Investigating the origins of metakaolin surface reactivity in the context of alkali-activated binders

Author(s): V. Benavent (1), Q. H. Nguyen (1), J.-B. d’Espinose de Lacaillerie (1), M. Ma-rinova-Atanassova (2), A.-M. Blanchenet (3) and C. A. Davy
Paper category: Proceedings
Book title: Proceedings of the International Conference on Sustainable Materials, Systems and Structures (SMSS2019) New Generation of Construction Materials
Editor(s): Marijana Serdar, Nina Štirmer, John Provis
ISBN: 978-2-35158-217-6,
Vol 1. ISBN: 978-2-35158-223-7
e-ISBN: 978-2-35158-218-3
Publisher: RILEM Publications SARL
Publication year: 2019
Pages: 51-58
Total Pages: 8
Language : English

Abstract: This contribution represents our current attempt to understand the origin of metakaolin reactivity in the context of alkali-activated binders (geopolymers). To this purpose, a pure non-calcined kaolinite and two commercial metakaolinites (MK1 and MK2), are compared by using a combination of techniques. First, we investigate the potential of solid state Dynamic Nuclear Polarization (DNP) enhanced Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) in order to reveal the specific sites of MK surface. This technique yields drastic improvements in NMR signal intensity from oxide surfaces, allowing to determine the surface coordination of aluminum and silicon on the MK surfaces under consideration. For Si, no significant difference between the bulk and surface responses is found for both MK. For Al, differences were found. Secondly, nitrogen sorption isotherms and Transmission Electron Microscopy (TEM) were coupled to investigate the pore structure, the texture and morphology of kaolinite and MK, in relation to their reactivity. Total adsorbed nitrogen volume is significantly greater for MK1 than MK2 (and than kaolinite). With careful 2D Scanning TEM (STEM) imaging, it is shown that depending on calcination, the typical platelet morphology of kaolinite can be retained, but this is not directly related to reactivity.

Online publication : 2019
Publication type : full_text
Public price (Euros) : 0.00