Damage Assessment of Concrete Bridge Decks using Impact-Echo Method

A nondestructive testing program was performed to evaluate the integrity of damaged concrete bridge decks. The bridge decks were removed from a bridge built in 1953 in Charleston, S. C. While the concrete decks were in service, they were retrofitted with fiber-reinforced polymer composite materials to repair the extensive damage suffered during their service lives. In this study, two slabs were nondestructively evaluated in the laboratory using the impact-echo method after the removal of the reinforcement layer. Impact-echo tests were performed concurrently with full-scale static and dynamic load tests. The first slab was statically loaded to failure, and the second was tested dynamically with cyclic loading. Impact-echo tests were performed before and after the loading sequence for each slab and between each application of cyclic loading for the second slab. Results from tests on the statically loaded slab detected a significant reduction in propagation wave velocity after failure, indicating a reduction in the slab stiffness. Impact-echo tests on the dynamically loaded slab quantified the degradation of the slab during dynamic testing. Significant damage, such as cracking, was detected earlier than visually observed and before the slab reached service failure.