György Balázs

Chloride ion binding capacity of aluminoferrites

Abstract The hydration of aluminoferrites (C 4 AF, C 6 AF 2 and C 6 A 2 F) 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 C 3 A, but amorphous AH 3 and/or FH 3 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 C 6 A 2 F>C 4 AF>C 6 AF 2 . In the case of C 4 AF+gypsum mixtures, monosulfate was found prior to the total exhaustion of gypsum. After salt treatment, iron-containing Friedels salt or Kuzels salt was found. Characteristics of DTG peaks are described and interpreted.