Ceramics-Silikáty 61, (1) 6 - 13 (2017)

Ba-bearing calcium sulfoaluminate (C_2.75B_1.25A₃$) is characterized by rapid hydration rate and volume stability, as a constituent of the low-CO₂ alternative clinker. In this paper, the effect of K₂O and MgO on the formation and hydration activity of Ba-bearing calcium sulfoaluminate was studied. Results show that according to DSC-TA curves 0.5-0.8 wt.% K₂O can reduce the decomposition temperature of CaCO₃ about 10-23 °C and the decomposition temperature of C2.75B1.25A3$ about 10-16°C. And 4.0 ∼5.0 wt.% MgO can reduce the decomposition temperature of CaCO₃ about 10-23°C and the decomposition temperature of C_2.75B_1.25A₃$ about 10-16°C.The effect of MgO on hydration activity of C_2.75B_1.25A₃$ is a little better than that of K₂O. This may be due to the reason that MgO, especially at the optimum dosage of 3.0∼ 4.0 wt.%, favors the formation of C_2.75B_1.25A₃$ mineral with little impurities such as BaAlO4 which is obtained from the analysis of XRD. From the released hydration heat rate and cumulative heat release results it is found that 0.5-1.1 wt.% K₂O and 2.0-4.0 wt.% MgO promote the hydration of C_2.75B_1.25A₃$ because of the lattice distortion and defects. Appropriate amount of MgO (2.0-4.0 wt.%) and K₂O (0.8 wt.%) can improve the compressive strength and ensure it steady growth with the increase of curing ages. But 1.4 wt.% K₂O and 5.0 wt.% MgO caused BaSO₄ and BaAlO₄ to extend the hydration of C_2.75B_1.25A₃$ and reduce the compressive strengths at both early ages and late ages.