Determination of Capillary Motion of Water in Bricks Using Neutron Radiography

Vertical migration of water in several porous materials has been directly observed and recorded with the recently installed neutron and gamma radiography facility at the MARIA reactor of Institute of Atomic Energy, Świerk. The density profiles of water in samples were obtained from the optical density of digitised images. A simple model (representing the porous material as the collection of capillary tubes of various radii) has been introduced to describe the liquid transport in porous materials in terms of capillary motion. The equation for viscous movement of water in porous material in presence of the gravitation is proposed. A good agreement of the calculated density profiles for vertical water migration with the data collected for siliceous bricks suggests that the thinnest capillary tubes determine the upper edge of the water density profile.