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The evolution of interfacial transition zone in alkali-activated fly ash-slag concrete

Fang, G; Zhang, M; (2020) The evolution of interfacial transition zone in alkali-activated fly ash-slag concrete. Cement and Concrete Research , 129 , Article 105963. 10.1016/j.cemconres.2019.105963. Green open access

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Abstract

This paper investigates the mechanisms of microstructure evolution of interfacial transition zone (ITZ) in alkali-activated fly ash-slag (AAFS) concrete using scanning electron microscope. Results indicate that the formation of original ITZ depends on the so-called “wall effect”, leading to a deficit of large grains and a higher effective alkaline activator/precursor ratio compared to paste matrix. The alkaline reaction process is correspondingly accelerated, which promotes the formation of low Ca C-(N)-A-S-H gels and reduces the porosity in the ITZ. Afterwards, the high Ca C-(N)-A-S-H gels are generated due to the release of more Ca from slag, resulting in the continuous refinement of pores. The C-(N)-A-S-H gels with rich Si and Al are then produced at 7 d, attributing to the species diffusion from paste matrix to ITZ. Consequently, a compact and dense microstructure is formed in the ITZ at 28 d, which would be beneficial to the long-term performance of concrete.

Type: Article
Title: The evolution of interfacial transition zone in alkali-activated fly ash-slag concrete
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.cemconres.2019.105963
Publisher version: https://doi.org/10.1016/j.cemconres.2019.105963
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Alkali-activated materials (D), Microstructure (B), Pore size distribution (B), Backscattered electron imaging (B), X-ray mapping (B)
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Civil, Environ and Geomatic Eng
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/10089440
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