Acoustic Nondestructive Testing and Measurement of Tension for Steel Reinforcing Members: Part 2 - Field Testing

PURPOSE: This Coastal and Hydraulics Engineering Technical Note (CHETN) describes the field testing of a nondestructive, acoustics-based technique for measuring tension in steel reinforcing members. Specifically, the technology application addresses the problem of determining tension in concrete-embedded pre- and post-tensioned reinforcement rods. BACKGROUND: Many reinforced concrete structures contain embedded pre- and posttensioned steel members that are subject to corrosion and fracturing. Corrosion of steel components can lead to loss of tension and consequent severe problems such as cracking of the concrete or fracturing of the steel. The major problem with existing tension-measurement techniques is that they use indirect, non-quantitative methods to determine whether there has been a loss of tension. We have developed an acoustic technique and transducer to make quantitative tension measurements in a tensioned steel member embedded in concrete. Acoustic waves are nondestructive. They can travel long distances through engineered structures and can be used to thoroughly interrogate a structure s integrity. Acoustics are dual purpose: they can determine bulk material properties, such as tension, and they can detect small defects, such as fractures. Measurements can be performed very quickly, usually in real time, although postprocessing may be required. In this Technical Note, the field testing of a technology application that addresses the problem of determining tension in the concrete-embedded pre- and posttensioned reinforcement rods used in large Civil Works structures is described. A companion Technical Note, ERDC/CHL CHETN-IX-37 (Part 1 Theory), describes a theoretical basis for bulk tension measurements and an acoustic propagation model.