Synthesis, characterization and hydration analysis of Ba2+-, Cu2+- or Bi3+-doped CaO–Al2O3–ZrO2-based cements

Abstract

This paper deals with the design, synthesis, hydration mechanism and hydration products of novel Ba2+-, Cu2+- or Bi3+- doped CaO–Al2O3–ZrO2-based cementitious materials used for heavyweight concrete mixes. The results of the heating microscopy thermal analysis indicated that both Cu and Bi in a Ca7ZrAl6O18-based cement clinker can effectively reduce the sintering temperature by 150–200 C. Incorporation of barium for the synthesis of calcium zirconium aluminate-based hydraulic binder increased its thermal resistance since Ba2+-doped Ca7ZrAl6O18 along with accessory (Ca,Ba)ZrO3 with a perovskite-type structure and BaAl2O4 phases having high melting points were formed. The presence of metal ions, i.e., Cu2+ or Bi3+, created conditions which were favorable for the formation of hexagonal calcium aluminate hydrates rather than the cubic one, as confirmed by coupled DSC–TG/EGA–MS thermal analysis techniques and X-ray diffraction. For the Ba2+ doping ions, this effect was the least noticeable. The effect of metal ions including Ba2+, Cu2+ and Bi3+ on microstructural features of cement pastes was investigated by SEM–EDS. These doping ions strongly affected the morphologies of Ca–Al hydrates.