Assessing Deterioration of an In-field RC Bridge Deck by AE Tomography

Deterioration of aging infrastructures is an important issue in many developing and well-developed countries. For maintenance of the infrastructures in limited budgets, proactive inspections and countermeasures are important before severe structural damage occurs. To assess the deterioration of those structures in a reliable and preferably nondestructive manner is highly demanded. Responding to the demand, acoustic emission (AE) tomography can be regarded as a powerful method since it builds the elastic-wave velocity distribution of the medium that AE waves propagate through while simultaneously locating AE sources. Such a method has been widely tested in laboratories but not yet fully realized in fields. In the present study, the applicability of two-dimensional (2D) and three-dimensional (3D) AE tomography techniques to the evaluation of internal damages in existing RC bridge deck was examined using the data obtained by single-side AE measurement. The overlay of 2D elastic-wave velocity distribution with AE source locations reveals that AE was active in moderate-velocity areas and the boundaries of low-velocity areas, which were regarded as deteriorated areas with progressing defects. Moreover, in the AE measurement, a large number of AE with small amplitudes were observed in the severely deteriorated panel; amazingly, primary AEs were captured, which implied the propagation of an internal crack in the deck.