• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.99-102
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• 1999

In the study, the effect of the replacement content(20, 40, 60, 80%) and particle fineness and the chemical activator of the fly-ash on the flow and strength development of mortar was investigated. We found that the higher raito of the fly-ash replacement produced the lower the mortar strength and the higher fineness of the fly-ash yielded the higher strength. Also, we used Na2SO4 as activator of fly-ash to rise compressive strength mortar. The result as follows: the fly-ash mortar which stimulated by chemical activator, was higher strength development at early than the fly-ash mortar without chemical activator. But in the late age, the result indicated adversely.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 춘계 학술논문 발표대회 1부
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• pp.89-91
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• 2011

This paper is to investigate experimentally the property of strength development on the concrete for 5 years according to the change of a replacement rate of coarse particle cement in order to use coarse particle cement with a fineness of 1 900 ㎠/g that is classified during a grinding process of the OPC production. The result is that as the CC replacement rate increased, the compressive strength was decreased proportionally. but the width of strength reduction was reduced as time passed.

• 방사성폐기물학회지
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• 제7권2호
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• pp.79-86
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• 2009

원자력시설의 콘크리트 폐기물은 서로 다른 메카니즘에 의해 다양한 핵종에 의해 방사화 되거나 오염된다. 우라늄 변환시설 및 연구로 해체 시 발생된 오염된 콘크리트의 부피감용을 위해 가열 분쇄 실험에 의해 자갈, 모래, 페이스트의 골재의 크기에 따른 핵종의 분배특성에 대해 고찰하였다. 실험결과 대부분의 방사성 핵종은 골재로부터 제거되어 페이스트에 존재하였으며 특히, 가열 온도는 방사성 핵종을 오염된 콘크리트 폐기물로부터 분리하는데 중요한 변수로 확인되었다. 즉, 콘크리트 표면에 오염된 물질은 밀도가 높은 자갈, 모래보다는 다공성 물질의 페이스트에 농축되었다. 방사화 콘크리트에서는 80%, 우라늄 변환시설의 콘크리트 폐기물에서는 약 75% 정도의 부피감용을 얻었다.

• 한국건축시공학회지
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• 제2권2호
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• pp.129-134
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• 2002

The strength and durability of concrete are affected by various factors such as the quality of material, mixing ratio, construction, the method of cure, time elapsed. the condition of test and etc., it is very difficult to pre-estimate the strength of concrete with the use of experimental specimen. The domestic standard of specimen cylindrical type and its sizes are both l0cm$\times$20cm and 15cm$\times$30cm, which are prescribed in KS F2405, and the loading speed is prescribed to test with 2~3kgf/$\textrm{cm}^2$ per second. The loading speed should have great effect on the compressive strength, but in reality in the construction site sometimes the loading speed is applied so dubiously that the value of the compressive strength can be unreliable. And the cross sectional area of a specimen should be level and smooth, otherwise it can be broken at a lower stress than the real strength through the eccentric or intensive working of the load. Capping should be carried out in order to measure the strength correctly. And used for capping are various materials such as capping compound, cement glue, plaster, mechanical grinding and etc. In this study, therefore, I have carried out an experiment on the relationship among the loading speed, the ratio of height to diameter of specimen, the method of capping, and the compressive strength, for the efficient quality control of concrete structures. So this study has been purposed to provide some basic data that can be used effectively at construction sites.

• Computers and Concrete
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• 제20권2호
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• pp.197-204
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• 2017

Typically, high lime fly ash (Class C) has been characterized as a fly ash, which at lower replacement levels is not as effective as the low lime (Class F) fly ash, in mitigating alkali-silica reaction (ASR) in portland cement concrete. The influence of fineness of Class C, obtained by grinding virgin fly ash into finer particles, on its pozzolanic reactivity and ASR mitigation performance was investigated in this study. In order to assess the pozzolanic reactivity of mortar mixtures containing virgin or ground fly ashes, the strength activity index (SAI) test and thermo-gravimetric analysis (TGA) were conducted on the mortar cubes and paste samples, respectively, containing virgin fly ash or two ground fly ashes. In addition, to evaluate any improvement in the ASR mitigation of ground fly ashes compared to that of the virgin fly ash, the accelerated mortar bar test (AMBT) was conducted on the mortar mixtures containing different dosages of either virgin or ground fly ashes. In all tests crushed glass aggregate was used as a highly reactive aggregate. Results from this study showed that the finest fly ash (i.e., with an average particle size of 3.1 microns) could increase the flow ability along with the pozzolanic reactivity of the mortar mixture. However, results from this study suggested that the fineness of high lime fly ash does not seem to have any significant effect on ASR mitigation.

• 한국세라믹학회지
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• 제53권4호
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• pp.435-443
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• 2016

Coal ash, a material generated from coal-fired power plants, can be classified as fly ash and bottom ash. The amount of domestic fly ash generation is almost 6.84 million tons per year, while the amount of bottom ash generation is 1.51 million tons. The fly ash is commonly used as a concrete admixture and a subsidiary raw material in cement fabrication process. And some amount of bottom ash is used as a material for embankment and block. However, the recyclable amount of the ash is limited since it could cause deterioration of physical properties. In Korea, the ashes are simply mixed and used as a replacement material for cement. In this study, an attempt was made to mechanically activate the ash by grinding process in order to increase recycling rates of the fly ash. Activated fly ash was prepared by controlling the mill types and the milling times and characteristics of the mortar containing the activated fly ash was analyzed. When the ash was ground by using a vibratory mill, physical properties of the mortar mixed with such fly ash were higher than the mortar mixed with fly ash ground by a planetary mill.

• Computers and Concrete
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• 제11권1호
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• pp.39-49
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• 2013

The use of ground fly ash in concrete can increase the risk of slump loss due to the drastic surface change of the particles after the grinding treatment and the accelerated reaction compared to the untreated ash. This study is aimed at the early age hydration and time-dependent rheology changes of cement paste containing ground fly ash. An original fly ash is ground into different fineness and the hydration of cement paste containing the ground fly ash is monitored with the ultrasound propagation method. The zeta potentials of the solid particles are measured and the changes of rheological parameters of the cement pastes with time are analyzed with a rheometer. A particle packing model is used to probe packing of the solid particles. The results show that the early age hydration of the paste is strongly promoted by replacing Portland cement with fly ash up to 30 percent (by mass), causing increase of the yield stress of the paste. The viscosity of a paste containing ground fly ash is lower than that containing the untreated ash, which is explained by the denser packing of the solid particles.

• 한국건축시공학회지
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• 제10권6호
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• pp.145-154
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• 2010

As buildings have become higher and larger, the use of high performance concrete has increased. With this increase, interest in and use of ultra fine powder admixture is also on the rise. The silica fume and BSF are the admixtures currently being used in Korea. However, silica fume is exclusively import dependent because it is not produced in Korea. In the case of BFS, it greatly improves concrete fluidity and long-term strength. But a problem exists in securing early strength. Furthermore, air-cooled slag is being discarded, buried in landfills, or used as road bed materials because of its low activation energy. Therefore, we investigated in this study the usability of nano-slag (both rapidly-chilled and air-cooled) as an alternative material to the silica fume. We conducted a physic-chemical analysis for the nano-slag powder and performed a mortar test to propose quality standards. The analysis and testing were done to find out the industrial usefulness of the BFS that has been grinded to the nano-level.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.27-28
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• 2020

In this study, as a measure to recycle red mud, which is a byproduct of the Bayer Process, red mud was manufactured as liquid and recycled without drying and grinding. Previous studies have shown that mechanical performance decreases when liquid red mud is applied to cement concrete. Therefore, in this study, liquid red mud was neutralized with nitric acid and applied to cement paste to examine the properties of cement paste according to the addition of red mud. As a result, the compressive strength of 10% liquid red mud decreased by 37.7% compared to Plain, and 10% liquid red mud indicates similar strength to Plain and restores the strength.

• 한국도로학회논문집
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• 제13권2호
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• pp.115-123
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• 2011

본 연구는 도심지 버스전용차로의 교차로 구간 아스팔트 포장을 프리캐스트 패널을 이용하여 강성 포장으로 교체하는 조립식 포장 시공을 수행한 후 이러한 포장의 초기 거동 및 공용성을 분석하기 위해 수행되었다. 조사 항목으로는 차량 진출입 구간에서 아스팔트 포장과 프리캐스트 패널과의 단차, 프리캐스트 패널간의 단차 및 줄눈 간격, 프리캐스트 패널의 침하, 패널 표면의 미끄럼저항 성능등을 선정하였다. 시공 후 일정시간이 지난 후에 다이아몬드 그라인딩 공법을 적용하여 이의 효과도 분석하였다. 추적조사 결과 시간이 경과함에 따라 프리캐스트 패널의 단차, 줄눈 간격, 침하, 미끄럼저항 등은 거의 변화가 없었으며, 이로 인해 프리캐스트 패널이 안정되게 하중을 지지하고 있다는 것을 알 수 있었다. 또한 다이아몬드 그라인딩 공법의 적용은 프리캐스트 패널의 단차 감소를 가져오는 것으로 확인되었다.