In order to investigate the hydration mechanisms of the mineralogical constituents of super refractory aluminous cements, the subsystems belonging to CaO – BaO – Al₂O₃ system were initially deduced for their potential performance; the area of the subsystems: C₂BA₄ – CA₂ – SS_CA-BA (C = CaO, B = BaO, A = Al₂O₃, SS_CA-BA = solid solutions CA – BA); C₂BA₄ – CA₂ – BA₆, with reduced content of BA₆; C₂BA₄ – CA₂; C₂BA₄ – BA₆ and CA₂ – BA₆, with reduced content of BA₆; C₂BA₄ – incongruent compound, with its decomposition in BA, CA₂ and CA was outlined in this way. For the selected compositions from these subsystems, containing mainly C₂BA₄ and CA₂, the compounds reactivity and the nature of the formed hydro compounds were deduced. The information regarding the degree of hydration of the mineralogical compounds involved in the various examined subsystems was obtained by X-Ray diffraction performed on hydrated samples, kept at different intervals of time; at the same time the hydro compounds formation became apparent. It is seen that the hydration of the compounds from the studied subsystems is conditioned by BA presence in the system, from the heat released by this particular hydration of the accompanying mineralogical compounds until BA has been used, respectively; after this period it is observed that the degree of hydration of these compounds decreases considerably. In this circumstance, the existence of two phases of hydration is distinguished: one with high hydration speed due to BA presence and another, with lower hydration speed after BA is used. The presence of BA is determined not only by the existence of the reactive baria compounds but also by the synthesis temperature and duration of the thermal treatment. The compositional design of the precursor mixture can be optimized by synthesizing thermal treatment of the super refractory cements; it is also possible that the hydration mechanism can be directed such that its influences are manifested on the binding properties during the hardening of calcia baria aluminous cements.