lonentransport und Beständigkeit zementgebundener Werkstoffe im Kontakt mit Wasser / Ion transport and durability of cement-based materials in contact with water

Cement-based materials undergo a complex interaction whenever they are exposed to water or aqueous solutions. Differences of ion concentrations are the driving force for ion migration into or out of the material. In this contribution hydrolysis is dealt with as an example for the interaction of cement-based materials with water. It is shown that among other processes Ca²⁺-ions diffuse out of the porous structure of the material. As soon as the total amount of Ca(OH)₂is dissolved locally CSH-phases are attacked. The second part deals with Na⁺and K⁺ion diffusion out of water saturated concrete. It is shown that a two-step model describes this process adequately. The effective diffusion coefficient of ion transport is a sensitive indicator of the durability of cement-based materials.