EFFECT OF MgO ON CALCINATION AND PROPERTIES OF BELITE-BARIUM CALCIUM SULPHOALUMINATE CEMENT CLINKER WITH Na₂O AND K₂O

The High-quality limestone resources decreased sharply worldwide, and MgO-rich limestone, as an important part of low-quality limestone, is widely used in the cement production because of its low cost. The purpose of this study was to explore the effect of MgO (1-9 wt.%) on the composition and properties of belite-barium calcium sulphoaluminate cement with Na₂O and K₂O. The experimental results showed that 1∼3 wt.% of MgO in the mineral composition was in favor of calcining and stabilizing the crystal structure of M₃-C₃S, R-C₃S and β-C₂S in the cement clinker. Furthermore, the addition of MgO evidently increased the content of R-C₃S and β-C₂S and goes up to the highest value of 14.47% and22.4% when the addition of MgO reaches 7wt.%, and the increment of R-C₃S and β-C₂S was beneficial to improve the mechanical strength of the clinker. The 3d, 7d and 28d compressive strength of the cement with 7wt.% MgO increased by about 26%, 7.3% and 36.2% than that without MgO. Meanwhile, since the addition of MgO also can promote the formation of C₄AF, but has little effect on the formation of C2.75B1.25A₃$ and C₃A, the C₃A/C₄AF ratio present significantly reduction, which indicate that MgO can reduce the viscosity of the liquid phase in the process of calcination. So, the utilization of MgO in low-quality limestone has a great potential to develop low-carbon and sustainable society in producing the belite-barium calcium sulphoaluminate cement.