Abstract
This contribution analyzes the structure of sodium-lime-silica (SLS) glass alkali-activated with NaOH. The mix forms an alkali-activated cement (AAC), which has proven to be mechanically resistant when immerged under water. The aim is to determine whether the presence of calcium in the glass powder may have contributed, together with alkali-activation, to forming calcium silicate hydrates (C-S-H), which are responsible for water resistance in hydrated Portland cement pastes. This is investigated by SEM, where needles similar to C-S-H in Portland paste are observed, then by X Ray Diffraction (XRD), but the pastes are too amorphous to allow any phase identification. Finally, 29Si magic angle spinning nuclear magnetic resonance (MAS NMR) shows that C-S-H are at most 2–3% in the 4 M and 8 M NaOH AAC pastes, so that they cannot be considered responsible for the water resistance of SLS glass AAC pastes and mortars. The latter are rather formed of sodium silicate hydrates and/or silica gel.
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