Hydration behavior of iron doped calcium sulfoaluminate phase at room temperature

Different samples of calcium sulfoaluminate phase doped with iron, (Ca4Al(6-2x)Fe2xSO16) with x = 0, 0.2 and 0.5, were synthesized at 1350°C. The hydration kinetics of the resulted phases was investigated by calorimetric and conductimetric techniques. The hydrated samples were analyzed by X-ray diffraction and scanning electron microscopy. The hydration of calcium sulfoaluminate was slightly modified by inclusion of iron in its structure. Dissolution rate of calcium sulfoaluminate phase doped with iron appeared to be slowed down such as the nucleation rate during the induction period while the percentage of reaction after 1 day was slightly increased. The analysis of hydrates indicated the formation of the same hydrates, ettringite and calcium monosulfoaluminate and the gibbsite, with or without iron replacement. Gibbsite played a major role in the kinetics of the induction period and thus the presence of iron may decrease its nucleation rate forming (A, F)H3 instead of AH3.