Abstract
Horizontal cracks have been recently found in cut cross-section of deteriorated reinforced concrete slabs of highway bridges in Japan. The horizontal cracks exist at the interface between additional concrete and existing concrete and at the location of reinforcing bars in existing concrete. The existence or development of horizontal cracks is difficult to be detected by visual inspection on the top or the bottom surface of RC slab. Establishing a nondestructive evaluation method to detect horizontal cracks has therefore been required. In this study, impact elasticwave method was performed at the bottom surface of RC slab cut from an existing highway bridges to survey the horizontal cracks. Before measurements by impact elastic-wave method, impact response analysis was applied to determine optimal steel ball diameter, distance between impact point and receiving point of elastic-wave, and frequency analysis methods to calculate frequency spectrum. Efficiency of analysis-aided impact elastic-wave method was confirmed by drilling and observing the interior of the RC slab by stick scanner. Evaluation results by this method agreed well with results of visual inspection. Thus, validity of the analysis-aided impact elastic-wave method on detection of horizontal cracks in RC slabs of highway bridges was demonstrated.
