Ettringite decomposition in the presence of barium carbonate

The interaction between cement paste and sulfate-rich solutions or soils induces gypsum, ettringite or thaumasite precipitation. These expansive processes may be mitigated by using BaCO3 (witherite) as a setting regulator. The present study explored ettringite decomposition in the presence of witherite at different temperatures (25, 40 and 65 °C) and reaction times (up to 90 days) to further the understanding of this process as grounds for developing new sulfate-resistant cements (SR-PC). According to the XRD, FTIR and DSC-TG findings, sulfoaluminate decomposition and barite formation begin in the first 24 h of the reaction, even at ambient temperature (25 °C), and progress rapidly for the first 30 days. The reaction follows a different pathway at 65 °C than at 25 and 40 °C due to ettringite instability at high temperatures.