Chloride induced-corrosion of reinforcement in composite concrete structures

Abstract

This research deals with diffusion of chloride in a double layer composite structure having overlay as the first layer and main concrete structure as the second layer. The present study applies the equation of diffusion of particle in conjunction with Fick’s law to determine the time to initiate corrosion of reinforcement as well as the influence of the depths of overlay and concrete cover of reinforcement upon the initiation time of corrosion.   The Laplace transform technique is utilized to solve the problem with the assumptions that perfect bonding exists at the interface between the two layers; the thickness of the main concrete layer is much thicker than the first layer so that the problem can be modeled as semi-infinite medium; diffusion coefficient in each layer is constant and not a function of time; the chloride concentration at the outer surface is constant and does not change with time. The validity and accuracy of the present solution are verified analytically and numerically with the existing solution of the single layer by assigning a small thickness value in the first layer.