A test method for measuring chloride diffusion coefficients through partially saturated concrete. Part II: The instantaneous plane source diffusion case with chloride binding consideration

A test method is proposed for measuring chloride diffusion coefficients through partially saturated concrete specimens with well characterized water contents. It includes an experimental procedure for supplying a limited amount of Cl− to the tested concrete surface, and two mathematical models for processing the experimental Cl− content profiles obtained at selected diffusion times. The use of the more refined model, taking into account the chloride binding by concrete, allows to increase the reliability of the determined diffusion coefficients. For the two tested Portland cement concretes, (water/cement ratios 0.6 and 0.5), the Cl− diffusion coefficient decreases about two orders of magnitude, from 6 · 10− 12 to 2 · 10− 14 m2/s, when the relative humidity of the atmosphere in equilibrium with concrete is lowered from 95% to 54% approximately.