Evaluation of the Service Life with Respect to Chloride Penetration

Evaluation of the Service Life with Respect to Chloride Penetration 

When corrosion is caused by chloride ingress, the service life is usually assumed to be equal to the initiation time h = tj. The period of propagation, which may be of short duration, is traditionally not taken into account because of the uncertainty with regard to the consequences of localized corrosion. 

The initiation time ( ) may be calculated as a function of the chloride transport properties of concrete (usually the apparent diffusion coefficient), the surface chloride content dictated by the environment, the thickness of the concrete cover and the critical chloride content determining the onset of corrosion. The arrival of the critical chloride content at the steel at depth x at time t is calculated using Fick s second law of diffusion (Chapter 6). 

Using this type of calculation, it is possible to find values for D pp (assumed constant) which can be used to obtain a particular service life as a function of the thickness of the concrete cover and the critical chloride content C, assuming a fixed chloride surface content C, as seen in Table 11.6 [16]. 

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