Repair Inspections Using Sonic/Ultrasonic Measurements and Tomographic Data Processing

Nondestructive measurements of sonic/ultrasonic compressional and shear waves can be used to determine the extent of cracking and to identify areas of hidden flaws such as delaminations, voiding or honey combing in concrete structures and structural elements. Sonic/ultrasonic waves which travel through the structure are usually measured at the nodes of a constructed grid. Measured arrival times at each sensor location are input to a tomographic imaging program to contour internal compressional and shear wave velocity values. The tomographic images are used to identify areas with lower values indicative of weakened concrete due to cracking, voiding, delamination or air entrapment such as honeycombing. These results can be used to identify areas for repair and also serve as a benchmark to evaluate the effectiveness of repairs.

The results of sonic/ultrasonic measurements before and after epoxy injection repairs are shown in the figures below. Isolated areas with lower compressional and or shear wave velocity values may be indicative of open (in tension) cracks, these are shown on the Òbefore dataÓ represented on the figure as red and yellow areas.

Sonic/ultrasonic measurements were repeated at the same test locations after epoxy injection repairs. The post repair results (below) are indicative of increased strength, higher compressional wave velocity values.

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