Assessing reinforced concrete bridge decks using nondestructive testing

This study evaluates multiple non-destructive testing (NDT) techniques for assessing an aged reinforced concrete bridge deck under field conditions with limited access. Ground-penetrating radar (GPR), ultrasonic pulse echo (UPE), impact echo (IE), a cover metre (Profometer), rebound hammer testing, and selective core sampling were used to assess subsurface conditions, reinforcement layout, slab thickness, and concrete quality. Core samples and laboratory compression tests provided ground truth for validating NDT results. GPR identified reinforcement and corrosion-related anomalies, while UPE and IE estimated slab thickness. The cover metre measured near-surface reinforcement depth and spacing, and the rebound hammer estimated in situ concrete compressive strength. Comparative analysis showed that GPR and UPE produced the most accurate slab thickness estimates, with mean absolute errors of 0.255 and 0.209 inches, respectively, compared with core measurements. GPR reliably detected reinforcement and corrosion-related signal distortion, although moisture and embedded girders affected some responses. UPE provided consistent thickness measurements, whereas IE showed greater variability because of its sensitivity to wave velocity, coupling conditions, and concrete heterogeneity. The cover metre accurately mapped only the upper reinforcement layer, while rebound hammer results closely matched laboratory compressive strengths. The integrated workflow improved diagnostic reliability, reduced uncertainty, and minimised invasive testing, providing a practical framework for bridge deck assessment, particularly for structures lacking design documentation.