Dielectric capacity, liquid water content, and pore structure of thawing–freezing materials

A capacitive sensor-based experimental approach is worked out to study the ice/water phase change in cohesive porous media subject to freezing and thawing. This technique relies upon the dielectric properties of liquid water, ice, air, and mineral substrate in the radio-frequency range. A semi-empirical method based upon the Lichtenecker model and combining drying and freezing tests provides an accurate estimation of the liquid water content versus the temperature in freezing cement pastes. This estimation is further analysed with the help of thermoporometry concepts in order to characterize the pore size distribution and the specific surface area. The results range in the same order of magnitude as those assessed from gravimetric sorption/desorption isotherms.