A method for moisture measurement in porous media based on epithermal neutron scattering

• A new method based on neutron scattering was developed to study liquid transport in porous media.
• An assembly of a Pu–Be neutron source and an array of 4 or 6 He-3 neutron detectors was used.
• Fast as well as slow flow processes in porous media can be investigated.
• Water absorption into clay and silicate bricks, and sand column were carried out.
• The results were discussed in terms of the diffusion theory.

A method for moisture measurement in porous media was proposed. A wide beam of epithermal neutrons was obtained from a Pu–Be neutron source immersed in a cylinder made of paraffin wax. 3He detectors (four or six) arranged in the backward direction of the incident beam were used to record scattered neutrons from investigated samples. Experiments of water absorption into clay and silicate bricks, and a sand column were investigated by neutron scattering. While the samples were absorbing water, scattered neutrons were recorded from fixed positions along the water flow direction. It was observed that, at these positions scattered neutrons increase as the water uptake increases. Obtained results are discussed in terms of the theory of macroscopic flow in porous media. It was shown that, the water absorption processes were Fickian and non Fickian in the sand column and brick samples, respectively. The advantages of applying the proposed method to study fast as well as slow flow processes in porous media are discussed.