Effect of strontium oxide on the formation mechanism of dicalcium silicate with barium oxide and sulfur trioxide

Belite-barium calcium sulfoaluminate cement is a new type of cement characterised by low energy consumption and low carbon dioxde emissions, but the slow hydration of the belite phase leads to a slow mechanical property gain at early ages compared with ordinary Portland cement. A doping technique has been proposed as one option to promote its reactivity. Strontium slag, a kind of chemical industrial waste produced from the manufacture of strontium salt, has a high level of emissions in China. In this study, the influence of strontium oxide on the formation mechanism of dicalcium silicate with barium oxide and sulfur trioxide, which are both in excess in belite-barium calcium sulfoaluminate cement clinker, is investigated. Results show that strontium oxide accelerates the decomposition process of calcium carbonate, and its final decomposition temperature can be lowered by 67 degrees C. Strontium oxide decreases the formation rate of dicalcium silciate at the same temperature, but the amount of total dicalcium silicate formed can still be as high as 94.5 wt% at 1350 degrees C. Moreover, it is revealed that strontium oxide plays a significant role in stabilising beta-dicalcium silicate, and reduces gamma-dicalcium silicate by about 40%. This study could lead to environmental benefits and cement performance improvement.