the present solid is likely to be significantly higher than this baseline because of continuous hydration of cement during long period. On this background, we have tried to produce the specimens of the 28 day's compressive strength of 3 to 30 MPa having the same material composition as the solid product for the medium-low level radioactive waste, and analyze the relationship between the strength and the dynamic modulus of elasticity. By controling the addition rates of AE agent, we made the mixture containing the ion exchange resin and showing the target compressive strength (3~30 MPa). The dynamic modulus of elasticity of this mixtures is 4.1~10.2 GPa, about 20 GPa lower in the equivalent compressive strength level than that of ordinary concrete, and increasing the discrepancy according to increase strength. The compressive strength and the dynamic modulus of elasticity show the liner relationship.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.299-306
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• 2016

In this research, influence of low quality aggregate on engineering properties of concrete was evaluated experimentally. From the experiment, the fresh properties of slump and air content were controlled with unit water and AE dosage and all mixture were designed to have similar fresh properties of slump and air content with various quality of aggregate. Under this conditions, comparing with the mixture with high quality aggregate, the mixture with low quality aggregate showed the unit water and AE dosage were increased about 18 and 98%, respectively, because of poor grading and quantity of fines. For compressive strength, the low quality aggregate, specifically, exploded debris, clay sand, and sea sand contributed on decreasing compressive strength about 20~35%. Additionally, the concrete mixture including low quality fine and coarse aggregate showed adverse quality in not only compressive strength but also durability of freeze-thawing resistance, drying shrinkage, carbonation, and chloride ingression. Therefore, it is considered that for low quality aggregate, extra treatment processes such as washing or controlling gradation, and regulation to limit the use of low quality aggregate are needed.

• Magazine of the Korea Concrete Institute
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• v.10 no.1
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• pp.125-132
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• 1998

경량골재 콘크리트의 내구성과 경제성에 대한 인식 부족으로 조경재료나 인공토양 둥 구조부재 이외의 분야에 사용되고 있는 국내 실정에 비해서, 구미 여러나라에서는 고강도 경량골재를 장지간 교량과 고충건물에 사용하고 있다. 경량골재 콘크리트는 구조물의 재료비 단순비교에 있어서도 경제성이 있을 뿐만 아니라, 자중감소로 인한 구조적, 기하학적 장점도 있으며, 또한 고강도 경량골재의 개발로 경량골재가 가지고 있는 여러 문제점을 해소하여 사용성과 내구성에 있어서 보통골재 콘크리트와 큰 차이가 없는 상황이다. 그러나국내에서 생산된 경량골재는 닫힌 공극보다 열린 공극을 많이 내포하고 있어 수분흡수가 많고, 특히, 동결융해에 대한 내구성에 취약한 문제점을 가지고 있다. 본 논문에서는 내동해성 향상을 위해 10종류의 고강도 경량골재 콘크리트 공시체를 제작하여 실리카 흄, 물.시멘트비, AE제, 강섬유 등을 실험 변수로 하여동결융해 실험을 수행하였다. 연구결과 실리카흄, 물.시멘트 비는 어느 정도 내동해성을 향상시키지만 근본적인 해결방안이 되지 못하며, AE제를 첨가한 공시체와 강섬유를 사용한 공시체는 동결융해 내구성 지수가 90%이상으로 측정되어 내동해성을 개선시킬 수 있는 요소로 나타났다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.117-124
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• 1988

From the test results of the adsorption characteristics of AE admixture, it was shown that the adsorption of AE admixture on fly ash was mearly completed in 30 minutes and the higher was ignition loss, the larger the quantity of saturation adsorption. Because most of the ignition loss of the fly ash was due to the unburned carbon, it could be said that the unburned carbon is the main reason of reduction of air content in AE concrete. On the other hand, in the case of superplasticizer, the amount of saturation adsorption in fly ash was lower than in cement and the same result was obtained in the dispersive effect. But, when using superplasticizer in fly ash substituting concrete, the fludity in the concrete was not decreased.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2022.10a
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• pp.301-302
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• 2022

최근 들어 염해, 콘크리트의 탄산화, 동결융해 등의 열화요인 의하여 발생할 수 있는 콘크리트의 내구성에 대한 다양한 연구가 진행되고 있는데, 이러한 열화요인은 독립적이 아닌 복합열화의 형태로 작용하게 되는데, 열화현상을 저감하는 한 방편으로 플라이애쉬와 같은 혼화재를 사용하디도 한다. 플라이애쉬는 유동성 증진을 통한 내구성의 향상과, 수화열 저감을 통한 균열감소 및 장기강도 증진 등의 효과가 있으며, 시멘트를 대체함으로써 경제적인 효과를 유발하는 장점도 가지고 있다. 그러나 플라이애쉬는 품질편차가 크고, 경우에 따라서 미연탄소분에 의한 AE제 흡착 등으로 인한 콘크리트의 내구성 및 강도를 저하시킬 수 있는 요소를 내포하고 있으므로 사용 시 주의가 필요하다. 본 연구에서는 열화를 저감하고, 내구성을 갖는 고강도 콘크리트를 제조하기 위하여 다양한 배합비의 플라이애쉬 혼입 콘크리트를 실험한 후 그 결과를 분석·고찰함으로써 내구성 콘크리트의 제작 시 혼화재로서의 적용성 및 타당성을 검증하고자 하며, 플라이애쉬를 내구성 재료로 그 활용을 극대화하고, 다양한 플라이애쉬의 사용량과 물/결합재비(W/B)에 대하여 내구성이 높은 고강도 콘크리트 제조방법을 범용화하며, 그 품질을 평가하는 것을 목적으로 한다.

• Journal of the Korea Institute of Building Construction
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• v.12 no.3
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• pp.284-290
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• 2012

Cement Fineness Modulus (CFM) is a method of expressing the distribution of particle sizes of cement in numeric form. If CFM is controlled through crush process of cement without modifying the chemical components or mineral composition of cement, it is judged to be able to produce a cement satisfying various requirements because it is estimated to enable various approaches to cement such as high early strength, moderate heat, low heat cement and so on. Therefore, in this study, as basic research for manufacturing special cement utilizing the controls of CFM, the intention was to review the impacts of CFM on the fundamental properties of concrete. To summarize the result, as mixture characteristics of fresh concrete, ratio of small aggregate and unit quantity were gradually increased, securing greater fluidity, with an increase in CFM, while the amount of AE and SP were reduced gradually. In addition, setting time was delayed as CFM increased. Furthermore, compression strength was relatively high during initial aging as CFM became smaller, but as time passed, compression strength became smaller, and it showed the same level of strength as aging time passed about three years.