Crystal structure refinement and hydration behaviour of doped tricalcium aluminate

In this paper analytical evidence on crystal structure and hydration behaviour of C3A solid solutions with MgO, SiO2, Fe2O3, Na2O and K2O is given. Samples were prepared using an innovative sol-gel process as precursor, examined by X-ray powder diffraction, infra-red spectroscopy and the crystal structure was refined by the Rietveld method. A significant shift of lattice parameters was found for C3A solid solutions with SiO2, Fe2O3 or Na2O but only minor changes were detected for K2O. The hydration of C3A solid solutions in the absence of CaSO4 was accelerated for samples doped with SiO2 or K2O and it was retarded in the case of MgO, Fe2O3 or Na2O. The hydration in the presence of CaSO4 was accelerated when C3A was doped with K2O or Na2O, whereas Fe2O3 strongly retarded the hydration. The doping with SiO2 nearly had no influence on the hydration, the effect of MgO was not straight forward.