Enhancement in chloride diffusivity due to flexural damage in reinforced concrete beams

A multiphysics formulation for chloride diffusion in an RC beam with stress-induced damage quantifying the enhancement in chloride diffusivity due to damage is presented. An experimental investigation involving measurement of chloride profile was conducted on RC beams damaged under applied flexural stress. Numerical simulation of the RC beam is carried out using a two-dimensional finite-element approach incorporating the damage due to the applied stress, chloride binding, and the chloride diffusion in the model. Concrete is assumed to be a perfectly elastoplastic (Drucker-Prager) material and the steel as an elastoplastic (von Mises) material with hardening. Drucker-Prager parameters, cohesion c, and friction angle φ are obtained by calibrating numerical load-deflection (P-Δ) curve to an experimentally determined (P-Δ) plot for beams loaded in flexure. Defining a scalar damage index as the degradation in elastic modulus expressed in terms of total strains, the chloride transport problem is addressed, using an effective diffusion coefficient, D_effd, expressed as a function of the damage index and chloride binding and obtained by calibrating to data for chloride profiles as determined in flexurally damaged beams. Using the expressions for the effective diffusion coefficient, D_effd, the chloride profiles are shown to match the experimentally determined chloride profiles in beams damaged at various stress levels.