Mechanosynthesis of tricalcium aluminum hydrate[3CaOAl(2)O(3)6H(2)O] was attempted at room temperature by mixed grinding of constituent materials. The materials used were calcium oxide [CaO], calcium hydroxide [Ca(OH)(2)], kaolinite [Al4Si4O10(OH)(8)] and gibbsite [Al(OH)(3)]. The CaO or Ca(OH)(2) sample was mixed to kaolinite or gibbsite by 2:1 in weight ratio. These mixtures were subjected to grinding for various times under dry atmospheric condition in a planetary ball mill. The dry grinding on the mixture of kaolinite and Ca(OH)(2) enables us to produce 3CaOAl(2)O(3)6H(2)O by one hour of grinding, despite the free energy change of the reaction system is positive from room temperature to 373 K, suggesting no spontaneous reaction takes place. No formation of 3CaOAl(2)O(3)6H(2)O is brought about by the grinding of the CaO-kaolinite system within the scope of this experiment. The mechanosynthesis between Ca(OH)(2) and Al(OH)(3) occurs within 30 minutes, which is much shorter than that for the Ca(OH)(2)-kaolinite system, because of lower positive free energy change than that for the Ca(OH)(2)-kaolinite system. Tricalcium aluminum hydrate obtained in this work is changed to anhydrate form (3CaOAl(2)O(3)) at around 800 K, which is much lower by about 923 K than that in the current production process of Portland cement. The ground products containing 3CaOAl(2)O(3)6H(2)O shows the hardening property by adding water. Hardness of the body increases with increase in grinding time, however, prolonged grinding does not contribute further increase in the hardness.
