Role of permeability in sulphate attack

Abstract

The role of permeability in sulphate attack was evaluated in this study. Resistance to sulphate attack was measured by determining the expansion caused in concrete specimens with exposure to 5% Na 2SO 4 solution. Concrete specimens were prepared from five binders, namely: ordinary Portland cement (OPC), high slag cement (HSC), sulphate-resistant cement (SRC), OPC with 7% silica fume (SF) and HSC with 7% SF. Concrete of grades 35 and 40 were used. The expansions of concrete samples were compared to their permeabilities to establish the role of permeability in controlling the expansion due to sulphate attack. It was found that the relative performance of concretes cannot be explained by either their permeability only or by only the chemical resistance of the binder. However, by combining the information on permeability and the chemical resistance of binder, the relative performance of concretes can be estimated. Thus, both permeability and the type of binder play an important role in sulphate attack.