Tomographic testing provides a means of evaluating the internal condition of concrete structures identifying specific locations of low velocity zones indicative of internal fractures, delamination, honey combing and voids. Two case studies will be presented: Visual inspections of the piers identified possible structural issues with the concrete in 22 of the 33 concrete piers within a 69kV switchyard. Results of Sonic/ultrasonic tomographic testing indicated thirteen of the piers have little to no defects, one pier has small zones of weakened concrete, and eight piers have zones of low velocity weakened concrete, indicative of internal defects. Subsequent testing of four piers after the cosmetic ring were removed verified the cosmetic ring was not bonded to structural core of the pier. Sonic/ultrasonic measurements with tomographic data processing were made on the beam seat of a bridge to evaluate the depth extent of visible cracking. The results of this testing detected small isolated areas with low compressional wave velocity values indicative of open cracking. Sonic/ultrasonic measurements were repeated at the same test locations after epoxy injection repairs and the results indicate the epoxy injection had filled open cracking detected by the pre-injection measurements.

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