Pore characteristics of calcium sulfoaluminate cement paste with impact of supplementary cementitious materials and water to binder ratio

The main hydration products of calcium sulfoaluminate (CSA) cement were analyzed by X-ray diffraction and thermogravimetry. The pore characteristics of CSA cement paste with the incorporation of different supplementary cementitious materials (SCMs) were studied by a mercury intrusion porosimeter. Water-to-binder ratios between 0.24 and 0.73 were used in the mixtures. The microstructure of the CSA cement concrete was observed by backscattering electron microscopy. The test results indicate that compared with ordinary Portland cement (OPC) paste, CSA cement paste has a coarser pore volume. Silica fume can substantially reduce the median pore diameter (MPD) of CSA cement paste. With the action of SCMs and the adjustment of the water to binder ratio, the pore structure of the CSA cement paste is significantly refined, harmful pores and air pores are greatly reduced. SCMs can play a substantial filling role in CSA cement concrete, which can optimize the pore structure and improve the related properties. [Display omitted] •Compared with OPC paste, CSA cement paste has a coarser pore volume.•Silica fume can significantly reduce the median pore diameter of CSA cement paste.•With the action of SCM, pore structure of CSA cement paste is remarkably refined.