Phase profiling of carbonation-cured calcium sulfoaluminate cement

Abstract

The present study investigated the effect of CO₂ concentration during carbonation curing on the microstructural evolution of calcium sulfoaluminate (CSA) cement. Carbonation curing was performed for 28 d at 3 % and 10 % CO₂ concentrations. To profile the microstructure, samples were collected from the surface of the cement to a depth of 30 mm on set curing days. At 3 % CO₂ concentration, vaterite and aragonite predominated, and calcite was generated from the recrystallization of vaterite. At 10 % CO₂ concentration, the formation of aragonite was mainly observed, with distinct phase transition from vaterite to aragonite during curing. The delayed CO₂ penetration rate with an increasing depth from the surface led to an increase in the content of calcite and aragonite at 3 % and 10 % CO₂ concentrations, respectively. The phase assemblages of carbonation-cured CSA cement were thermodynamically predicted and compared with the experimental data to elucidate the microstructural evolution beyond the testing timeframe.