Nanostructure evolution of (A/F)H3 phase with different alkali concentrations based on calcium sulfoaluminate cement

Abstract

The effect of different pH on the formation of the synthesized (A/F)H3 phase was characterized and investigated based on calcium sulfoaluminate cement. The results show that the (A/F)H3 phases with different Al/(Fe+Al) ratios at different pH have a crystalline structure and leads to a transition between microcrystalline and well-crystalline structures of the (A/F)H3 phase. Low pH is not conducive to the formation of good crystals, while high pH is beneficial. At the same time, the higher Al/(Fe+Al) ratios leads to the precipitation of AH3 phase crystals in an alkaline environment. In addition, the microscopic morphology of the (A/F)H3 phase changes from a microcrystalline nano-granular to a good needle-like crystal structure at pH = 6–12.5. The substitution of Al leads to a significant change in the particle morphology and agglomeration structure of the (A/F)H3 phase, and the aspect ratio was significantly reduced. At the same time, the specific surface area was also markedly affected.