The major purpose of this paper is to use Kirchhoff's transformation associated with Laplace's transformation methods to obtain the analytical solution of the modified Fick's second law of nonlinear diffusion equation with initial and boundary conditions provided by Martín-Pérez et al. [A study of the effect of chloride binding on service life predictions. Cement and Concrete Research 2000; 30 (8): 1215-1223]. Based on experimented data and four kinds of chloride binding isotherm, i.e., no, linear, Langmuir, and Freundlich binding, results of free and total chloride concentration profiles calculated from the analytical solution are presented for a concrete structure suffered from two different exposure conditions: submerged in seawater and exposed to deicing salts during 6 months, 5 years, 30 years and 50 years, respectively. The difference between the analytical solution and the approximate solution obtained by Martín-Pérez et al. used finite-difference method can be represented by percentage error. The percentage errors of Freundlich’s binding are higher than those of no binding and linear binding when both service life and concrete cover increase. The implication of answering for chloride binding in service life predictions is in detail discussed. The result of present study may offer as a critical reference of maintenance, strengthening, and demolition of concrete or reinforced concrete (RC) structures subjected to chloride-ion penetration.

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