EFFECT OF MgO ON CALCINATION AND PROPERTIES OF BELITE-BARIUM CALCIUM SULPHOALUMINATE CEMENT CLINKER WITH Na?O AND K?O

摘要

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 Na?O and K?O. 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 M?-C?S, R-C?S and β-C?S in the cement clinker. Furthermore, the addition of MgO evidently increased the content of R-C?S and β-C?S and goes up to the highest value of 14.47% and22.4% when the addition of MgO reaches 7wt.%, and the increment of R-C?S and β-C?S 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 C?AF, but has little effect on the formation of C_(2.75)B_(1.25)A?$ and C?A, the C?A/C?AF 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.