Ceramics-Silikáty 64, (3) 338 - 347 (2020)

Calcium barium sulfoaluminate (abbr. C_4-xB_xA₃$), one of the special cementitious minerals originated from ye'elimite (abbr.C₄A₃$), has superior hydration and hardening performance. In this paper, a series of C_4-xB_xA₃$ with different Ba-doping concentrations (x=0, 0.5, 1, 1.5 and 2) were prepared, and the effect of the Ba-doping concentration on the formation was systematically investigated by the Rietveld/XRD quantitative phase analysis. The results show that BaSO₄ is the essential intermediate phase for the formation of the Ba-doped ye'elimite. The solid-state reaction process of C_4-xB_xA₃$ is separately expressed as two main forms, corresponding to the cases in which the Ba-doping concentration (x) is larger than and less than "1", respectively. The Jander diffusion model shows the optimal fitting for C_4-xB_xA₃$ and it clearly proves that the C_4-xB_xA₃$ formation becomes increasingly difficult as the Ba-doping concentration increases. The correlation between the apparent activation energy (E_a) and the Ba-doping concentration is positively well related, which can be expressed as 'E_a) =71.9x+304' (kJ/mol).