Mechanism of sulphate expansion II. Validation of Thermodynamic Theory

A relationship between sulphate expansion and crystallization pressure is advanced based on thermodynamic theory. The analysis addresses the principal factors affecting sulphate resistance of cement paste, mortar and concrete in contact with water containing sulphates. Experiments were conducted to validate the theory. Theoretical and experimental results indicate that the most important factor affecting sulphate expansion is the activity or concentration of the reactants resulting in formation of a solid product, for example ettringite, in the pore solution. Temperature is also an important factor. Methods of enhancing sulphate resistance of concrete based on theory and experiment are suggested.