Research Pays Off: Service Life Modeling: Selecting Repair and Rehabilitation Options for Bridge Structures

Evaluating the corrosion condition of a reinforced concrete structure is essential in developing a strategy for repair and rehabilitation after corrosion-induced damage. Several destructive and nondestructive test methods and techniques are available to ascertain the corrosion condition of the reinforcement in portions that do not yet show concrete damage. Most of these techniques, however, require significant resources to implement and then additional resources to interpret the data and make the decisions about repair and rehabilitation. In response, TRB's National Cooperative Highway Research Program (NCHRP) produced a bridge condition survey protocol, a model for remaining service life, and a susceptibility index to designate the likelihood of corrosion, which were published as NCHRP Report 558, Manual on Service Life of Corrosion-Damaged Reinforced Concrete Bridge Superstructure Elements.

The model and the susceptibility index provide a streamlined mechanism for performing the corrosion condition survey and applying the survey results to determine the future progression of damage and to select the optimal repair and corrosion control system. The service life model allows the owner to perform life-cycle cost analyses of various options according to estimates of the progression of damage.

Service life modeling offers another advantage, by reducing the amount of field data collection and sampling. The model requires only the results of the delamination survey, chloride profile analyses, and a concrete clear cover survey.

The condition evaluation protocol of this model can be integrated easily into the routine bridge inspection. In addition, the model can be used to ascertain future susceptibility to corrosion-induced damage and the magnitude of the damage, so that the optimal corrosion control systems can be installed to reduce or stop corrosion and increase the remaining service life.