Application of the Nernst-Einstein equation to concrete

Theoretical application of the Nernst-Einstein equation to the determination of diffusivities of aggressive ions in concrete, establishment of rapid tests for the permeability of concrete, monitoring the corrosion of reinforcement, and predicting the service life of reinforced concrete structures are mainly discussed. It is shown that (1)When the transference number of an ion is known or designated to be approximately 1.0, the diffusivity of this ion in concrete can be easily obtained from the Nernst-Einstein equation by measuring the partial conductivity of this ion or the total conductivity of the concrete; (2)The permeability of concrete can be evaluated by the conductivity of concrete when saturated with concentrated salt and the Nernst-Einstein equation is employed. (3)Corrosion of reinforcement can be easily monitored or predicted by measuring the concrete conductivity change, when the Nernst-Einstein equation is combined with the corrosion mechanisms. (4)If the reinforced concrete structure is to be designed durable for more than 100 years, the diffusion coefficients of chloride and oxygen should be no larger than the magnitude of 10(-9) cm (2)/s, and the thickness of the concrete cover and the diameter of reinforcement should be no less than 25mm and 10mm, respectively. (C) 1997 Elsevier Science Ltd.