Chloride ion binding capacity of aluminoferrites

The hydration of aluminoferrites (C4AF, C6AF2 and C6A2F) and their mixture with gypsum (up to 10/5 ratio) was investigated as well as their chloride binding capacity (after immersion in 10% NaCl solution) by thermal tests (DTG and TGA) and X-ray diffraction (XRD). Hydration products of these aluminoferrites are similar to that of C3A, but amorphous AH3 and/or FH3 are formed, and transformation of metastable (hexagonal hydrates) to the stable (hydrogarnet) phase is slower. Iron content of aluminoferrites determines the rate of hydration reactions: hydration rate increases in the order C6A2F>C4AF>C6AF2. In the case of C4AF+gypsum mixtures, monosulfate was found prior to the total exhaustion of gypsum. After salt treatment, iron-containing Friedel's salt or Kuzel's salt was found. Characteristics of DTG peaks are described and interpreted.