Dielectric measurements to characterize the microstructural changes of young concrete

The dielectric properties of concrete can be used to characterize the development of the microstructure of the cement paste. During hydration the microstructure changes and so does the amount of water in the pore structure. The different dielectric properties of the pore water and the solid phases can be measured with microwave frequencies. In this paper the dielectric properties of cement and concrete during hydration are discussed. The interpretation of the measurements to microstructure-related properties is shown. The connectivity of the pore system has been related to the conductivity of the cement paste. The conductivity versus strength relationship has been used for a practical application. This application concerns the strength development in young concrete in a non-destructive way. This method of monitoring the strength development has proved to be successful. The practical application is now tested on site.