Alkaline Hydration Of C ₂ S and C ₃ S

This study analyzed the behavior of two laboratory‐synthesized calcium silicates, C 3 S and C 2 S, after hydration in 8‐ M Na OH and in water as a control. Two‐ and 28‐d mechanical strength values were determined and the products were characterized with XRD , TEM , and 29 Si and 23 Na MAS NMR . The results showed that hydrating C 3 S in a highly alkaline medium had no significant effect on the mechanical development of the material, whereas in C 2 S hydration, that medium hastened hydration substantially, impacting setting and hardening times. This finding has technological implications, given the low early‐age reactivity of dicalcium silicate under normal hydration conditions.