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

John L. Provis, Rupert J. Myers, Claire Emily White, Volker Rose, Jannie S.J. Van Deventer

Research output: Contribution to journalArticlepeer-review

409 Scopus citations


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 (US)
Pages (from-to)855-864
Number of pages10
JournalCement and Concrete Research
Issue number6
StatePublished - Jun 2012

All Science Journal Classification (ASJC) codes

  • Building and Construction
  • General Materials Science


  • Alkali activated cement (D)
  • Microstructure (B)
  • Transport properties (C)
  • X-ray microtomography


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