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

This paper deals with the design, synthesis, hydration mechanism and hydration products of novel Ba 2+ -, Cu 2+ - or Bi 3+ -doped CaO–Al 2 O 3 –ZrO 2 -based cementitious materials used for heavyweight concrete mixes. The results of the heating microscopy thermal analysis indicated that both Cu and Bi in a Ca 7 ZrAl 6 O 18 -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 Ba 2+ -doped Ca 7 ZrAl 6 O 18 along with accessory (Ca,Ba)ZrO 3 with a perovskite‐type structure and BaAl 2 O 4 phases having high melting points were formed. The presence of metal ions, i.e., Cu 2+ or Bi 3+ , 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 Ba 2+ doping ions, this effect was the least noticeable. The effect of metal ions including Ba 2+ , Cu 2+ and Bi 3+ on microstructural features of cement pastes was investigated by SEM–EDS. These doping ions strongly affected the morphologies of Ca–Al hydrates.