Repair, Evaluation, Maintenance, and Rehabilitation Research Program. Development of Nondestructive Testing Systems for In Situ Evaluation of Concrete Structures
Final rept. Apr 81-Jun 85
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS STRUCTURES LAB
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An effort was made to develop an ultrasonic pulse-echo system for the investigation and evaluation of the interior of concrete structures. The large pulse-echo transducer fabricated at Ohio State University OSU was obtained for study. Experimental transducers were fabricated and bandwidths were altered and optimized. Transducer area and frequency of operation were determined and various piezoelectric materials were studied acoustic and electrical matching were employed to optimize signal strength and signal-to-noise SN ratio. The final prototype transducers were constructed of lead metaniobate EC-82 lead zirconate titanate PZT-5H. The transducer area and mass was reduced by 90 percent and the SN ratio was increased by 200 percent when compared with the OSU transducer. The pitch-catch prototype configuration was used to successfully measure the thickness of a 9-14-in. concrete test slab with a SN ratio of 18. The system is presently useful for making thickness measurements on concrete pavements and floor slabs. Limited tests have shown that a metal plate and a plastic pipe can be located in a concrete slab of 9-in. thickness or less. Also, a thickness measurement was made on concrete by generating wideband acoustic sonic and ultrasonic energy by an impact hammer and detecting the echoes with a low Q resonant receiver centered at 180 kHz.
- Structural Engineering and Building Technology
- Test Facilities, Equipment and Methods