is the only hydrate phase precipitating after 3 h of hydration in the sodium sulfate solution, also observed, for example, by Liu et al. as hydration product of pure cubic C 3 A in the presence of Na 2 SO 4 (w/s = 1) . Electron microscope images of the precipitated hydrate phases for all systems are provided in the Supporting Information (Figures and). The characteristic reflection of the U-phase (at approx.