Long-term hydration of CaSiO⁴ with combined additions of silica fume, calcium sulpha aluminate and gypsum

Slow hydration of γ-C₂S in mixtures of β and γ polymorphs was observed between 17 and 40 months of curing, but did not occur in the presence of silica fume. The detection of cross-linked silicate species by nuclear magnetic resonance (Q³) is attributed to the formation of silica gel because of the low effective CIS molar ratio in mixtures containing silica fume. The formation of ettringite from additons of C₄A₃S and gypsum prevents the hydration of β-C₂S unless free lime is also present in the mixture.