Use of barium carbonate to inhibit sulfate attack in cements

The present study aims to explore a new approach to producing sulfate-resistant cements by the addition of BaCO3 to clinker, capitalising on the capacity of Ba to immobilise sulfates in the form of highly insoluble barite (BaSO4). The study conducted on white clinker pastes and mortars with 10 and 15 wt.% BaCO3, analysed the effect of the addition on the durability of materials exposed to external sulfate attack (4 wt.% Na2SO4 for 5 months at 21 °C), as well as on their mineralogy and microstructure. The promising findings show that the presence of BaCO3 improves sulfate resistance by inhibiting ettringite growth. The mortars prepared with high C3A clinker, sand with no fines (to favour the attack) and 15 wt.% BaCO3 remained practically unaltered after 5 months in contact with the aggressive solution, whereas the control mortars (clinker + 15 wt.% gypsum) underwent severe deterioration after only 5 weeks.