Formation and hydraulic behavior of chromium-phosphorus doped calcium sulfoaluminate cement

The formation and the hydration processes of solid solutions based on calcium sulfoaluminate with chromium and phosphorus additions are studied. The synthesized solid solutions are analyzed with X-ray diffraction and infrared spectroscopy. The high concentrations of additives slow the formation of the calcium sulfoaluminate phase. The early hydration behavior is followed by Tian-Calvet calorimetry. The results show that incorporation of chromium and phosphorus in the crystal lattice of calcium sulfoaluminate induces a long induction period. The setting period in the doped sample has a higher heat output than the pure phase. Identification of the hydration products is done by differential thermal analysis (DTA). The degree of transformation of ettringite into the monosulfate is lower in the modified calcium sulfoaluminate than in the additives-free cement.