In each of the three samples hydrated in the presence of sodium sulfate, chloride, or nitrate, we detect only one distinctive hydrate phase after three hours (Figure ). Specifically, the sodium nitrate sample exhibits a reflection at 8.4 • with a basal d -spacing of 10.5 Å (green circle). The values determined are in agreement with those described by Balonis et al. for nitrate AFm in wet conditions (≈ 100 % RH) . Therefore, the formation of nitrate AFm was observed exclusively in the sodium nitrate-containing sample. The reflection at 11.0 • in the sample hydrated in the sodium chloride solution can be related to the chloride containing AFm phase, Friedel's salt (orange square) . Furthermore, ettringite (blue star)