Non-steady-state chloride diffusion coefficients obtained from migration and natural diffusion tests. Part I: Comparison between several methods of calculation

The calculation of non steady state chloride diffusion coefficients by migration tests is a quite controversial subject due on one hand, to the complexity found in describing the penetration of chlorides and on the other hand, to the fact that the different researchers calculate them by different procedures. Therefore, in present work, experimental trials have been carried out performing migration tests following ASTM C1202-91 procedure, and modified by applying 12 Volts. Results from migration methods have been compared with natural diffusion results from tests that were performed in two different experimental conditions. From these tests, calculations of non-steady-state diffusion coefficients, Dns, have been carried out, resulting that migration tests give results in the same order of magnitude than those obtained from natural diffusion tests. However, as it is not known how far the diffusion tests reproduce the real conditions, it has been concluded that, in the lack of a reference method reproducing realistic conditions, either diffusion or migration tests cannot be used more than for comparative purposes. Further research is needed on development of tests able to reproduce real performance.