Influence of cement, aggregates and chlorides on zeta potential of cement-based materials

The aim of this paper is to quantify the zeta potential in cement-based materials, which is the one of the main parameters of the electrical double layer occurring at the interface between the pore walls and the pore solution during ionic transfer. Measurements of the zeta potential were carried out meaning the electrophoresis technique. It is shown that the tested materials concretes, mortars and cement pastes manufactured with three types of ordinary Portland cement and blended cement (CEMI, II and V, according to European standards) present a negative zeta potential when sodium hydroxide, potassium hydroxide solutions or deionised water are used as a support solution. When sodium chloride is added in the solution, the zeta potential tends to become positive. The inversion of the potential is explained by releases of Ca²⁺ by the portlandite and calcium-silicate-hydrate. It is also demonstrated that aggregates seem to be reactive since they present a negative zeta potential.