We used in-situ calorimetry and XRD to characterize the hydration of a C 3 A model suspension containing different amounts of alkali salt. The intensity of the early C 3 A hydration was attenuated in the order Na 2 SO 4 > NaCl ≈ NaNO 3 . However, the initial C 3 A hydration was not fully inhibited by any of the evaluated salt concentrations. The XRD analysis confirmed ettringite formation, Friedel's salt, and mononitrate in the presence of the corresponding alkali salts. However, we could not detect AH 3 or AFm phases like monosulfate and C 4 AH 19 that are predicted to form based on thermodynamic modeling.