Evaluation of Nondestructive Testing Methods to Assess the Condition of Concrete Bridge Decks

Abstract

Bridges are critical parts of the transportation infrastructure in the United States and throughout the world. During their lifecycle, reinforced-concrete bridge decks can experience distresses and defects in the form of corrosion of reinforcing steel, delaminations, vertical cracking, honeycombing, and concrete degradation, all of which can compromise a bridge’s structural integrity if not monitored and addressed. Nondestructive testing (NDT) provides a method for surveying reinforced-concrete bridge decks without causing damage to the structure (i.e. coring), and can provide means to track the deterioration of the bridge decks. Developments in technology throughout recent decades have made NDT methods more reliable, time-efficient, and cost-efficient, driving departments of transportation to consider using NDT methods for surveying and monitoring bridges under their jurisdictions.

Five NDT methods were assessed in this project for use by the Alabama Department of Transportation (ALDOT): impact-echo, ground penetrating radar (GPR), half-cell potential, surface resistivity, and infrared thermography. Through research and testing of each method, it was determined that the impact-echo method was most effective and most suitable for use by ALDOT, as it proved to be the most precise, accurate, and time-efficient during testing in the laboratory at Auburn University’s Department of Civil and Environmental Engineering.

A full-scale bridge deck NDT site was constructed for ALDOT at the National Geotechnical Experimentation Site in Opelika, Alabama. In order to determine which defects to include in the full-scale test site, research was performed to determine the most suitable method for replicating common types of defects that occur in reinforced-concrete bridge decks. Methods that accurately represented defects in the laboratory experimental program were used to create defects within the full-scale bridge deck NDT site. This full-scale NDT test site can be used to conduct NDT training, calibrate equipment, and evaluate new NDT methods.