Ceramics-Silikáty 52, (3) 183 - 189 (2008)

The finest cement fraction is collected in the sleeve filters during cement clinker milling. It is estimated that after the first 24 hours of hydration the finest cement fraction is characterized by a high initial compressive strength. Moreover, in this fraction, the ettringite that is formed during the hydration due to high gypsum content reduces the strength of samples. The addition of natural pozzolana (tripoli) ensures a stable structure of cement stone. The amount of portlandite significantly decreases or completely disappears; also most of ettringite decomposes during the hardening of samples containing tripoli. After one day of hardening, the compressive strength of the finest cement fraction samples containing tripoli increases to 15-20 MPa. After 28 days of hardening, the compressive strength reached over 32.5 MPa. The finest cement fraction containing tripoli additive may be used as a separate product of cement manufacturing, distinguished by early hardening.