Effect of pulverized fuel ash, ground granulated blast-furnace slag and CO2 curing on performance of magnesium oxysulfate cement

•CO2 curing improved early age strength and water resistance of MOS cement.•PFA/GGBS improved long-term strength and water resistance of CO2 cured MOS cement.•Adding GGBS presented a more favorable effect than PFA for CO2 cured MOS cement. This paper aims to investigate the influence of pulverized fuel ash (PFA) and ground granulated blast-furnace slag (GGBS) on compressive strength and water resistance of magnesium oxysulfate (MOS) cement with and without CO2 curing treatment. Hydration products and microstructure of typical samples were also evaluated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis-thermogravimetry (DTA-TG), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) facilities. The results showed that compressive strength of MOS cement was decreased by the addition of PFA or GGBS. The CO2 curing resulted in a negative effect on compressive strength of MOS cement other than Portland cements. The decreased compressive strength of MOS cement induced by CO2 curing can be alleviated by incorporation of suitable dosages of PFA or GGBS. Both PFA and GGBS behaved an improvement on the water resistance of MOS due to the formation of magnesium silica hydrate gel (M-S-H gel). Therefore, the coupling effect of PFA or GGBS as partial substitution of magnesium oxide (MgO) and CO2 curing treatment provides a potential method to manufacture MOS cement with higher durability and lower environmental impact.