Developments in Ultrasonic Pitch-Catch and Pulse-Echo for Measurements in Concrete

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Title: Developments in Ultrasonic Pitch-Catch and Pulse-Echo for Measurements in Concrete

Author(s): A. Alexander and H. T. Thornton

Publication: Special Publication

Volume: 112

Issue:

Appears on pages(s): 21-40

Keywords: concrete pavements; evaluation; measurement; transducers; voids; nondestructive tests; thickness; ultrasonic tests; General

Date: 1/1/1989

Abstract:
A new improved prototype ultrasonic pitch-catch (two-transducer) and pulse echo (one-transducer) system has been developed for concrete. Signal generation and detection is done with piezoelectric crystals. A literature search revealed that no piezoelectric pulse-echo system had been developed for the ultrasonic range ( > 20 kHz) and that pitch-catch measurements needed further development. No commercial system could be found on the market for making pitch-catch measurements. Research by the U.S. Army Engineer Waterways Experiment Station has resulted in the development of a 200-kHz pitch-catch system with a signal-to-noise ratio of 18 and a pulse-echo system with a SNR of 8. The mass and dimensions of the improved system have been reduced significantly from the prior state-of-the-art system. The WES system works well for thickness measurements of portland-cement concrete pavement and can indicate the presence of voids.