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Hos, James P; McCormick, Patrick G.; Byrne, Lindsay T.

doi:10.1023/a:1015329619089

Cited by 73 publications

(28 citation statements)

References 8 publications

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“…The appearance of the level 1 poresolid structure in some regions is vaguely similar to that of agglomerations of spheres coalesced to different degrees. This structure is similar to that in other metakaolin (Bell et al, 2006;Kriven et al, 2003) and synthetic (Hos et al, 2002) geopolymers. The appearance and size of this structure varies significantly with processing variables and throughout a single specimen: Fig.…”

Section: Ultra-small-angle Neutron Scatteringsupporting

confidence: 82%

“…Subsequently, similar synthesis conditions have been used with other reactive aluminosilicates [e.g. fly ash (Palomo et al, 1999) and synthetic melt quenched aluminosilicates (Hos et al, 2002)] to make products also referred to as geopolymers. Alternative names used in the literature for describing geopolymers include 'low-temperature aluminosilicate glass', 'alkali-activated cement', 'geocement', 'hydroceramic', 'alkali-bonded ceramic', 'aluminosilicate inorganic polymer' (AIP) and 'low-temperature inorganic polymer glass' (LTIPG or IPG) (Rahier et al, 1995;Rowles, 2004;Duxson, Fernandez-Jimenez et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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Characterization of the pore structure of metakaolin-derived geopolymers by neutron scattering and electron microscopy

et al. 2011

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The pore–solid structure of selected high-compressive-strength metakaolin geopolymers has been characterized to facilitate quantitative prediction of their physical properties. Geopolymers are multiphase materials with pore widths ranging from subnanometre to several tenths of a millimetre. Ultramicrotoming of resin-embedded grains was found to be an effective method for producing electron-transparent sections. Scanning and transmission electron microscopy showed the existence of a bi-level pore system and heterogeneity of the pore morphology. Ultra-small-angle neutron scattering, of sufficiently thin specimens, was found to be useful in detecting the length scales on which statistically significant structural changes occur as the geopolymer chemical composition is varied. Contrast variation experiments confirmed that the small-angle neutron scattering from an Si:Al:Na = 2.5:1:1.2 geopolymer before and after dehydration was dominated by scattering from pores. These experiments suggested the presence of closed (under current experimental conditions) pores in the dehydrated geopolymer. A three-phase analysis was developed for this system, and the scattering of the solid, open pore and closed pore phases was determined as a function of scattering length density ρ. The scattering from all three phases had the sameqdependence over the range of likely ρ within the uncertainties. A lower limit of 4.21 (6) × 1010 cm−2was determined for the scattering length density ρwof the nondehydrated geopolymer by assuming the pore fluid to be water. This scattering length density is significantly higher than the expected value of approximately 3.4 × 1010 cm−2. Small-angle neutron scattering from the dehydrated and nondehydrated Si:Al:Na = 2.5:1:1.2 geopolymer showed that dehydration does not cause a severe change in morphology of the nanoporosity on the length scale probed.

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Section: Ultra-small-angle Neutron Scatteringsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Characterization of the pore structure of metakaolin-derived geopolymers by neutron scattering and electron microscopy

et al. 2011

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“…The better development of early-age strength of geopolymer at 1 day was obtained in sample using small ratio of H2O/Na2O. This suggested that the higher H2O content, the lower concentration of alkaline activator leading to the difficulty of silica and alumina breakdown from raw material resulting in insufficient SiO4 and AlO4 tetrahedral units to form geopolymeric gel [13]. In addition, the system that had higher H2O/Na2O, for example, at H2O/Na2O of 20 (NH166) favoured the formation of various zeolite products.…”

Section: Mechanical Property and Characterizations Of Geopolymer Samplesmentioning

confidence: 88%

Variable Factors Controlling Amorphous-Zeolite Phase Transformation in Metakaolin Based Geopolymer

Juengsuwattananon¹,

Pimraksa²

2017

Acta Metall Slovaca

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Metakaolin based geopolymer binder was synthesized using variable factors such as Na2O/SiO2, Na2O/Al2O3 and H2O/Na2O molar ratios as well as curing time. Metakaolin was used as an alumino-silicate source incorporating with strong alkali activators; sodium hydroxide solution to undergo polycondenation and hence a formation of hardened geopolymeric binder. This work was aimed to investigate the effect of Na2O/SiO2, Na2O/Al2O3 and H2O/Na2O ratios, as well as curing time on phase transformation. The chemical composition, phase development and microstructure of reaction products were examined by X-ray fluorescence, X-ray diffraction analysis and scanning electron microscopy with respect to their final compressive strength. Increasing the molar ratios of Na2O/Al2O3 and H2O/Na2O tended to favour the transformation of amorphous gel to various types of crystalline zeolite. Sodalite (pseudo-phase zeolite) and zeolite belonging to the Faujasite group, as well as zeolite X and A were identified in these mixtures. Based on this study, systems that favoured the formation of zeolitic products tended to possess lower strengths.Keywords: Geopolymer binder, Microstructure, Zeolite, Amorphous gel, Aluminosilicates IntroductionGeopolymer or alkali polysialate is an entirely known material that could be used in a wide range of potential applications includes: fire resistant materials, thermal insulation, ceramic tiles, thermal shock refractories, cements and concretes, high-tech composites aircraft interior and automobile, radioactive and toxic waste containment, arts and decoration. These can be formed by mixing aluminate and-silicate materials such as silica fume, fly ash, rice husk ash, slag, waste glass, industrial wastes, kaolinite and metakaolin with strong alkali activators or solution [1][2][3]. The basic of geopolymerization process involve dissolution of solid alumino-silicate oxides in alkali hydroxide or alkali silicate solution, diffusion or transportation of the dissolved Si and Al complexes from the initial raw material, formation of a gel phase and finally hardening of the gel phase. The hydration products forming in the thee-dimensional rigid network geopolymer are composed of variety structures, such as amorphous phase, semi-crystalline phase, as well as fully crystalline zeolite phase. A high content of amorphous geopolymeric gel resulted to the high compressive strength, while a formation of zeolite phase in geopolymer matrix produced lower strength [4][5][6][7].

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“…However, the chemical composition of these materials is very complicated and a fundamental investigation into the mechanism of geopolymerization has proven to be difficult. Although Metakaolin is usually used in the study of geopolymerization mechanisms because of its simple chemical composition compared to the other common precursor materials, impurities in the Metakaolin complicate the study of the geopolymerization process [3][4][5][6]. Usually, Metakaolin is fabricated through calcination of Kaolin (Al 2 O 3 Á2SiO 2 Á2H 2 O) at 600-900°C [7,8], however, the Metakaolin is not pure and the atomic ratio of Al/Si is not consistent due to the fact that the age and location of the Kaolin mines are different.…”

Section: Introductionmentioning

confidence: 99%