Concrete was treated for the removal of chlorides before the zeta potential (mV), zeta, was measured amphoterically to prepare the adsorbent for onward adsorption of silver on it. The Gouy-Chapman theory, which describes the relationship between the potential at any distance (X) from the surface, psi(x), and the potential at the surface, psi(0), was applied to determine the shear plane thickness X-S, and to calculate the surface potential psi(0). The X-S, for a treated concrete particulate was calculated to be 7.0 Angstrom. The psi(0) calculated was equivalent to the measured zeta potential (zeta), psi(x) at high electrolyte concentrations, where in general the surface potential greatly deviates from the Nernstian response. (C) 2003 Elsevier Science (USA). All rights reserved.