Alkaline Hydration Of C sub(2)S and C sub(3)S

This study analyzed the behavior of two laboratory-synthesized calcium silicates, C sub(3)S and C sub(2)S, after hydration in 8-M NaOH and in water as a control. Two- and 28-d mechanical strength values were determined and the products were characterized with XRD, TEM, and super(29)Si and super(23)Na MAS NMR. The results showed that hydrating C sub(3)S in a highly alkaline medium had no significant effect on the mechanical development of the material, whereas in C sub(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.