Evidence of variable diffusivity of ions in saturated cementitious materials

Evidence of variable diffusivity of ions, in both the steady and transient states, in cementitious materials are presented. In steady-state diffusion, the diffusivity of an ion, D, is related to the square root of its concent ration up to at least about 0.4M, if not higher. In transient-state diffusi on, the relation of D with concentration is more complicated. Some of these complicating factors have been delineated. Ion profiles in cementitious ma terials can be analyzed without the simplifying assumption of a single diff usivity coefficient. (C) 1999 Elsevier Science Ltd. All rights reserved.