Effect of MgO on calcination and properties of belite-barium calcium sulphoaluminate cement clinker with Na2O AND K2O

Abstract

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 % and 22.4 % when the addition of MgO reaches 7 wt. %, 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 7 wt. % 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 C2.75B1.25A3S– 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.