ABSTRACT
This approach has been implemented by the South African National Roads Agency Limited (SANRAL) in a large scale project, the Gauteng Freeway Improvement Project (GFIP) developed to alleviate the current traffic congestion problems in Gauteng Province. The limit value of cover depth for durability requirements in the project is 40 mm for in-situ and precast elements. This value can be linked to the DI prediction model for carbonationinduced corrosion. The outcome of the model (i.e. carbonation depth development with time for the given input parameters) is illustrated in Figure 1. For a structure to attain the required service life, the carbonation depth should be limited to 40 mm, thus the cover depth provision in the specification. The acceptable ranges of cover depth, allowing for tolerance are minimum cover depth of 30 mm and maximum cover of 55 mm.
