Abstract: The structure of calcium aluminate powder will be strongly affected by the changes of raw materials.The structure and dissolution rate of calcium aluminates，which were produced with activator and without activator，were identified and measured.XRD and TGA analysis showed that after adding activator，the mineral phase of calcium aluminate powder contained halide，in which the mineral phase CaAl₃XO₇ may be partially hydrolyzed to form Friedel′s salt double hydroxide phases.Furthermore，this calcium aluminate powder had two IR spectral feature peaks at 2 116 cm^-1 and 1 981 cm^-1.Different mineral phases，dissolution rates of Al₂O₃ in the calcium aluminate powder were quite different.

Key words: calcium aluminate powder, mid-FT-IR, structure identification, dissolution rate