Ultrasonic C-scan imaging of post-tensioned concrete bridge structures for detection of corrosion and voids

Corrosion of the nation's transportation infrastructure is a widespread and costly problem. Efficiency, durability, safety, and environmental concerns have made the inspection and structural assessment of these structures a vital issue. The current state of the art in concrete bridge condition evaluation relies on visual inspection. However, deterioration in pre-stressing/post-tensioned strand or tendon condition is not always reflected by distress visible on the concrete surface. Further, the effect of deterioration of pre-stressing/post-tensioned steel is more disruptive than that of mild reinforcement. Strand, due to its high mechanical strength and metallurgical characteristics, is smaller in cross section than conventional reinforcing steel and is proportionally more impaired by loss of section. Methodology for prestressed concrete bridge condition evaluation, therefore, could be revolutionized through the development of accurate, quantitative nondestructive test methods for strand in pre-tensioned and post-tensioned structures. This article presents a new sensing method using ultrasound C-scan imaging for structural health monitoring of post-tensioned bridges. Preliminary results from tests are presented that show promising potential for the detection of corrosion and voids in concrete post-tensioned bridges.