Relationship between Migration Coefficient of Chloride Ions and Charge Passed in Steady State

Abstract

A new method is presented for determining the migration coefficient in concrete from a steady-state migration test by measuring the charge passed. The plain cement concrete and concrete containing different types of mineral admixtures (fly ash and slag) with water-binder ratios (w/b) of 0.35, 0.45, 0.55, and 0.65 were used. In this study, the electrochemical technique was applied to accelerate chloride ion migration in concrete to estimate the chloride flux. The chloride migration coefficient for concrete was calculated using the constant flux from the Nernst-Planck equation. The charge passed from the rapid chloride permeability test (RCPT), the nonsteady-state charge passed from the accelerated chloride migration test (ACMT), and steady-state charge passed from ACMT were separately defined and derived. The chloride migration coefficient and the charge-passed values from different conditions were compared. Results for all mixtures show a linear correction between the migration coefficient and steady-state charge passed. For concrete with mineral admixtures, there is no obvious correlation between migration coefficient and charge passed obtained from nonsteady-state conditions.