PHASE FORMATION MECHANISM AND KINETICS IN SOLID-STATE SYNTHESIS OF Ba-DOPED YE′ELIMITE: THE EFFECT OF Ba-DOPING CONCENTRATION ON C4-xBxA₃$ SYSTEMS

Abstract

Calcium barium sulfoaluminate (abbr. C4-xBxA₃$), one of the special cementitious minerals originated from ye'elimite (abbr.C₄A₃$), has superior hydration and hardening performance. In this paper, a series of C4-xBxA₃$ 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 C4-xBxA₃$ 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 C4-xBxA₃$ and it clearly proves that the C4-xBxA₃$ formation becomes increasingly difficult as the Ba-doping concentration increases. The correlation between the apparent activation energy (Ea) and the Ba-doping concentration is positively well related, which can be expressed as 'Ea) =71.9x+304' (kJ/mol).

Keywords

• c4-xbxa₃$
• ye'elimite
• kinetics
• rietveld
• solid-state reaction