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Onutai S, Sato J, Osugi T. Possible pathway of zeolite formation through alkali activation chemistry of metakaolin for geopolymer–zeolite composite materials: ATR-FTIR study. J SOLID STATE CHEM 2022. [DOI: 10.1016/j.jssc.2022.123808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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2
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Imaizumi A, Nakada A, Matsumoto T, Yokoi T, Chang HC. Synthesis of Microporous Aluminosilicate by Direct Thermal Activation of Phenyl-Substituted Single-Source Aluminosilicate Molecular Precursors. Inorg Chem 2022; 61:13481-13496. [PMID: 35976816 DOI: 10.1021/acs.inorgchem.2c02006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The construction of aluminosilicates from versatile molecular precursors (MPs) represents a promising alternative strategy to conventional processes based on monomeric molecular or polymeric Al and Si sources. However, the use of MPs often suffers from drawbacks such as the decomposition of the core structures in the presence of solvents, acids, or bases. In this work, we demonstrate a simple thermal synthesis of porous aluminosilicates from single-source spiro-7-type MPs that consist of a tetrahedral Al atom and six Si atoms functionalized with 12 phenyl (Ph) groups, (C+)[Al{Ph2Si(OSiPh2O)2}2]- (C+[AlSi6]-; C+ = pyridinium cation (PyH+), Na+, K+, Rb+, or Cs+), without using a solvent or activator. Microporous aluminosilicates synthesized via the thermal treatment of C+[AlSi6]- under a 79% N2 + 21% O2 atmosphere exhibited extremely low carbon contents (0.10-1.28%), together with Si/Al ratios of 3.9-6.7 ± 0.2 and surface areas of 103.1-246.3 m2/g. The solid-state 27Al and 29Si MAS NMR spectra suggest that the obtained aluminosilicates with alkali cations retain a tetrahedral Al site derived from the spiro-7-type core structure. After a proton-exchange reaction, the aluminosilicates showed almost 1.5 times higher reactivity in the catalytic ring-opening of styrene oxide than the aluminosilicate before proton exchange due to the catalytically active OH site being predominantly bridged by tetrahedral Al and Si atoms. These results suggest that the present MP strategy is a promising method for the introduction of key structures into active inorganic materials.
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Affiliation(s)
- Akira Imaizumi
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
| | - Akinobu Nakada
- Department of Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.,Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Takeshi Matsumoto
- Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan
| | - Toshiyuki Yokoi
- Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan.,Tokyo Tech World Research Hub Initiative (WRHI), Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan
| | - Ho-Chol Chang
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
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Microstructure properties of poly(phospho-siloxo) geopolymeric network with metakaolin as sole binder reinforced with n-SiO2 and n-Al2O3. J SOLID STATE CHEM 2022. [DOI: 10.1016/j.jssc.2022.123188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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4
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Abdelrahman O, Garg N. Impact of Na/Al Ratio on the Extent of Alkali-Activation Reaction: Non-linearity and Diminishing Returns. Front Chem 2022; 9:806532. [PMID: 35047482 PMCID: PMC8761903 DOI: 10.3389/fchem.2021.806532] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 12/10/2021] [Indexed: 11/13/2022] Open
Abstract
To address the high CO2 footprint associated with cement production, many alternative, sustainable binders are now gaining worldwide attention-including alkali-activated materials. The alkali-activation reaction of metakaolin is a fairly complex process involving transformation of one amorphous reactant (precursor metakaolin) into another amorphous product or products (N-A-S-H gel and/or disordered zeolite type phases). In spite of this complexity, researchers in the past 2 decades have gained significant knowledge on the nature of this reaction at multiple scales. Understanding and developing a clear relationship between the alkalinity of the mix and the extent of reaction is of high interest for practical applications. However, detailed and thorough investigations on this important relationship are limited. Here, in this study, we address this gap by systematically investigating a series of alkali-activated materials samples with a wide range of Na/Al ratios (0.5-1.8) using seven different yet complementary analytical techniques (isothermal calorimetry, FTIR, XRD, TGA, NMR, and Raman imaging). Applied in tandem, these tools reveal a clear but non-linear relationship between the Na/Al ratio and the extent of alkali-activation reaction indicating diminishing returns at higher Na/Al ratios, where higher Na/Al ratios cause an increase in the degree of reaction until a certain point at which the increase in Na/Al ratio does not significantly affect the reaction kinetics, but may affect the gel polymerization. These findings could potentially aid decision making for commercial applications of AAMs where alkalinity of the mix is an important parameter for performance as well as safety.
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Affiliation(s)
- Omar Abdelrahman
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Nishant Garg
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States
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Walkley B, Ke X, Hussein O, Provis JL. Thermodynamic properties of sodium aluminosilicate hydrate (N-A-S-H). Dalton Trans 2021; 50:13968-13984. [PMID: 34542135 DOI: 10.1039/d1dt02202d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This study presents for the first time a systematic investigation of the thermodynamic properties of sodium aluminosilicate hydrate (N-A-S-H), through dissolution of pure synthetic N-A-S-H gels. Changes to the chemical composition and gel structure of N-A-S-H were determined via characterisation of the solid phase before and after dissolution by multinuclear solid state nuclear magnetic resonance spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, and X-ray diffraction measurements. The correlations between the bulk Si/Al ratio of the N-A-S-H phase and its thermodynamic properties were studied by characterisation of the aqueous phase and calculation of solubility constants. The solubility of synthetic N-A-S-H was compared with the solubility of metakaolin-based geopolymers with similar bulk Si/Al ratios. The solubility (log10 Ksp) of both the synthetic N-A-S-H gels and metakaolin-based geopolymers showed a close to linear correlation with the bulk Si/Al ratio of the phase. Lower solubility was observed for N-A-S-H gels and geopolymers with a higher bulk Si/Al ratio. This new insight is fundamental to understanding the physiochemical properties of geopolymers, and provides essential information for predicting their long-term stability and durability.
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Affiliation(s)
- Brant Walkley
- Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD, UK. .,Department of Chemical and Biological Engineering, The University of Sheffield, Sheffield S1 3JD, UK
| | - Xinyuan Ke
- Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD, UK. .,Department of Architecture and Civil Engineering, University of Bath, Bath BA2 7AY, UK
| | - Oday Hussein
- Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD, UK.
| | - John L Provis
- Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD, UK.
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6
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Gupta R, Tomar AS, Mishra D, Sanghi SK. Multinuclear MAS NMR Characterization of Fly‐Ash‐Based Advanced Sodium Aluminosilicate Geopolymer: Exploring Solid‐State Reactions. ChemistrySelect 2020. [DOI: 10.1002/slct.202000203] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Rainy Gupta
- Materials for radiation shielding and cement free concrete divisionCouncil of Scientific and Industrial Research- Advanced Materials and Processes Research Institute Hoshangabad road Bhopal 462064 Madhya Pradesh India
| | - Akshay Singh Tomar
- Materials for radiation shielding and cement free concrete divisionCouncil of Scientific and Industrial Research- Advanced Materials and Processes Research Institute Hoshangabad road Bhopal 462064 Madhya Pradesh India
| | - Deepti Mishra
- Materials for radiation shielding and cement free concrete divisionCouncil of Scientific and Industrial Research- Advanced Materials and Processes Research Institute Hoshangabad road Bhopal 462064 Madhya Pradesh India
| | - Sunil Kumar Sanghi
- Materials for radiation shielding and cement free concrete divisionCouncil of Scientific and Industrial Research- Advanced Materials and Processes Research Institute Hoshangabad road Bhopal 462064 Madhya Pradesh India
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7
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Sato J, Shiota K, Takaoka M. Stabilization of lead with amorphous solids synthesized from aluminosilicate gel. JOURNAL OF HAZARDOUS MATERIALS 2020; 385:121109. [PMID: 31859168 DOI: 10.1016/j.jhazmat.2019.121109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 08/26/2019] [Accepted: 08/26/2019] [Indexed: 06/10/2023]
Abstract
Lead is a hazardous heavy metal that can be stabilized by incorporation into the matrix of aluminosilicate bearing phases as they solidify. The actual mechanism by which lead is stabilized, however, continues to be unclear because the individual mechanisms of Pb incorporation into crystalline and amorphous aluminosilicate phases have not yet been studied separately. A detailed investigation of the incorporation of Pb into the amorphous phase of aluminosilicate solids was therefore performed. Amorphous aluminosilicate solids were synthesized with 0.7, 1.5, and 3.7 wt.% of Pb from aluminosilicate gel produced from chemical reagents. Based on Raman spectroscopy, the SiO stretching vibration bond shifted to lower wavenumbers with increasing Pb concentration. This shift suggested that covalent bonding between Pb and O in the matrix of the aluminosilicate solids increased. In addition, sequential extraction revealed that most of the Pb (75-90%) in the aluminosilicate solids was in a poorly soluble form (i.e., reducible, oxidizable, and residual fractions). These findings indicate that most of Pb is bonded covalently to the amorphous phase in aluminosilicate solids.
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Affiliation(s)
- Junya Sato
- Radioactive Waste Processing and Disposal Research Department, Japan Atomic Energy Agency, Muramatsu 4-33, Tokai-mura, Naka-gun, Ibaraki, 319-1194, Japan; Department of Environmental Engineering, Graduate School of Engineering, Kyoto University, Cluster C, Kyoto daigaku-Katsura, Nishikyo-ku, Kyoto, 615-8540, Japan.
| | - Kenji Shiota
- Department of Environmental Engineering, Graduate School of Engineering, Kyoto University, Cluster C, Kyoto daigaku-Katsura, Nishikyo-ku, Kyoto, 615-8540, Japan
| | - Masaki Takaoka
- Department of Environmental Engineering, Graduate School of Engineering, Kyoto University, Cluster C, Kyoto daigaku-Katsura, Nishikyo-ku, Kyoto, 615-8540, Japan
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Walkley B, Ke X, Hussein OH, Bernal SA, Provis JL. Incorporation of strontium and calcium in geopolymer gels. JOURNAL OF HAZARDOUS MATERIALS 2020; 382:121015. [PMID: 31465947 DOI: 10.1016/j.jhazmat.2019.121015] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 08/08/2019] [Accepted: 08/13/2019] [Indexed: 06/10/2023]
Abstract
Radioactive waste streams containing 90Sr, from nuclear power generation and environmental cleanup operations, are often immobilised in cements to limit radionuclide leaching. Due to poor compatibility of certain wastes with Portland cement, alternatives such as alkali aluminosilicate 'geopolymers' are being investigated. Here, we show that the disordered geopolymers ((N,K)-A-S-H gels) formed by alkali-activation of metakaolin can readily accommodate the alkaline earth cations Sr2+ and Ca2+ into their aluminosilicate framework structure. The main reaction product identified in gels cured at both 20 °C and 80 °C is a fully polymerised Al-rich (N,K)-A-S-H gel comprising Al and Si in tetrahedral coordination, with Si in Q4(4Al) and Q4(3Al) sites, and Na+ and K+ balancing the negative charge resulting from Al3+ in tetrahedral coordination. Faujasite-Na and partially Sr-substituted zeolite Na-A form within the gels cured at 80 °C. Incorporation of Sr2+ or Ca2+ displaces some Na+ and K+ from the charge-balancing sites, with a slight decrease in the Si/Al ratio of the (N,K)-A-S-H gel. Ca2+ and Sr2+ induce essentially the same structural changes in the gels. This is important for understanding the mechanism of incorporation of Sr2+ and Ca2+ in geopolymer cements, and suggests that geopolymer gels are excellent candidates for immobilisation of radioactive waste containing 90Sr.
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Affiliation(s)
- Brant Walkley
- Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD, UK
| | - Xinyuan Ke
- Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD, UK; Department of Architecture and Civil Engineering, University of Bath, Bath BA2 7AY, UK
| | - Oday H Hussein
- Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD, UK
| | - Susan A Bernal
- Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD, UK; School of Civil Engineering, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK
| | - John L Provis
- Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD, UK.
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Liu B, Zhu C, Zhuang K, Shuai L, Li D, Long W, Xing F, Fang Y. Insights into the Microstructure of Hydrothermal Synthesized Nanoscale K 2O-Al 2O 3-SiO 2-H 2O Particles. NANOMATERIALS 2019; 10:nano10010063. [PMID: 31888086 PMCID: PMC7022309 DOI: 10.3390/nano10010063] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 12/19/2019] [Accepted: 12/24/2019] [Indexed: 11/16/2022]
Abstract
K-A-S-H (K2O-Al2O3-SiO2-H2O) gel is a key phase that forms in most alkali-activated binders (eco-friendly binders which utilize a substantial amount of industrial by-product). An in-depth understanding of the microstructure and performance of this nano-sized key phase facilitates better application to alkali-activated binders. However, such studies remain little and undetailed. Therefore, our research aims to provide insights into the microstructure of K-A-S-H particles synthesized with accurate stoichiometric control by the hydrothermal method through thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and BET surface area. The results show that for materials prepared at the curing temperature lower than 80 °C, the K-A-S-H products were completely amorphous. With increased curing temperature and time, the K-A-S-H products were transformed from the amorphous phase to the crystalline zeolite phase structure, with a reduction in the specific surface area. The TG results indicate that the crystalline phase contains more non-evaporated water or zeolite water for structural rearrangement. The degree of tetrahedral polymerization slightly decreased with an increase of the K2O/SiO2 ratio as the amount of non-bridged oxygen atoms increased, whereas it gradually increased with an increase of curing temperature and time, as suggested by the FTIR and NMR results. Various K2O/SiO2 ratios resulted in the formation of zeolite K-H and K-G zeolite, both of which exhibited highly polymerized three-dimensional network structures. However, there was no significant effect of the SiO2/Al2O3 ratio on the structure of K-A-S-H products. Overall, these results provide insight into understanding the chemical stability of K-A-S-H.
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Affiliation(s)
- Bao Liu
- College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China; (B.L.); (C.Z.); (K.Z.); (L.S.); (D.L.); (W.L.); (F.X.)
- Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen 518060, China
- Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing 210009, China
| | - Chunyan Zhu
- College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China; (B.L.); (C.Z.); (K.Z.); (L.S.); (D.L.); (W.L.); (F.X.)
- Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen 518060, China
| | - Kunde Zhuang
- College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China; (B.L.); (C.Z.); (K.Z.); (L.S.); (D.L.); (W.L.); (F.X.)
- Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen 518060, China
| | - Le Shuai
- College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China; (B.L.); (C.Z.); (K.Z.); (L.S.); (D.L.); (W.L.); (F.X.)
- Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen 518060, China
| | - Dongxu Li
- College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China; (B.L.); (C.Z.); (K.Z.); (L.S.); (D.L.); (W.L.); (F.X.)
- Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen 518060, China
- Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing 210009, China
| | - Wujian Long
- College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China; (B.L.); (C.Z.); (K.Z.); (L.S.); (D.L.); (W.L.); (F.X.)
- Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen 518060, China
| | - Feng Xing
- College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China; (B.L.); (C.Z.); (K.Z.); (L.S.); (D.L.); (W.L.); (F.X.)
- Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen 518060, China
| | - Yuan Fang
- College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China; (B.L.); (C.Z.); (K.Z.); (L.S.); (D.L.); (W.L.); (F.X.)
- Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen 518060, China
- Correspondence: ; Tel./Fax: +86-755-2653-4021
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Hughes CE, Walkley B, Gardner LJ, Walling SA, Bernal SA, Iuga D, Provis JL, Harris KDM. Exploiting in-situ solid-state NMR spectroscopy to probe the early stages of hydration of calcium aluminate cement. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2019. [PMID: 30772677 DOI: 10.1016/j.mtadv.2019.100007] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We report a high-field in-situ solid-state NMR study of the hydration of CaAl2O4 (the most important hydraulic phase in calcium aluminate cement), based on time-resolved measurements of solid-state 27Al NMR spectra during the early stages of the reaction. A variant of the CLASSIC NMR methodology, involving alternate recording of direct-excitation and MQMAS 27Al NMR spectra, was used to monitor the 27Al species present in both the solid and liquid phases as a function of time. Our results provide quantitative information on the changes in the relative amounts of 27Al sites with tetrahedral coordination (the anhydrous reactant phase) and octahedral coordination (the hydrated product phases) as a function of time, and reveal significantly different kinetic and mechanistic behaviour of the hydration reaction at the different temperatures (20 °C and 60 °C) studied.
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Affiliation(s)
- Colan E Hughes
- School of Chemistry, Cardiff University, Park Place, Cardiff, Wales, CF10 3AT, UK
| | - Brant Walkley
- Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, UK
| | - Laura J Gardner
- Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, UK
| | - Samuel A Walling
- Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, UK
| | - Susan A Bernal
- Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, UK; School of Civil Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Dinu Iuga
- Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
| | - John L Provis
- Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, UK.
| | - Kenneth D M Harris
- School of Chemistry, Cardiff University, Park Place, Cardiff, Wales, CF10 3AT, UK.
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Aggregates Obtained by Alkali Activation of Fly Ash: The Effect of Granulation, Pelletization Methods and Curing Regimes. MATERIALS 2019; 12:ma12050776. [PMID: 30845744 PMCID: PMC6427724 DOI: 10.3390/ma12050776] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 02/27/2019] [Accepted: 03/01/2019] [Indexed: 11/21/2022]
Abstract
This paper presents results regarding the phase composition, microstructure and textural properties of two types of aggregates, which were prepared via crushing or pelletization of alkali-activated Class F fly ash and cured under different conditions. The alkali activator was the same for aggregate products, containing an alkaline solution consisting of 8 M NaOH and Na-silicate (8 M NaOH/Na-silicate = 1:2.5 mass ratio). The aforementioned properties were influenced by two different preparation procedures combined with varying curing regimes (under normal conditions at 20 °C, RH 40–60% for 28 and 120 days and under an accelerated regime, at 65 °C for 5 days). Aggregates were characterized using X-ray diffraction (XRD), Fourier-transform transmission infrared spectroscopy (FTIR), back scattered electron microscopy with energy dispersive spectrometer (BSE-EDS) analyses and mercury intrusion porosimetry (MIP). The results showed noteworthy structural and textural diversities between the two types of aggregate. The method of preparation and curing regime affected the formation of the N-A-S-H structure and the texture of the alkali-activated fly ash product, with the crushing method giving an advantage.
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12
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Greiser S, Gluth GJG, Sturm P, Jäger C. 29Si{ 27Al}, 27Al{ 29Si} and 27Al{ 1H} double-resonance NMR spectroscopy study of cementitious sodium aluminosilicate gels (geopolymers) and gel-zeolite composites. RSC Adv 2018; 8:40164-40171. [PMID: 35558254 PMCID: PMC9091287 DOI: 10.1039/c8ra09246j] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Accepted: 11/27/2018] [Indexed: 11/23/2022] Open
Abstract
The influence of starting materials and synthesis route on the properties and the structure of cementitious sodium aluminosilicate gels is not fully understood, partly due their amorphous nature and the fact that they often contain residual reactants, which can make the results of single-pulse NMR spectroscopy applied to these materials difficult to interpret or ambiguous. To overcome some of these limitations, 29Si{27Al} TRAPDOR NMR as well as 27Al{29Si} and 27Al{1H} REDOR NMR spectroscopy were applied to materials synthesized by the one-part alkali-activation route from three different amorphous silica starting materials, including rice husk ash. The latter led to formation of a fully amorphous sodium aluminosilicate gel (geopolymer), while the materials produced from the other silicas contained amorphous phase and crystalline zeolites. Application of the double-resonance NMR methods allowed to identify hydrous alumina gel domains in the rice husk ash-based material as well as significantly differing amounts of residual silica in the three cured materials. Four-coordinated Al existed not only in the aluminosilicate gel framework but also in a water-rich chemical environment with only a small amount of Si in proximity, likely in the alumina gel or possibly present as extra-framework Al in the aluminosilicate gel. The results demonstrate how the employment of different silica starting materials determines the phase assemblage of one-part alkali-activated materials, which in turn influences their engineering properties such as the resistance against chemically/biologically aggressive media.
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Affiliation(s)
- Sebastian Greiser
- Division 1.3 Structure Analysis, Bundesanstalt für Materialforschung und -prüfung (BAM) Richard-Willstätter-Str. 11 12489 Berlin Germany
| | - Gregor J G Gluth
- Division 7.4 Technology of Construction Materials, Bundesanstalt für Materialforschung und -prüfung (BAM) Unter den Eichen 87 12205 Berlin Germany
| | - Patrick Sturm
- Division 7.4 Technology of Construction Materials, Bundesanstalt für Materialforschung und -prüfung (BAM) Unter den Eichen 87 12205 Berlin Germany
| | - Christian Jäger
- Division 1.3 Structure Analysis, Bundesanstalt für Materialforschung und -prüfung (BAM) Richard-Willstätter-Str. 11 12489 Berlin Germany
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13
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14
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Synthesis of Nanoscale CaO-Al₂O₃-SiO₂-H₂O and Na₂O-Al₂O₃-SiO₂-H₂O Using the Hydrothermal Method and Their Characterization. MATERIALS 2017; 10:ma10070695. [PMID: 28773061 PMCID: PMC5551738 DOI: 10.3390/ma10070695] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Revised: 06/11/2017] [Accepted: 06/12/2017] [Indexed: 11/17/2022]
Abstract
C-A-S-H (CaO-Al₂O₃-SiO₂-H₂O) and N-A-S-H (Na₂O-Al₂O₃-SiO₂-H₂O) have a wide range of chemical compositions and structures and are difficult to separate from alkali-activated materials. Therefore, it is difficult to analyze their microscopic properties directly. This paper reports research on the synthesis of C-A-S-H and N-A-S-H particles with an average particle size smaller than 300 nm by applying the hydrothermal method. The composition and microstructure of the products with different CaO(Na₂O)/SiO₂ ratios and curing conditions were characterized using XRD, the RIR method, FTIR, SEM, TEM, and laser particle size analysis. The results showed that the C-A-S-H system products with a low CaO/SiO₂ ratio were mainly amorphous C-A-S-H gels. With an increase in the CaO/SiO₂ ratio, an excess of Ca(OH)₂ was observed at room temperature, while in a high-temperature reaction system, katoite, C₄AcH11, and other crystallized products were observed. The katoite content was related to the curing temperature and the content of Ca(OH)₂ and it tended to form at a high-temperature and high-calcium environment, and an increase in the temperature renders the C-A-S-H gels more compact. The main products of the N-A-S-H system at room temperature were amorphous N-A-S-H gels and a small amount of sodalite. An increase in the curing temperature promoted the formation of the crystalline products faujasite and zeolite-P. The crystallization products consisted of only zeolite-P in the high-temperature N-A-S-H system and its content were stable above 70%. An increase in the Na₂O/SiO₂ ratio resulted in more non-bridging oxygen and the TO₄ was more isolated in the N-A-S-H structure. The composition and microstructure of the C-A-S-H and N-A-S-H system products synthesized by the hydrothermal method were closely related to the ratio of the raw materials and the curing conditions. The results of this study increase our understanding of the hydration products of alkali-activated materials.
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