Effects of different alumina carriers on the phase formation and mechanical properties of sulfoaluminate cement clinker

Finding alumina carriers that can replace bauxite to produce sulfoaluminate cement (SAC) is a significant issue. The effects of bauxite (Ba), industrial aluminium hydroxide (I-AH), industrial aluminium oxide (I-AO) and analytically pure aluminium oxide (A-AO) on the phase formation and mechanical properties of SAC clinkers were studied by differential scanning calorimetry/thermogravimetry, Rietveld quantitative analysis, scanning electron microscopy/energy dispersive spectrometry and isothermal calorimetry. It was found that sintering SAC clinker with Ba and I-AH as alumina carriers accelerated the rate of the solid-phase reaction, promoted the formation of the target phase and led to the formation of ye'elimite with a small grain size. The compressive strength at each age was thus higher. However, when amorphous alumina was used as the alumina carrier to sinter SAC clinker, the solid-phase reaction rate was slow, which hindered the formation of the target phase, free alumina appeared and ye'elimite with a large grain size was formed, so the compressive strength at each age is lower. Aluminium oxide with finer particle size can be decomposed from I-AH and Ba during calcination, which can accelerate the solid-phase reaction rate and promote the formation of the target phase. The associated element in Ba (titanium) can lead to the formation of more α′_H-C₂S, but obstructed the formation of ye'elimite.