알칼리금속과 알칼리 토금속 촉매 담지 대나무 활성탄의 NO 가스 반응 특성

박영철 ( Young Cheol Bak ),최주홍 ( Joo Hong Choi ) 한국화학공학회 2016 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.54 No.5

대나무를 원료로 탄화 및 활성화온도 900 oC에서 대나무 활성탄을 만들고, 이 대나무 활성탄에 알칼리 금속(Na, K)과 알칼리토금속(Ca, Mg)을 담지 시켜 알칼리 담지 대나무활성탄을 제조하였다. 제조된 알칼리 담지 활성탄의 비표면적 및 세공분포 등의 물리적 특성을 분석하였다. 또한 폐 대나무활성탄의 재활용을 위하여 알칼리 담지 대나무활성탄과 NO 기체의 반응 특성 실험을 열중량분석기를 사용하여 비등온반응(반응온도 20~850 oC, NO 농도 0.1 kPa)과 등온반응(반응온도 600, 650, 700, 750, 800, 850 oC, NO 농도 0.1~1.8 kPa) 조건에서 하였다. 실험 결과, 대나무 활성탄 특성 분석에서 알칼리 담지 대나무 활성탄에서는 알칼리 담지량이 증가할수록 세공 부피와 표면적이 감소하였다. 비등온과 등온 NO 반응에서는 전체적으로 Ca금속담지 대나무활성탄[BA(Ca)]과 Na금속담지 대나무활성탄[BA(Na)], K금속담지 대나무활성탄[BA(K)], Mg금속담지 대나무활성탄[BA(Mg)]이 대나무활성탄[BA]에 비하여 반응속도가 향상되는 것을 볼 수 있다. BA(Ca)> BA(Na)> BA(K)> BA(Mg)> BA 순으로 촉매 활성이 유효하였다. NO 반응에서의 활성화에너지는 82.87 kJ/mol[BA], 37.85 kJ/mol[BA(Na)], 69.98 kJ/mol[BA(K)], 33.43 kJ/mol[BA(Ca)], 88.90 kJ/mol [BA(Mg)]로 나타났고, NO 분압에 대한 반응차수는 0.76[BA], 0.63[BA(Na)], 0.77[BA(K)], 0.42[BA(Ca)], 0.30[BA(Mg)] 이었다. The impregnated alkali metal (Na, K), and the alkali earth metal (Ca, Mg) activated carbons were produced from the bamboo activated carbon by soaking method of alkali metals and alkali earth metals solution. The carbonization and activation of raw material was conducted at 900 oC. The specific surface area and the pore size distribution of the prepared activated carbons were measured. Also, NO and activated carbon reaction were conducted in a thermogravimetric analyzer in order to use for de-NOx agents of the used activated carbon. Carbon-NO reactions were carried out in the nonisothermal condition (the reaction temperature 20~850 oC, NO 1 kPa) and the isothermal condition (the reaction temperature 600, 650, 700, 750, 800, 850 oC, NO 0.1~1.8 kPa). As results, the specific volume and the surface area of the impregnated alkali bamboo activated carbons were decreased with increasing amounts of the alkali. In the NO reaction, the reaction rate of the impregnated alkali bamboo activated carbons was promoted to compare with that of the bamboo activated carbon [BA] in the order of BA(Ca)> BA(Na)> BA(K)> BA(Mg) > BA. Measured the reaction orders of NO concentration and the activation energy were 0.76[BA], 0.63[BA(Na)], 0.77[BA(K)], 0.4 [BA(Ca)], 0.30 [BA(Mg)], and 82.87 kJ/mol[BA], 37.85 kJ/mol[BA(Na)], 69.98 kJ/mol[BA(K)], 33.43 kJ/mol[B (Ca)], 88.90 kJ/mol [BA(Mg)], respectively.

나트륨계 알칼리 활성화제를 사용한 친환경 알카리활성 슬래그 섬유보강콘크리트 보의 휨성능 평가

하기주,이동렬,하재훈 한국구조물진단유지관리공학회 2015 한국구조물진단유지관리공학회 논문집 Vol.19 No.2

In this study, it was developed eco-friendly alkali-activated slag fiber reinforced concrete using ground granulated blast furnace slag, alkali activator (water glass, sodium hydroxides), and steel fiber. Eight reinforced concrete beam using alkali-activated slag concrete were constructed and tested under monotonic loading. The major variables were mixture ratio of alkali activator, mixed/without of steel fiber. Experimental programs were carried out to improve and evaluate the flexural performance of such test specimens, such as the load-displacement, the failure mode, the maximum load carrying capacity, and ductility capacity. All the specimens were modeled in scale-down size. The reinforced concrete beams using the eco-friendly alkali-activated slag fiber reinforced concrete was failed by the flexure or flexure-shear in general. In addition, the maximum strength increased with the adding the mol of sodium hydroxide, and the specimen reinforced the steel fiber showed the value of maximum strength which is increased by 15.8% through 25.9%. It is thought that eco-friendly alkali-activated slag fiber reinforced concrete can be used with construction material and product to replace normal concrete. If there is applied to structures such as precast concrete member and production of 2nd concrete product, it could be improved the productivity and reduction of construction duration etc. 이 연구에서는 산업부산물인 알카리활성 슬래그와 알칼리 활성화제 (물유리, 수산화나트륨)에 강섬유를 사용하였으며, 이를 철근콘크리트 보에 적용하여 휨성능 평가를 하였다. 주요변수는 알칼리 활성화제의 혼입비율 및 강섬유를 혼입으로 총 8개의 실험체를 제작하였으며, 재료 및 구조성능 평가를 위한 실험을 수행한 결과 다음과 같은 결론을 얻었다. 친환경 알카리활성 슬래그 섬유보강콘크리트를 사용한 철근콘크리트 보는 전반적으로 휨 또는 휨-전단에 의하여 파괴되었다. 그리고 수산화나트륨의 몰 증가와 강섬유를 보강한 결과 최대내력이15.8~25.9% 증가한 값이 나타났으며, 연성 또한 높게 나타났다. 친환경 알카리활성 슬래그 섬유보강콘크리트는 기존의 콘크리트를 대체할수 있는 기초연구로서 향후 건설소재 및 재료분야에 활용할 수 있을 것으로 사료되며, 이러한 특성을 바탕으로 콘크리트 2차 제품 생산과구조부재를 PC화하여 활용할 경우 생산성 향상, 공기단축 등 효율이 상승될 것으로 보인다.

알칼리 자극제의 종류 및 첨가율에 따른무시멘트 경량 경화체의 강도특성

이상수,김윤미,박선규 한국건축시공학회 2014 한국건축시공학회지 Vol.14 No.4

본 연구는 포틀랜드 시멘트를 사용하지 않고 산업부산물인 고로슬래그를 기반으로 제지애시와 알칼리 자극제를 사용하여 기포를 발생시킴으로써 경량 패널의 심재 및 충전재등에 사용할 수 있는 무시멘트 경량 경화체를 개발하고자하였다. 이를 위하여 먼저 제지애시의 적정 치환율을 도출하기 위한 기초실험을 실시하였다. 기초 실험을 바탕으로 제지애시와 반응하여 수소기체를 발생시킬 수 있는 알칼리 자극제의 종류 및 첨가율에 따라 본 실험을 실시하였으며, 제조된 시험체를 대상으로 재령별 겉보기 밀도와 강도를 측정하였다. 그 결과 제지애시의 적정 치환율은 5%이며, 알칼리 자극제는 NaOH를 12.5% 첨가한 경화체의 겉보기 밀도가1.13g/㎤, 감소율 40.45%로 가장 낮은 겉보기 밀도를 나타내었으며, 겉보기 밀도와 비교하여 비교적 높은 강도를 발현하였다. 따라서, 알칼리 자극제로써 NaOH를 적정량 사용하고제지애시와의 반응시간을 늦출 수 있는 방법을 강구한다면보다 높은 강도와 경량성을 겸비한 무시멘트 경량 경화체를제조할 수 있을 것으로 판단된다. In order to reduce the emission of carbon dioxide(CO2), this research use blast furnace slag in concrete manufacture,as 100% replacement of cement. The aim of this study is to investigate the density and strength properties ofalkali-activated lightweight composites with alkali activators of different types and different amounts. The bubble forachieving the lightweight of alkali-activated lightweight composites was generated in the reaction between the paperash and the alkali activators instead of using a foaming agent. Lightweight formed concrete was conducted basicexperimental for determining replacement ratio of paper ash. Then, the density and strength were measured accordingto the types and the contents of the alkali accelerator that can react with the paper ash. As results, the optimumreplacement ratio of the paper ash was 5%. The alkali activator containing NaOH 12.5% obtained the lowest weightof 1.13g/㎤. Also, compressive strength were relatively high. Therefore, this study demonstrated that alkali acceleratorwith a certain amount of NaOH can achieve relatively high strength and lightweight alkali-activated lightweightcomposites.

석고가 첨가된 슬래그 기반 알카리활성 모르터의 압축강도 및 건조수축 변형률

양근혁,심재일 한국건축시공학회 2008 한국건축시공학회지 Vol.8 No.1

Twelve mortars were mixed and tested to explore the effect of gypsum on the compressive strength development and shrinkage strain of alkali-activated mortars. Powder typed sodium silicate and ground granulated blast-furnace slag were employed as alkaline activator and source material, respectively, to produce cementless mortar. The main variables investigated were alkali quality coefficient combining the concentration of activator and main compositions in source material, and the adding amount of gypsum ranged between 1 and 5% with respect to the weight of binder. Initial flow, compressive strength development, modulus of rupture, and shrinkage strain behavior of mortar specimens were measured. In addition, the hydration production of alkali-activated pastes with gypsum was traced using X-ray diffraction and energy-dispersive X-ray analysis combined with scanning electron microscope image. Test results showed that the initial flow of slag-based alkali-activated mortar was little influenced by the adding amount of gypsum. On the other hand, the effect of gypsum on the compressive strength of mortar specimens was dependent on the alkali quality coefficient, indicating that the compressive strength increased with the increase of the adding amount of gypsum until a certain limit, beyond which the strength decreased slowly. Shrinkage strain of mortar tested was little influenced by the adding amount of gypsum because no ettringite as hydration product was generated. However, the adding of gypsum had a beneficial effect on reducing the microcrack in the alkali-activated mortar.

알칼리 활성화제를 첨가한 페로니켈슬래그 혼입 삼성분계 콘크리트의 동결융해 저항성

조원정,박광필,안기용 한국건설순환자원학회 2022 한국건설순환자원학회 논문집 Vol.10 No.2

The present study assessed the micro structure and durability characteristics of ternary blended cement with different types of alkali activators. Ground granulated blast furnace slag(GGBS) and ferronickel slag(FNS) was replaced until 50 % of the weight o f cement. In a dditio n, p otassuim hydro xide a nd s o dium h ydro xide w ere used f o r comparing the pro perties o f different type of alkali activator. Ternary blended cement with alkali activators showed higher peak portlandite peak than that of OPC(Ordinary Portlande Cement) and non activated ternary blended cement. Also, there was no new hydration products in ternary blended cement or/and alkali activators. Based on the mercury intrustion porosimetry(MIP) test result, ternary blended cement increased macro pore while alkali activated ternary blended cement modified pore structure and increased microp pore as compared to OPC as control. Combination with alkali activators is desirable to enhance the compressive strength and freeze thaw resistance.

Structural evolution of binder gel in alkali-activated cements exposed to electrically accelerated leaching conditions

Park, Solmoi,Yoon, H.N.,Seo, Joonho,Lee, H.K.,Jang, Jeong Gook Elsevier 2020 Journal of hazardous materials Vol.387 No.-

<P><B>Abstract</B></P> <P>The structural evolution of a binder gel in alkali-activated cements exposed to accelerated leaching conditions is investigated for the first time. Samples incorporating fly ash and/or slag were synthesized and were exposed to electrically accelerated leaching by applying a current density of 5 A/m<SUP>2</SUP>. The leaching behavior of the samples greatly depended on the binder gel formed in the samples. The N-A-S-H type gel abundant in fly ash-rich samples showed some extent of dissolution upon accelerated leaching, while slag-rich samples underwent hydration of the anhydrous slag after leaching. The obtained results are discussed in view of the degradation of the binder gel induced by accelerated leaching, and their potential performance under repository conditions where groundwater-induced leaching is the main durability concern.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Electrically accelerated leaching tests for alkali-activated materials are conducted for the first time. </LI> <LI> Fly ash samples show significant dissolution of binder gel upon leaching, unlike other samples. </LI> <LI> A low hydraulic property of fly ash prevents further hydration from occurring in contact with water. </LI> <LI> C-A-S-H type gel remains more stable in comparison with N-A-S-H type gel. </LI> <LI> Charge-balancing cations in alkali-activated materials have an important implication for the phase stability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Microstructural, Mechanical, and Durability Related Similarities in Concretes Based on OPC and Alkali-Activated Slag Binders

Kirk Vance,Matthew Aguayo,Akash Dakhane,Deepak Ravikumar,Jitendra Jain,Narayanan Neithalath 한국콘크리트학회 2014 International Journal of Concrete Structures and M Vol.8 No.4

Alkali-activated slag concretes are being extensively researched because of its potential sustainability-related benefits. For such concretes to be implemented in large scale concrete applications such as infrastructural and building elements, it is essential to understand its early and long-term performance characteristics vis-a`-vis conventional ordinary portland cement (OPC) based concretes. This paper presents a comprehensive study of the property and performance features including early-age isothermal calorimetric response, compressive strength development with time, microstructural features such as the pore volume and representative pore size, and accelerated chloride transport resistance of OPC and alkali-activated binder systems. Slag mixtures activated using sodium silicate solution (SiO₂-to-Na₂O ratio or Ms of 1?2) to provide a total alkalinity of 0.05 (Na₂O-tobinder ratio) are compared with OPC mixtures with and without partial cement replacement with Class F fly ash (20 % by mass) or silica fume (6 % by mass). Major similarities are noted between these binder systems for: (1) calorimetric response with respect to the presence of features even though the locations and peaks vary based on Ms, (2) compressive strength and its development, (3) total porosity and pore size, and (4) rapid chloride permeability and non-steady state migration coefficients. Moreover, electrical impedance based circuit models are used to bring out the microstructural features (resistance of the connected pores, and capacitances of the solid phase and pore-solid interface) that are similar in conventional OPC and alkali-activated slag concretes. This study thus demonstrates that performance-equivalent alkali-activated slag systems that are more sustainable from energy and environmental standpoints can be proportioned.

Mechanical Performance of Alkali-activated Stabilized Sandy Soil Reinforced with Glass Wool Residue Microfibers

Mohamad Kianynejad,Mohamad Mohsen Toufigh,Vahid Toufigh 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.2

Alkali-activated binders have been introduced as promising alternatives to conventional binders such as lime and ordinary Portland cement (OPC). However, alkali-activated materials exhibit a brittle behavior and crack formation due to tensile stresses is inevitable. To overcome these limitations, incorporation of fibers into the cementitious matrix is among the well-known techniques to improve the flexural behavior and energy absorption of the corresponding composites. The present study aimed to investigate the feasibility of using reinforced alkali-activated metakaolin as an alternative to common stabilizers to improve the engineering characteristics of sandy soil. Calcium carbide residue (CCR) was used as an alkali activator, and glass wool residue (GWR) microfibers were used as reinforcement elements to maximize waste stream utilization. Unconfined compressive strength (UCS), California bearing ratio (CBR), and three-point bending tests were performed to evaluate the mechanical behavior of the alkali-activated products. Moreover, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were employed to determine the microstructure and elemental composition of these products. The results indicate that the compressive strength and ductile behavior of the stabilized soil samples improved significantly. Furthermore, the SEM/EDX analysis of the reinforced alkali-activated samples revealed the interfacial bond between the microfibers and alkali-activated binding gel, enhancing the mechanical performance between the microfibers and cementitious matrix.

Mechanical properties and durability of alkali-activated slag repair mortars containing silica fume against freeze-thaw cycles and salt scaling attack

Moodi, Faramarz,Norouzi, Sepehr,Dashti, Pooria Techno-Press 2021 Advances in concrete construction Vol.11 No.6

Freeze and thaw phenomena in cold regions are the main cause of severe damage to concrete structures. Alkali-activated slag repair mortars, which are introduced as a suitable material for the replacement of Portland cement, can be used as the protective coating for these damaged structures. The mechanical properties and durability of this coating layer should be studied. In this study, the mechanical properties and durability of alkali-activated slag repair mortars with silica fume (SF) participation as inorganic additives against freeze-thaw and salt scaling attacks have been investigated. In order to evaluate the effects of alkaline activators type, the ratio of these solutions to Pozzolan (Pozz), and the use of SF as a substitute base material, these three factors were considered as the main variables to produce 12 alkali-activated slag mortar mixtures. To investigate their mechanical properties, compressive strength, tensile adhesion strength, and drying shrinkage tests were conducted. Also, mortar specimen length change, compressive strength loss, weight loss, and dynamic elastic modulus were measured to evaluate the durability features against freeze-thaw and salt scaling attacks. According to the results, in addition to higher compressive strength and adhesion resistance of alkali-activated slag repair mortars, these mortars showed at least 30% better durability against freeze-thaw and salt scaling attacks than cement-based repair mortar. Also, alkali-activated slag mixtures containing potassium hydroxide, alkaline solution (AS) to Pozz ratio of 0.7, and SF had the best mechanical properties and frost resistance among all mixtures.

나트륨계 알칼리 활성화제를 사용한 친환경 알카리활성 슬래그 섬유보강콘크리트 보의 휨성능 평가

하기주,이동렬,하재훈 한국구조물진단유지관리공학회 2015 한국구조물진단유지관리공학회 논문집 Vol.19 No.2

In this study, it was developed eco-friendly alkali-activated slag fiber reinforced concrete using ground granulated blast furnace slag, alkali activator (water glass, sodium hydroxides), and steel fiber. Eight reinforced concrete beam using alkali-activated slag concrete were constructed and tested under monotonic loading. The major variables were mixture ratio of alkali activator, mixed/without of steel fiber. Experimental programs were carried out to improve and evaluate the flexural performance of such test specimens, such as the load-displacement, the failure mode, the maximum load carrying capacity, and ductility capacity. All the specimens were modeled in scale-down size. The reinforced concrete beams using the eco-friendly alkali-activated slag fiber reinforced concrete was failed by the flexure or flexure-shear in general. In addition, the maximum strength increased with the adding the mol of sodium hydroxide, and the specimen reinforced the steel fiber showed the value of maximum strength which is increased by 15.8% through 25.9%. It is thought that eco-friendly alkali-activated slag fiber reinforced concrete can be used with construction material and product to replace normal concrete. If there is applied to structures such as precast concrete member and production of 2nd concrete product, it could be improved the productivity and reduction of construction duration etc.