Impact of sulfoaluminate cement modification on corrosion resistance of reactive powder concrete subjected to ammonium sulfate-rich sewer environment

Using sulfoaluminate cement (CSA) to partially replace Portland cement (PC) was effective in improving the early strength and eliminating the autogenous shrinkage of UHPC at ambient temperatures. However, the sulfate resistance of PC-CSA blended UHPC has not yet been well understood. This study investigates the effects of adding CSA on the corrosion resistance of reactive powder concrete (RPC) exposed to an ammonium-magnesium sulfate solution. The results showed that the main corrosion products generated in the RPC were gypsum, ettringite, and thaumasite. The addition of 8 wt% CSA significantly improved the corrosion resistance of RPC owing to reaction between CH, ye'elimite, and gypsum that created ettringite, which refined the pore structure and improved the aggregate-paste interface bonding. Specifically, incorporating 8 wt% CSA caused a 13.28% reduction in the porosity of RPC pastes after corrosion. In contrast, excessive adding CSA produced massive gypsum crystals and led to the separation of pastes from aggregates, reducing the corrosion resistance of RPC. At last, CSA modification can be considered as a low-carbon method for the design of RPC materials applied in ammonium sulfate-rich sewage environments. [Display omitted] •Effects of CSA additions on the sulfate resistance of RPC in artificial sewage was investigated.•The RPC gained the best resistance to sulfate attack with 8% CSA replacement.•Corrosion products and pore structures were identified using XRD, TG-DTG, SEM and MIP.•Improvement mechanism by CSA modification was analyzed.