HYDRATION PRODUCTS OF CALCIUM ALUMINOFERRITE IN THE PRESENCE OF GYPSUM

Hydration products of C6A2F, C4AF and C6AF2 in the presence of gypsum were studied by DTA, XRD, EDAX and IR techniques. An iron-rich phase, containing little calcium, was found in their hydrates. DTA proved to be an effective method to detect this phase if it was enriched. Good linear relationships were obtained between optical densities and Fe/(Fe+Al) ratios in AFm phases when infrared absorption bands between 1200-960 cm-1 were fitted by Gaussian-line-shape curves. The correlations suggested that the intensity of the absorption of nu3-SO42- could quantify the amount of Fe(III) in AFm phases. A possible explanation of this result was tentatively proposed as well.