Journal
CEMENT AND CONCRETE RESEARCH
Volume 129, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.cemconres.2019.105963
Keywords
Alkali-activated materials; Microstructure; Pore size distribution; Backscattered electron imaging; X-ray mapping
Funding
- Engineering and Physical Sciences Research Council (EPSRC), UK [EP/R041504/1, EP/N509577/1]
- Royal Society, UK [IE150587]
- China Scholarship Council (CSC)
- University College London (UCL)
- EPSRC [EP/R041504/1] Funding Source: UKRI
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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.
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