• 한국건축시공학회지
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• 제17권1호
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• pp.23-30
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• 2017

순환골재가 복토 및 성토용으로 활용되는 경우 순환골재 표면의 미수화 시멘트로부터 발생하는 높은 pH의 침출수는 환경에 큰 영향을 주는 요소이다. 본 연구에서는 이러한 높은 pH의 침출수를 방지하기 위해 순환골재의 효율적인 알칼리 제거 방안에 대해 실험적으로 비교분석 하였다. 실험결과 순환골재의 높은 알칼리성을 감소시키기 위해서는 단순 야적 및 물을 이용한 씻기 방법보다는 비료를 사용한 처리방법이 가장 유리한 것으로 나타났다. 또한, 본 연구에서는 비료의 종류인 인산암모늄과 이인산암모늄을 활용하여 순환골재를 중화시켰고 그 결과 약 3주 만에 pH 8의 중성에 가까운 순환잔골재를 얻을 수 있었다. 본 연구를 통해 순환골재를 토공사용으로 사용할 때에 보다 환경에 안전한 지속가능한 재료로서 활용하는 데에 기여할 것으로 예상한다.

• International Journal of Concrete Structures and Materials
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• 제18권1E호
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• pp.63-70
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• 2006

This study tested the alkali-silica reactivity of various types of crushed stones, following the specifications of ASTM C 227 and C 1260, and the results obtained from the tests were compared. This study also analyzed the effects of particle size and grading of reactive aggregate based on the expansion of mortar-bar due to an alkali-silica. The effect of mineral admixtures to reduce the detrimental expansion caused by the alkali-silica reaction was investigated based on the method specified by ASTM C 1260. The mineral admixtures used in this study were fly ash, silica fume, metakaolin and ground granulated blast furnace slag. The replacement ratios of 0, 5, 10, 15, 25 and 35% were uniformly applied to all the mineral admixtures, and the replacement ratios of 45 and 55% were additionally applied for the admixtures that could sustain the workability at these ratios. The results indicate that replacement ratios of 25% for fly ash, 10% for silica fume, 25% for metakaolin and 35% for ground granulated blast furnace slag were the most effective in reducing the expansion due to the alkali-silica reaction under the experimental conditions of this study.

• Structural Engineering and Mechanics
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• 제83권1호
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• pp.79-92
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• 2022

In this paper, the impact of a vernacular pozzolanic kaolinite mine on concrete alkali-silica reaction and strength has been evaluated. For making the samples, kaolinite powder with various levels has been used in the quality specification test of aggregates based on the ASTM C1260 standard in order to investigate the effect of kaolinite particles on reducing the reaction of the mortar bars. The compressive strength, X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) experiments have been performed on concrete specimens. The obtained results show that addition of kaolinite powder to concrete will cause a pozzolanic reaction and decrease the permeability of concrete samples comparing to the reference concrete specimen. Further, various machine learning methods have been used to predict ASR-induced expansion per different amounts of kaolinite. In the process of modeling methods, optimal method is considered to have the lowest mean square error (MSE) simultaneous to having the highest correlation coefficient (R). Therefore, to evaluate the efficiency of the proposed model, the results of the support vector machine (SVM) method were compared with the decision tree method, regression analysis and neural network algorithm. The results of comparison of forecasting tools showed that support vector machines have outperformed the results of other methods. Therefore, the support vector machine method can be mentioned as an effective approach to predict ASR-induced expansion.

• KCI Concrete Journal
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• 제14권2호
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• pp.76-80
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• 2002

The role of high volume Class F fly ash in reducing expansion due to Alkali-Silica Reaction (ASR) was investigated. A series of modified ASTM C 1260 tests were performed under three different levels of NaOH normality, extending the test period to 28 days, using high- or low alkali cement, and Class F fly ash up to 58 ％ by mass of cement. A reactive siliceous fine aggregate was used. The test results confirm that HVFA replacement in a cementitious system significantly helps in controlling expansion caused by ASR.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.613-616
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• 2008

최근 결합재로 시멘트를 사용하지 않은 알칼리 활성 콘크리트에 대한 연구가 활발히 진행되고 있다. 이 알칼리 활성 콘크리트는 시멘트 대신에 실리콘(Si)과 알루미늄(Al)이 풍부한 플라이애시와 고로슬래그등을 사용하여 알칼리 용액으로 활성화시킨 시멘트 ZERO 콘크리트로서 CO$_2$ 가스를 저감하는데 효과적이다. 본 연구에서는 시멘트를 전혀 사용하지 않고 결합재로서 고로슬래그를 100% 사용한 알칼리 활성 콘크리트를 개발할 목적으로 감수제, 알칼리 활성화제 및 양생조건이 모르타르의 시공성 및 압축강도에 미치는 영향에 대해 검토하였다. 그 결과, NaOH의 몰 농도가 증가함에 따라 유동성은 저하되나, 9M까지는 유동성 저하가 크지 않고, 대부분의 감수제는 유동성 향상에 기여하지 못하는 것으로 나타났다. 그리고 압축강도는 NaOH의 몰 농도가 증가함에 따라 향상되나, 9M이 가장 효율적인 것으로 나타났다. 또한 양생온도 및 양생조건은 고로슬래그 알칼리 활성 모르타르의 강도에는 큰 영향이 없는 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.695-702
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• 2002

Shotcrete (or Sprayed concrete) has been used as an important support material in New Austrian Tunnelling Method (NATM). Since the mid of 1990, permanent shotcrete tunnel linings such as Single-shell, NMT (Norwegian Method of Tunnelling) has been constructed in many countries for reducing the construction time and lowing construction costs instead of conventional in-situ concrete linings. Among essential technologies for successful application of permanent shotcrcte linings, high performance shotcrete providing high strength, high durability, better pumpability has to be developed in advance as an integral component. This paper presents the Ideas and first experimental attempts to increase early strength and bond strength of wet-mixed Steel Fiber Reinforced Shotcrete(SFRS) in sump water condition. In order to increase early strength, a new approach using high-early strength cement with liquid alkali-free accelerator has been investigated From the results, wet-mix SFRS with high-early strength cement and alkali-free accelerator exhibited excellent early strength improvement compared to the ordinary portland content and good bond strength even under sump water condition.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.427-427
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• 2016

Organic-inorganic hybrid perovskite have attracted significant attention as a new revolutionary light absorber for photovoltaic device due to its remarkable characteristics such as long charge diffusion lengths (100-1000nm), low recombination rate, and high extinction coefficient. Recently, power conversion efficiency of perovskite solar cell is above 20% that is approached to crystalline silicon solar cells. Planar heterojunction perovskite solar cells have simple device structure and can be fabricated low temperature process due to absence of mesoporous scaffold that should be annealed over 500 oC. However, in the planar structure, controlling perovskite film qualities such as crystallinity and coverage is important for high performances. Those controlling methods in one-step deposition have been reported such as adding additive, solvent-engineering, using anti-solvent, for pin-hole free perovskite layer to reduce shunting paths connecting between electron transport layer and hole transport layer. Here, we studied the effect of alkali metal halide to control the fabrication process of perovskite film. During the morphology determination step, alkali metal halides can affect film morphologies by intercalating with PbI2 layer and reducing $CH3NH3PbI3{\cdot}DMF$ intermediate phase resulting in needle shape morphology. As types of alkali metal ions, the diverse grain sizes of film were observed due to different crystallization rate depending on the size of alkali metal ions. The pin-hole free perovskite film was obtained with this method, and the resulting perovskite solar cells showed higher performance as > 10% of power conversion efficiency in large size perovskite solar cell as $5{\times}5cm$. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma optical emission spectrometry (ICP-OES) are analyzed to prove the mechanism of perovskite film formation with alkali metal halides.

• Asian-Australasian Journal of Animal Sciences
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• 제19권12호
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• pp.1776-1783
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• 2006

Despite being a rich source of protein (28-34%), karanj (Pongamia glabra) cake is found to be bitter in taste and toxic in nature owing to the presence of flavonoid (karanjin), tannin and trypsin inhibitor, thereby restricting its safe inclusion in poultry rations. Feeding of karanj cake at higher levels (>10%) adversely affected the growth performance of poultry due to the presence of these toxic factors. Therefore, efforts were made to detoxify karanj cake by various physico-chemical methods such as dry heat, water washing, pressure cooking, alkali and acid treatments and microbiological treatment with Sacchraromyces cerevisiae (strain S-49). The level of residual karanjin in raw and variously processed cake was quantified by high performance liquid chromatography and tannin and trypsin inhibitor was quantified by titrametric and colorimetric methods, respectively. The karanjin, tannin and trypsin inhibitor levels in such solvent and expeller pressed karanj cake were 0.132, 3.766 and 6.550 and 0.324, 3.172 and 8.513%, respectively. Pressure-cooking of solvent extracted karanj cake (SKC) substantially reduced the karanjin content at a cake:water ratio of 1:0.5 with 30-minute cooking. Among chemical methods, 1.5% (w/w) NaOH was very effective in reducing the karanjin content. $Ca(OH)_2$ treatment was also equally effective in karanjin reduction, but at a higher concentration of 3.0% (w/w). A similar trend was noticed with respect to treatment of expeller pressed karanj cake (EKC). Pressure cooking of EKC was effective in reducing the karanjin level of the cake. Among chemical methods alkali treatment [2% (w/w) NaOH] substantially reduced the karanjin levels of the cake. Other methods such as water washing, dry heat, HCl, glacial acetic acid, urea-ammoniation, combined acid and alkali, and microbiological treatments marginally reduced the karanjin concentration of SKC and EKC. Treatment of both SKC and EKC with 1.5% and 2.0% NaOH (w/w) was the most effective method in reducing the tannin content. Among the various methods of detoxification, dry heat, pressure cooking and microbiological treatment with Saccharomyces cerevisiae were substantially effective in reducing the trypsin inhibitor activity in both SKC and EKC. Based on reduction in karanjin, in addition to tannin and trypsin inhibitor activity, detoxification of SKC with either 1.5% NaOH or 3% $Ca(OH)_2$, w/w) and with 2% NaOH were more effective. Despite the effectiveness of pressure cooking in reducing the karanjin content, it could not be recommended for detoxification because of the practical difficulties in adopting the technology as well as for economic considerations.

• 한국건설순환자원학회논문집
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• 제5권2호
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• pp.160-167
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• 2017

본 연구에서는 알칼리 활성화 결합재 및 순환골재를 동시에 활용한 100% 순환자원 보투수성 알칼리 결합재 블록의 개발 가능성을 확인하고자 한다. 또한, 공극률, 압축강도, 투수계수, 보수량, 흡수율 및 증발성 등의 특성 시험 방법을 정립하여 표준화의 기초단계를 확보하였다. 그 결과, 순환골재를 이용한 알칼리 활성화 결합재 블록은 액상 규산나트륨 및 초기고온양생을 통해 24MPa급의 보투수성 블록을 제조할 수 있었다. 또한 순환골재를 적용한 경우 천연골재보다 보투수 블록의 보수량, 흡수율 및 상대흡수율에서 효과적인 결과가 나타났다. 종합적으로, 알칼리 활성화 결합재를 기반으로 순환골재 및 액상폴리머를 사용할 경우 보수량, 흡수율 및 상대흡수율 증진이 가능하고 일반 콘크리트 인터로킹 블록과 비교해 약 10% 수준의 표면온도 저감효과를 가진 보투수성 블록의 제조를 기대할 수 있다.

• 한국건축시공학회지
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• 제10권1호
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• pp.39-47
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• 2010

플라이애시는 콘크리트의 특성 개선, 콘크리트 제품의 가격 저감 및 내구성 개선, 수화열 감소 등의 이점이 있으나 다량 첨가시 콘크리트의 강도 부족 및 AE제 사용량의 증가 등으로 인하여 그 사용량이 제한되고 있다. 이에 본 연구에서는 플라이애시의 고부가 가치적 활용을 목적으로 플라이애시의 고분말도화($4000{\sim}8000cm^2/g$), 양생방법, 알카리자극제의 첨가 등을 통하여 플라이애시의 대량 사용에 대한 문제점을 해결하고자 하였으며, 연구결과 플라이애시의 분말도를 높여 양생온도 $40^{\circ}C$전후로 하여 자극제 첨가율을 적정하게 사용할 경우 수화물이 안정한 상태로 되어 강도발현이 아주 우수하게 나타나, 이에 대한 연구가 지속될 경우 플라이애쉬의 다량치환에 대한 효과적 가치 창출이 가능할 것으로 사료된다.