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 degrees 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 degrees C), and progress rapidly for the first 30 days. The reaction follows a different pathway at 65 degrees C than at 25 and 40 degrees C due to ettringite instability at high temperatures. (C) 2013 Elsevier Ltd. All rights reserved.