Up to 0.5 wt.% Zn also had no effect on the hydration of
C3A. But with higher concentrations of 2.5 and 5.0 wt.%
Zn, the hydration was slightly retarded and the content of
hexagonal hydrates increased. In these samples the compound
Ca(Zn(OH)3)2 · 2H2O could be found. Lieber [8] identified
this compound during the early hydration of cement, when
the cement paste was retarded by Zn. Tashiro and Oba [5]
found in their work that the hydration of C3A with 7.0 wt.%
of ZnO (just mixed with C3A and not burned) was retarded,
and less C3AH6 and more hexagonal hydrates formed. They
did not report any other hydration product containing Zn.