Ettringite decomposition in the presence of barium carbonate

• Published in: Cement and concrete research Vol. 52; pp. 140 - 148
• Main Authors: Carmona-Quiroga, P.M., Blanco-Varela, M.T.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-10-2013; Elsevier
• Subjects: Applied sciences; Barium carbonate; Buildings. Public works; Carbonates; Cement concrete constituents; Cements; Decomposition reactions; Ettringite; Ettringite (D); Exact sciences and technology; Expansion; Grounds; Hydration; Instability; Materials; Pastes; Precipitation; Properties of anhydrous and hydrated cement, test methods; Reaction time; Regulators; Soils; Sulfate-resistant cements (D); Thermal analysis (B); Thermodynamic calculations (B); Ettringite (D); Thermodynamic calculations (B); Barium carbonate; Thermal analysis (B); Sulfate-resistant cements (D); Ettringite; Hydration; Chemical resistance; Thermogravimetry; Decomposition; Experimental study; Sulfates; X ray diffraction; Modeling; Thermodynamic model; Cement; Thermal analysis; Fourier-transformed infrared spectrometry; C3A phase
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/j.cemconres.2013.05.021

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 90days) 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 24h of the reaction, even at ambient temperature (25°C), and progress rapidly for the first 30days. The reaction follows a different pathway at 65°C than at 25 and 40°C due to ettringite instability at high temperatures.