Innovative study of non-steady-state tritiated water diffusion test

The objective of this paper is to propose a new method for testing molecular diffusion in saturated cement materials. A saturated specimen of porous materials was placed between two compartments; the upstream compartment contained tritiated water (HTO) and the downstream compartment a solution without HTO. The activity gradient between the compartments induced a flux of tritiated water through the sample. Usually, the flux of HTO is repeatedly measured by analysing the content of the downstream cell in the steady state. In this work, a theoretical study based on Fick's laws is used to show that it is possible to determine the diffusion coefficient DFick1 by considering only two measurements obtained in the non-steady state, in the downstream compartment of a diffusion cell. A significant saving of time (approximately half) can be obtained. An experimental study of this innovative method is presented.