Abstract

Recent studies on the harmful effects of sulfates on OPC have shown that these salts can be immobilised by conversion to insoluble BaSO4. The response of blended OPC-BaCO3 cement to thaumasite sulfate attack is still poorly understood, however. This study explored the effect of BaCO3 on sulfate resistance in fairly high C3A (>10%) OPC mortars and pastes in the presence and absence of CaCO3. Further to the findings, due to low BaCO3 solubility at 8 °C, the temperature that favours thaumasite precipitation, neat OPC sulfate resistance was only slightly improved. Specimens, particularly mortars with 12.5% BaCO3 and no added CaCO3 (12.5B), deteriorated due to gypsum, ettringite and thaumasite precipitation, although less intensely than the samples bearing other blends. None of the BaCO3 or BaCO3 + CaCO3 blends performed better than the commercial sulfate-resistant cement used as the reference.

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