Relationship between coulomb and migration coefficient of chloride ions for concrete in a steady-state chloride migration test

A steady-state chloride migration test with a constant electrical potential drop of 15 V was conducted with a saturated 100 mm diameter x 50 mm long concrete specimen. The migration coefficient of chloride ions for concrete was calculated using the constant flux on the basis of the Nernst-Planck equation. Electrical current was simultaneously monitored throughout the entire period of the migration test. Initial and final coulomb values were separately defined and calculated using the current recorded in non-steady-state and subsequently in steady-state conditions with respect to chloride migration, respectively. A unique relationship existed between the initial coulomb and the migration coefficient depending on the binders of the concrete mixes, that is ordinary Portland cement (OPC) alone, OPC plus fly ash or OPC plus silica fume. However, it appeared that the final coulomb related linearly to the migration coefficient, irrespective of the water.-cement ratios, binders and curing periods.