Discussion: Neutron radiography: an excellent method of measuring water penetration and moisture distribution in cementitious materials

The paper by Justnes et al. provides a good illustration of the use of neutron radiography as a method of measuring water distribution in cementitious materials.The results they have given are very interesting and can be analysed further.The absorption of water by porous inorganic construction materials and the movement of water within them can be described by using concepts of unsaturated flow that were first developed in soil physics. 1 This approach is now well established and is being adopted increasingly. 2sing this analysis it can be shown that one-dimensional horizontal flow is described by the non-linear diffusion equation