Dyckerhoff cement was substituted by 15 mass% of silica fume (SF), metakaolin (MK), ground granulated blast- furnace slag (BFS) or their combination. Phase changes and their impact on porous structure and compressive strength were investigated from 7 up to 28 days of hydrothermal curing at 165 degrees C and 0.6 MPa. Since the amount of jaffeite did not change significantly with prolongation of autoclaving time, ongoing coarsening of structure resulting in substantial increase of permeability coefficient and decrease of compressive strength depended mainly on the increasing quantity of alpha-C2SH. The most significant negative changes were demonstrated in referential samples as well as samples containing BFS. Any of the undesired phases were evidenced in the composition prepared with SF. Particular samples showed character of structure and compressive strength comparable or even better than corresponding samples cured under standard conditions.