Sonic / Ultrasonic inspection data are generated by a projectile impact energy source, an array of sensors and a PC for onsite data display for quality assurance as the data is acquired and to archive the data for future playback and processing. The projectile impact produces stress waves in concrete that are detected by the array of sensors which measure the amplitude of the wave in time (time domain data). Sonic / Ultrasonic inspection data tracks the time required for a compressional and shear wave to travel from the impact point to each of the sensors and the frequency content of the recorded signals. The transmission velocity values determine the mechanical characteristics of concrete, including the Young's, Bulk, and shear modulus values as well as Poisson's ratio and a calculated strength values. These values are principally controlled by the presence of cracking, voiding or weaker strength concrete.
Each reflecting surface (change of density and/or velocity) produces a multi-path reflection in the layer it bounds. These reverberations (echoes) are particularly diagnostic of delamination and thickness of the concrete. They will readily distinguish the presence of local delamination, cracked or decomposed inclusions by the particular frequency band generated at the mechanical discontinuity.
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