X-ray microtomography shows pore structure and tortuosity in alkali-activated binders

John L. Provis, Rupert J. Myers, Claire E. White, Volker Rose, Jannie S. J. van Deventer

Research output: Contribution to journalArticlepeer-review

Abstract

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.
Original languageEnglish
Pages (from-to)855-864
JournalCement and Concrete Research
Volume42
Issue number6
DOIs
Publication statusPublished - 2012

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