As soon as water saturation is achieved, the sample is subjected to a water flow, under controlled pressure conditions. Liquid is injected, at a constant pressure Pi, by a high-pressure pump (Gilson type) from calibrated capillary tubes (3 mm diameter). Such a device has the advantage that the injected flow can be measured with high accuracy and, as soon as a steady state flow is reached, it can be easily recorded. Furthermore, it is a direct measurement of the permeability, under steady conditions, which is carried out and based on the entry flow rate Q measurement. As the flow can be assumed to be laminar and the material fully saturated with water, Darcy’s law is applied and leads to: