• 자원리싸이클링
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• 제27권3호
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• pp.58-65
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• 2018

국내 순환유동층보일러형 발전소에서 발생하는 석탄재의 재활용을 위해 석회석 미분말과 CFBC 비산재를 이용하여 0.2~0.4 mm 크기를 가지는 석회계 흡수제를 제조하였다. 석회계 흡수제에 소석회를 소량 혼합한 결과 칼슘실리케이트 성분이 입자 표면에 형성되어 강도가 향상되었으며, 탈황특성을 비교한 결과 상업적으로 사용되고 있는 로내탈황용 석회석보다 약 10% 정도 높은 전환율을 가진 것으로 나타나 탈황 흡수제로 활용 가능함을 확인하였다.

• Carbon letters
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• 제24권
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• pp.90-96
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• 2017

We demonstrated the sensitivity of optically active single-walled carbon nanotubes (SWCNTs) with a diameter below 1 nm that were homogeneously dispersed in cement composites under a mechanical load. Deoxyribonucleic acid (DNA) was selected as the dispersing agent to achieve a homogeneous dispersion of SWCNTs in an aqueous solution, and the dispersion state of the SWCNTs were characterized using various optical tools. It was found that the addition of a large amount of DNA prohibited the structural evolution of calcium hydroxide and calcium silicate hydrate. Based on the in-situ Raman and X-ray diffraction studies, it was evident that hydrophilic functional groups within the DNA strongly retarded the hydration reaction. The optimum amount of DNA with respect to the cement was found to be 0.05 wt%. The strong Raman signals coming from the SWCNTs entrapped in the cement composites enabled us to understand their dispersion state within the cement as well as their interfacial interaction. The G and G' bands of the SWCNTs sensitively varied under mechanical compression. Our results indicate that an extremely small amount of SWCNTs can be used as an optical strain sensor if they are homogeneously dispersed within cement composites.

• Advances in materials Research
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• 제4권3호
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• pp.133-144
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• 2015

The aim of this investigation is to prepare geopolymer resin by alkali activation of ceramic waste (AACW) with different sodium hydroxide (NaOH) and liquid sodium silicate (LSS) concentrations. In order to prepare geopolymer cement, AACW was replaced by 10 and 30 % by weight (wt.,) of concrete waste (CoW) as well as 10 and 30 wt., % ground granulated blast-furnace slag (GGBFS). The results showed that, the compressive strength of AACW increases with the increase of activator content up to 15:15 wt., % NaOH: LSS. All AACW hardened specimens activated by 3:3 (MC6), 6:6 (MC12), 12:12 (MC24) and 15:15 wt., % (MC30) NaOH: LSS destroyed when cured in water for 24h. The MC18 mix showed higher resistivity to water curing. The results also showed that, the replacement of AACW containing 9:9 wt., % NaOH: LSS (MC18) by 10 (MCCo10) and 30 (MCCo30) wt., % CoWdecreased the compressive strength at all ages of curing. In contrast, the MCCo10 mix showed the lower chemically combined water content compared to MC18 mix. The MCCo30 mix showed the higher chemically combined water content compared to MC18 and MCCo10 mixes. The compressive strength and chemically combined water of all AACWmixes containing GGBFS (MCS10 and MCS30) were higher than those of AACWwith no GGBFS (MC18). As the amount of GGBFS content increases the chemically combined water increases. The x-ray diffraction (XRD) proved that as the amount of CoWcontent increases, the degree of crystallinity increases. Conversely, the replacement of AACW by GGBFS leads to increase the amorphiticity character. The infrared spectroscopy (FTIR) confirms the higher reactivity of GGBFS compared to CoW as a result of successive hydration products formation, enhancing the compaction of microstructure as observed in scanning electron microscopy (SEM).

• 한국재료학회지
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• 제29권11호
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• pp.727-733
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• 2019

In this study, the glass melting properties are evaluated to examine the possibility of using refused coal ore as replacement for ceramic materials. To fabricate the glass, refused coal ore with calcium carbonate and sodium carbonate in it (which are added as supplementary materials) is put into an alumina crucible, melted at $1,200{\sim}1,500^{\circ}C$ for 1 hr, and then annealed at $600^{\circ}C$ for 2 hrs. We fabricate a black colored glass. The properties of the glass are measured by XRD (X-ray diffractometry) and TG-DTA (thermogravimetry-differential thermal analysis). Glass samples manufactured at more than $1,300^{\circ}C$ with more than 60 % of refused coal ore are found by XRD to be non-crystalline in nature. In the case of the glass sample with 40 % of refused coal ore, from the sample melted at $1,200^{\circ}C$, a sodium aluminum phosphate peak, a disodium calcium silicate peak, and an unknown peak are observed. On the other hand, in the sample melted at $1,300^{\circ}C$, only the sodium aluminum phosphate peak and unknown peak are observed. And, peak changes that affect crystallization of the glass according to melting temperature are found. Therefore, it is concluded that glass with refused coal ore has good melting conditions at more than $1,200^{\circ}C$ and so can be applied to the construction field for materials such as glass tile, foamed glass panels, etc.

• International Journal of Concrete Structures and Materials
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• 제9권2호
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• pp.207-217
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• 2015

The influence of powdered and colloidal nano-silica (NS) on the mechanical properties of cement mortar has been investigated. Powdered-NS (~40 nm) was synthesized by employing the sol-gel method and compared with commercially available colloidal NS (~20 nm). SEM and XRD studies revealed that the powdered-NS is non-agglomerated and amorphous, while colloidal-NS is agglomerated in nature. Further, these nanoparticles were incorporated into cement mortar for evaluating compressive strength, gel/space ratio, portlandite quantification, C-S-H quantification and chloride diffusion. Approximately, 27 and 37 % enhancement in compressive strength was observed using colloidal and powdered-NS, respectively, whereas the same was up to 19 % only when silica fume was used. Gel/space ratio was also determined on the basis of degree of hydration of cement mortar and it increases linearly with the compressive strength. Furthermore, DTG results revealed that lime consumption capacity of powdered-NS is significantly higher than colloidal-NS, which results in the formation of additional calcium-silicate-hydrate (C-S-H). Chloride penetration studies revealed that the powdered-NS significantly reduces the ingress of chloride ion as the microstructure is considerably improved by incorporating into cement mortar.

• Advances in Computational Design
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• 제3권2호
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• pp.147-163
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• 2018

Cementitious composites are multiphase heterogeneous materials with distinct dissimilarity in strength under compression and tension (high under compression and very low under tension). At macro scale, the phenomenon can be well-explained as the material contains physical heterogeneity and pores. But, it is interesting to note that this dissimilarity initiates at molecular level where there is no heterogeneity. In this regard, molecular dynamics based computational investigations are carried out on cement clinkers and calcium silicate hydrate (C-S-H) under tension and compression to trace out the origin of dissimilarity. In the study, effect of strain rate, size of computational volume and presence of un-structured atoms on the obtained response is also investigated. It is identified that certain type of molecular interactions and the molecular structural parameters are responsible for causing the dissimilarity in behavior. Hence, the judiciously modified or tailored molecular structure would not only be able to reduce the extent of dissimilarity, it would also be capable of incorporating the desired properties in heterogeneous composites. The findings of this study would facilitate to take step to scientifically alter the structure of cementitious composites to attain the desired mechanical properties.

• Advances in concrete construction
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• 제7권4호
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• pp.263-275
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• 2019

In the present work, Granulated Blast Furnace Slag (GBFS) and Fly ash (FA) were used as partial replacement of Natural Sand (NS) and Ordinary Portland Cement (OPC) by weight. One control mix, one with GBFS, three with FA and three with GBFS-FA combined mixes were prepared. Replacements were 50% GBFS with NS and 20%, 30% and 40% FA with OPC. Preliminary investigation on development of compressive strength was carried out at 7, 28 and 90 days to ensure sustainability of waste materials in concrete matrix at room temperature. After 90days, thermo-mechanical study was performed on the specimen for a temperature regime of $200^{\circ}-1000^{\circ}C$ followed by furnace cooling. Weight loss, visual inspection along with colour change, residual compressive strength and microstructure analysis were performed to investigate the effect of replacement of GBFS and FA. Although adding waste mineral by-products enhanced the weight loss, their pozzolanicity and formation history at high temperature played a significant role in retaining higher residual compressive strength even up to $800^{\circ}C$. On detail microstructural study, it has been found that addition of FA and GBFS in concrete mix improved the density of concrete by development of extra calcium silicate gel before fire and restricts the development of micro-cracks at high temperature as well. In general, the authors are in favour of combined replacement mix in view of high volume mineral by-products utilization as fire protection.

• 한국환경농학회지
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• 제16권2호
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• pp.175-180
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• 1997

산성비에 의한 작물의 피해경감방안을 구명하고자 pot시험으로 사양토에 콩(단엽콩)을 공시작물로하여 석회물질을 토양(소석회), 엽면(석회유 1%, 석회유 2%), 토양 및 엽면(소석회+석회유 1%, 소석회+석회유 2%)에 처리하고, 인공산성비(pH 2.7)를 10mm씩 2일간격으로 50회 살포한 후 콩의 생육, 수량 및 수량구성요소, 가시적 엽피해율, 엽록소 함량, 광합성 능력, 식물체중 무기성분 함량, 시험후 토양의 이화학적 특성 등을 분석조사한 결과는 다음과 같다. 1. 인공산성비 45회 살포후 경장은 석회유 2%구에서, 엽수는 소석회+석회유 1%구에서 가장 컸으며, 엽폭, 경경, 개체당 분지수는 처리간에 유의성없이 비슷하였다. 인공산성비 살포에 의하여 전처리구에서 종실 수량이 감소하였으나, 석회물질의 처리구에서 종실 수량이 증가하였으나, 특히 소석회+석회유 1%구가 가장 좋았다. 2. 인공산성비 15 및 45회 살포후 엽피해율 경감효과는 석회물질의 시용이 효과적이었다. 3. 인공산성비 45회 살포후 엽록소 함량은 소석회+석회유 1%구에서 가장 높았으며, 인공산성비 30회 살포후 광합성 능력은 소석회구에서 가장 좋았다. 4. 인공산성비 살포로 식물체중 질소, 인산, 황 등의 함량이 증가되었으며, 소석회를 토양에 처리함으로써 식물체중 질소, 카리, 석회 등의 함량이 증가하는 경향이었다. 5. 인공산성비 살포로 토양의 pH는 낮아졌으나, 질소 및 황 함량은 증가되는 경향이었고, 인산, 석회, 카리, 고토등의 함량은 감소되는 경향이었다.

• 한국산학기술학회논문지
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• 제20권12호
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• pp.715-722
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• 2019

콘크리트 구조물은 외부로부터 콘크리트 내부로 침투 및 확산하는 유해 이온(CO₃^2-, Cl^-, SO₄^2- 등)에 의하여 철근의 부식 및 콘크리트 열화가 발생하여 내구성이 저하된다. 따라서 콘크리트의 열화를 방지 또는 지연시키기 위하여 콘크리트 표면 보호용 마감 모르타르의 사용은 매우 중요하다고 할 수 있다. 본 연구에서는 실리카 졸과 칼슘 이온으로 개질한 천연 라텍스 성분을 열화 콘크리트의 보수용 모르타르 또는 콘크리트 표면 보호용 마감 모르타르에 사용할 수 있는 시멘트 모르타르에 사용함으로써 콘크리트의 열화 방지 또는 열화 지연의 가능성에 대해 검토하였다. 연구 결과, 개질 라텍스 성분 중에 함유된 칼슘 이온과 실리카 졸의 성분에 의해 미세한 칼슘 실리케이트 수화물이 시멘트 재료의 공극에 생성되어 시멘트 모르타르의 공극 분포를 감소시켜 유해 이온(CO₃^2-, Cl^-, SO₄^2- 등)의 침투 및 확산을 저감 시키고, 라텍스 성분이 시멘트 경화체의 공극 내부에 존재함으로 내알칼리성 및 중성화 저항성이 향상됨을 확인할 수 있었다.

• 한국토양비료학회지
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• 제14권4호
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• pp.242-249
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• 1982

카드뮴의 해독(害毒)을 경감(輕減)하는데 필요(必要)한 기초지식(基礎知識)을 얻기 위(爲)하여 카드뮴이 처리(處理)된 토양(土壤)에 석회물질(石灰物質)과 개량제(改良劑)를 사용(使用)한 것과 이미 석회(石灰)가 사용(使用)된 토양(土壤)에 Cd를 처리(處理)한 것을 분(盆)에 담아서 1981년(年) 여름 또는 가을에 자연토양수분조건하(自然土壤水分條件下)에 묻고 처리후(處理后) 40일(日)~70일(日)사이에 토양시료(土壤試料)를 채취분석(採取分析)한 결과(結果)는 다음과 같다. 1. 카드뮴은 토양(土壤)을 0.1N-HCl나 2%구연산으로 침출(浸出)했을 때에 많고, $N-AcNH_4$로 침출(浸出)했을때 적었으며 물로 침출(浸出)했을 때는 나오지 않았다. 침출(浸出)된 카드뮴의 처리간(處理間) 차이(差異)는 $N-NH_4A$ 침출(浸出)에서 가장 뚜렷하여 이것을 유효카드뮴으로 할 수 있을 것 같다. 2) 치환성(置換性)카드뮴을 줄이는데 가장 유효한 것은 수산화(水酸化)카드뮴이며 탄산(炭酸)카드뮴, 규산(珪酸)카드뮴의 순서(順序)로 효과가 적어졌다. 3. 과석(過石)도 치환성(置換性)카드뮴을 줄였는데 인산(燐酸)카드뮴을 침전(沈澱)시키기 때문으로 판단(判斷)되었다. 4. 치환성(置換性)카드뮴은 토양(土壤)의 pH 6.0~6.5에서 많고 그 이하(以下)나 이상(以上)에서 적었다. pH 5.0이하(以下)에서는 $Mn^{+{+}}$으로 인(因)한 $Cd^{+{+}}$의 침전(沈澱)때문이고, pH 6.0이상(以上)에서는 수산화(水酸化)카드뮴의 침전(沈澱)때문으로 판단(判斷)되었다.