Mechanochemical activation by intensive milling has been studied in this paper as a way to produce amorphous kaolin with pozzolanic activity. Physical-chemical properties, pozzolanic reactivity and the effect they have on cement hydration were evaluated for two types of the mechanically activated kaolin in comparison with a reference cement paste. At 10% replacement level, using of the mechanically activated kaolins acted in favor of the pozzolanic reaction in the blended cement paste. The pozzolanic reaction of this kind of kaolin significantly reduced the portlandite content (calcium hydroxide) in different ages of the blended cement. The combined effect of hydration and better pozzolanic reaction of the cement containing mechanochemical kaolins has been revealed in improvement of the mechanical properties of the mortars at the early times.
