ABSTRACT
We consider why water (and other liquids) are absorbed sponta- neously into porous materials and how we can describe in measur- able physical quantities the state of water in such a material. Topics include: the definition of water content, how the water content is measured, how water (and other liquids) are held in a porous mate- rial by capillary and other forces; wettability; capillary suction, water retention and the definition of hydraulic potential; how the potential is measured; equations for the potential; the sorption isotherm; and values of the potential for brick, stone and concrete materials.
