Hybrid binders based on blends of Portland cement and alkali-activated aluminosilicates have been the object of intense study in recent years as a promising alternative to ordinary Portland cement (OPC).The unusually high alkalinity of these hybrid cements necessitates a thorough understanding of the effect of a high concentration of alkalis on the mineralogical phases comprising such hybrid systems.The present study explored the behaviour of laboratory-synthesized dicalcium silicate (C2S) in alkaline media.C2S was hydrated in three liquid media:water, 8-M NaOH and 4 wt % Na2CO3.Hydration kinetics was studied via isothermal conduction calorimetry and 2-and 28 day mechanical strength development was determined.The reaction products were characterised with XKD a(x)Si NMR.The findings showed that hydration kinetics was faster in C2S hydrated in the presence of alkalis than in the reference material (C2S + water).Compressive strength was also higher in the former.