Hydration of ferrite Ca2AlFeO5 in the presence of sulphates and bases

The reaction of synthetic Ca2AlFeO5 at 20 degrees C with (a) H2O; (b) H2O, CaSO4 . 2H(2)O; (c) H2O, CaSO4 . 1/2H(2)O; (d) H2O, CaSO4 . 2H(2)O, Na2SO4; (e) H2O, CaS04 . 2H(2)O, K2SO4; (f) H2O, CaSO4 . 2H(2)O, Ca(OH)(2); (g) H2O, CaSO4 . 2H(2)O, Ca3SiO5; (h) H2O, CaSO4 . 2H(2)O, KOH; was studied by differential scanning calorimetry and X-ray powder diffraction. Acetone dried samples were examined at hydration times between 2 min and 28 days, and 4 months in the instance of experiments (f) and (g). In (a) AFm forms immediately followed by hydrogarnet, while in (b-e) the formation of AFm is delayed, since the initial product is AFt, which then transforms into AFm. In the more basic samples (f-g), AFm formation is further delayed due to the introduction of a pronounced dormant period during AFt formation. The strongly basic sample (h) also exhibits this dormant period, but less AFt is formed and AFm appears as in (b-e). Copyright (C) 1996 Elsevier Science Ltd