• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2019년도 춘계 학술논문 발표대회
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• pp.207-208
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• 2019

In this study, compressive strength was measured to evaluate the initial strength of cement mortar substituted with coal gasification slag containing desulfurized gypsum, and the reactivity of desulfurized gypsum was confirmed. In order to improve the reactivity, 2% gypsum mixed type and gypsum unfedged type specimens were fabricated and the influence of desulfurization gypsum on compressive strength of coal gasification slag and blast furnace slag fine powder replacement cement mortar was compared and confirmed. As a result of the experiment, it was confirmed that the initial compressive strength of the specimen containing the desulfurized gypsum was improved at the initial stage.

• 한국세라믹학회지
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• 제53권3호
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• pp.354-361
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• 2016

The purpose of this study was to prepare lightweight foamed concrete by mixing coal fly ash of circulating fluidized bed combustion(CFBC) with cement, and to develop uses for recycling by analyzing carbonation behavior resulting from a change in conditions for pressurized carbonation. For concrete, CFBC coal fly ash was mixed with Portland cement to the water-binder ratio of 0.5, and aging was applied at room temperature after 3 days of curing at $20^{\circ}C$, RH 60%. For carbonation, temperature was fixed at $60^{\circ}C$ and time at 1 h in the use of autoclave. Pressures were controlled to be $5kgf/cm^2$ and the supercritical condition of $80kgf/cm^2$, and gas compositions were employed as $CO_2$ 100% and $CO_2$ 15%+N2 85%. In the characteristics of produced lightweight concrete, the characteristics of lightweight foamed concrete resulting from carbonation reaction were affirmed through rate of weight change, carbonation depth test, air permeability, and processing analysis for the day 28 specimen. Based on these results, it is concluded that the present approach could provide a viable method for mass production of eco-friendly lightweight foamed concrete from CFBC coal fly ash stabilized by carbonation.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2019년도 추계 학술논문 발표대회
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• pp.166-167
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• 2019

In this study, to test the performance of concrete used as a concrete admixture as a recycling method of CGS, gypsum was mixed and the chloride ion penetration resistance test of CGS and BFS substituted concrete was conducted. As a result, it was found that without gypsum type test specimen, the CGS sustituted test specimens had lower chloride ion penetration resistance than the BFS substituted specimens. When gypsum was added, it was confirmed that the chloride ion penetration resistance was poor regardless of the type of admixture. In addition, it was confirmed that both admixtures were less resistant to chloride ion penetration than OPC, regardless of the presence of gypsum. However, considering the uneven quality variation of coal, which greatly affects the quality of CGS, further research is needed.

• Geomechanics and Engineering
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• 제15권4호
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• pp.1017-1027
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• 2018

To explore the influence of coal thickness on the mechanical behavior and the failure characteristics of rock-coal-rock (RCR) mass, the experimental investigation of uniaxial compressive tests was conducted first and then a systematic numerical simulation by particle flow code (PFC2D) was performed to deeply analyze the failure mechanical behavior of RCR specimens with different coal thicknesses in conventional compression tests. The overall elastic modulus and peak stress of RCR specimens lie between the rock and the coal. Inter-particle properties were calibrated to match the physical sample strength and the stiffness response. Numerical simulation results show that the deformation and strength behaviors of RCR specimens depend not only on the coal thickness, but also on the confining pressure. Under low confining pressures, the overall failure mechanism of RCR specimen is the serious damage of coal section when the coal thickness is smaller than 30 mm, but it is shear failure of coal section when the coal thickness is larger than 30 mm. Whereas under high confining pressures, obvious shear bands exist in both the coal section and the rock section when the coal thickness is larger than 30 mm, but when the coal thickness is smaller than 30mm, the failure mechanism is serious damage of coal section and shear failure of rock section.

• Composites Research
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• 제34권1호
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• pp.51-56
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• 2021

석탄 핏치의 전구체인 콜타르를 바인더 및 함침재로 이용하여 벌크흑연을 제조할 수 있는 가능성을 검토하고자 하였다. 충전재로 천연흑연을 이용하였으며, 천연흑연과 콜타르를 혼합 및 성형한 후 탄화 열처리를 실시하였다. 탄화 열처리 후 함침-재탄화를 5회 실시하여 밀도, 기공율, 압축강도, 그리고 이방성비를 측정하였다. 탄화체의 최고 밀도는 1.76 g/㎤였고, 기공율은 최소 15.6%로써 공정 제어에 의해 조절이 가능하였다. 압축강도는 최고 20.3 MPa이 얻어졌다. 탄화체의 이방비는 최대 0.34로써 강한 이방성 탄화체를 얻을 수 있었다. 따라서 콜타르를 바인더 및 함침재로 이용하여 벌크 형태의 인조흑연 제조가 가능하다는 것을 확인하였다. 또한 탄화체의 이방성을 조절하여 전기적, 기계적 방향 특성을 조절한다면 적절한 재료 설계를 통하여 다양한 분야에 응용할 수 있을 것이라 판단된다.

• 한국결정성장학회지
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• 제28권5호
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• pp.199-205
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• 2018

IGCC(integrated gasification combined cycle) 발전소에서 발생된 석탄회로부터 발포 및 비발포 지오폴리머를 제조하고, 그 내수성을 평가하였다. 시편을 30일간 물에 침지하여 미세구조 변화 및 침지액의 알칼리도 변화를 측정함에 있어 지오폴리머 발포여부, 상온재령 조건, 그리고 침지시간을 변수로 실험하였다. Si-sludge를 0.1 wt% 첨가한 지오폴리머에는 직경이 1~3 mm인 기공들이 발생하여 우수한 발포성을 보였고, calcium-silicate-hydrate 결정상이 생성되었다. 침지실험에서 침지액의 pH가 시간에 따라 증가하는 것은 경화제로 사용된 알칼리 활성화제 중에서 미반응된 것이 물에 녹아나왔기 때문이다. 침지액의 pH 변화로부터 발포된 시편이 제조과정에서 비발포 시편에 비해 지오폴리머 반응이 더 빨리 완결됨을 알 수 있었다. 본 연구를 통하여 IGCC 석탄회를 재활용한 발포 및 비발포 지오폴리머를 성공적으로 제조할 수 있었으며, 향후 내수성이 필요한 분야에 IGCC 석탄회 기반 지오폴리머를 적용하기 위해 필수적인 상온재령 시간, 발포/비발포 유무, 침지 시간 등에 대한 공정 데이터들을 확보하였다.

• Geomechanics and Engineering
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• 제31권4호
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• pp.365-373
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• 2022

In order to investigate the damage evolution law of rock specimens under cyclic loading, cyclic loading tests under constant loads with different amplitudes were carried out on limestone specimens with high strength and brittleness values using acoustic emission (AE) technology and the energy evolution and AE characteristics were evaluated. Based on dissipated energy density and AE counts, the damage variable of specimen was characterized and two damage evolution processes were analyzed and compared. The obtained results showed that the change of AE counts was closely related to radial deformation. Higher cyclic loading values result in more significant radial strain of limestone specimen and larger accumulative AE counts of cyclic loading segment, which indicated Felicity effect. Regarding dissipated energy density, the damage of limestone specimen was defined without considering the influence of radial deformation, which made the damage value of cyclic loading segment higher at lower amplitude loads. The damage of cyclic loading segment was increased with the magnitude of load. When dissipated energy density was applied to define damage, the damage value at unloading segment was smaller than that of AE counts. Under higher cyclic loading values, rocks show obvious damage during both loading and unloading processes. Therefore, during deep rock excavation, the damages caused by the deformation recovery of unloading rocks could not be ignored when considering the damage caused by abutment pressure.

• Geomechanics and Engineering
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• 제24권6호
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• pp.519-529
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• 2021

In coal mining activities, the abutment stress of the coal has to undergo cyclic loading and unloading, affecting the strength and seepage characteristics of coal; additionally, it can cause dynamic disasters, posing a major challenge for the safety of coal mine production. To improve the understanding of the dynamic disaster mechanism of gas outburst and rock burst coupling, triaxial devices are applied to axial pressure cyclic loading-unloading tests under different axial stress peaks and different pore pressures. The existing empirical formula is use to perform a non-linear regression fitting on the relationship between stress and permeability, and the damage rate of permeability is introduced to analyze the change in permeability. The results show that the permeability curve obtained had "memory", and the peak stress was lower than the conventional loading path. The permeability curve and the volume strain curve show a clear symmetrical relationship, being the former in the form of a negative power function. Owing to the influence of irreversible deformation, the permeability difference and the damage of permeability mainly occur in the initial stage of loading-unloading, and both decrease as the number of cycles of loading-unloading increase. At the end of the first cycle and the second cycle, the permeability decreased in the range of 5.777 - 8.421 % and 4.311-8.713 %, respectively. The permeability decreases with an increase in the axial stress peak, and the damage rate shows the opposite trend. Under the same conditions, the permeability of methane is always lower than that of helium, and it shows a V-shape change trend with increasing methane pressures, and the permeability of the specimen was 3 MPa > 1 MPa > 2 MPa.

• 공업화학
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• 제2권4호
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• pp.393-398
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• 1991

실제 실험 시간에 따른 시료의 무게변화와 생성가스의 조성 측정을 동시에 진행할 수 있는 실험실 규모의 장치를 칸 발란스를 이용하여 제작하였다. 급속 가열이 가능하도록 텅스텐 할로겐 등을 이용한 복사가열 방식을 채택하였고 시료 접시는 복사열을 충분히 흡수하도록 흑연을 사용하였다. 석탄가스화 실험조건에서 이 흑연이 반응기체와 반응하는 것을 막기위하여 실리콘나이트로 코팅하였고, 시료접시 바로 밑에 위치한 열전쌍에도 같은 방식으로 제작된 흑연 모자를 씌워 복사열 흡수능력이 서로 다른 흑연(시료접시)과 금속체(열전쌍) 사이에서 생길 수 있는 온도 측정의 오차를 최소화 하도록 하였다. 이 장치를 사용한 결과 상온에서 섭씨 800도까지 3 분 이내에 온도상승이 가능하였으며 시료 접시의 무게변화없이 실험중 석탄 시료의 무게 변화와 가스조성을 동시에 측정할 수 있었다.

• 한국세라믹학회지
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• 제47권2호
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• pp.151-156
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• 2010

Porous mullite/alumina composites have been fabricated by a freeze casting technique using TBA-based coal fly ash/alumina slurry. After sintering, unidirectional macropore channels aligned regularly along the TBA ice growth direction were developed; simultaneously, small sized micropores fromed in the outer walls of the pore channels. The physical and mechanical properties (e.g. porosity and compressive strength) of the sintered porous composites were roughly dependant of processing conditions, due to the complexity of the factors affecting them. However, with increasing solid loading and sintering temperature, the compressive strength generally increased and the porosity decreased. After sintering $1500^{\circ}C$ for 2 h, the porous specimen (porosity: 52.1%) showed a maximum compressive strength of 70.0 MPa.