CHLORIDE ION BINDING CAPACITY OF TETRACALCIUM ALUMINOFERRITE

Abstract

The hydration of aluminoferrites 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. In this first part, C₄AF has been investigated, to be followed by C₆AF₂ and C₆A₂F in the second part. Hydration products of C₄AF are similar to that of C₃A, but amorphous AH₃ and/or FH₃ are formed, and the transformation of metastable (hexagonal hydrates) to the stable (hydrogarnet) phase is slower. In 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.