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X-ray microtomography shows pore structure and tortuosity in alkali-activated binders
Durability of alkali-activated binders is of vital importance in their commercial application, and depends strongly on microstructure and pore network characteristics. X-ray microtomography (µCT) offers, for the first time, direct insight into microstructural and pore structure characteristics in three dimensions. Here, µCT is performed on a set of sodium metasilicate-activated fly ash/slag blends, using a synchrotron beamline instrument. Segmentation of the samples into pore and solid regions is then conducted, and pore tortuosity is calculated by a random walker method. Segmented porosity and diffusion tortuosity are correlated, and vary as a function of slag content (slag addition reduces porosity and increases tortuosity), and sample age (extended curing gives lower porosity and higher tortuosity). This is particularly notable for samples with ≥ 50% slag content, where a space-filling calcium (alumino)silicate hydrate gel provides porosity reductions which are not observed for the sodium aluminosilicate ('geopolymer') gels which do not chemically bind water of hydration.
X-ray microtomography shows pore structure and tortuosity in alkali-activated binders
Durability of alkali-activated binders is of vital importance in their commercial application, and depends strongly on microstructure and pore network characteristics. X-ray microtomography (µCT) offers, for the first time, direct insight into microstructural and pore structure characteristics in three dimensions. Here, µCT is performed on a set of sodium metasilicate-activated fly ash/slag blends, using a synchrotron beamline instrument. Segmentation of the samples into pore and solid regions is then conducted, and pore tortuosity is calculated by a random walker method. Segmented porosity and diffusion tortuosity are correlated, and vary as a function of slag content (slag addition reduces porosity and increases tortuosity), and sample age (extended curing gives lower porosity and higher tortuosity). This is particularly notable for samples with ≥ 50% slag content, where a space-filling calcium (alumino)silicate hydrate gel provides porosity reductions which are not observed for the sodium aluminosilicate ('geopolymer') gels which do not chemically bind water of hydration.
X-ray microtomography shows pore structure and tortuosity in alkali-activated binders
Provis, John L. (author) / Myers, Rupert J. (author) / White, Claire E. (author) / Rose, Volker (author) / Van Deventer, Jannie S.J. (author)
Cement and Concrete Research ; 42 ; 855-864
2012
10 Seiten
Article (Journal)
English
Gel , X-Strahl , Natrium , Flugasche , Calcium , Silicate , Hydrat , Natriumsilicat , Geopolymer , Diffusion , Hydratation , Porenstruktur , Mikrostruktur , Porosität
X-ray microtomography shows pore structure and tortuosity in alkali-activated binders
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