ABSTRACT
We take the first steps in applying the theory to situations of practi- cal interest, dealing here with systems of one dimension, We look at capillary absorption as an unsaturated flow process, described by the Richards equation. We use a powerful method of analysis, Sharp Front theory, that provides simple approximate solutions of many important capillary flows of practical importance in construc- tion. We introduce the sorptivity, a material property used in unsat- urated flow theory; show how the sorptivity is measured, and give values for a wide range of materials. Topics include: many examples of Sharp Front theory applied to water absorption and displacement problems, including effects of gravity and pressure; absorption by sphere and cylinder; contact time; the desorptivity; dependence of sorptivity on composition; sorptivity characteristics of cement-based materials; and time-dependent permeability.
