Thickness measurements are one of the most common applications for acoustic non3destructive testing (NDT) methods for concrete components such as ultrasonic pulse echoand impact-echo. They become relevant whenever components are accessible from onlyone side and, for example, the design thickness needs to be verified or the geometry of astructure needs to be assessed.While such measurements are relatively easy to conduct on test objects with simplegeometries and wide dimensions, they become challenging when the geometry of the testobject is more complex or when the dimensions of the test object are rather compact.In this study, measurements have been performed on two test blocks with differentgeometries. Block A is a solid slab-like block of mostly constant thickness. Block Bconsists of areas of different thickness. All measurements are conducted using anautomated test frame, thus providing dense scan grids and therefore good statisticalsignificance. Two- as well as three-dimensional imaging techniques are applied to thedata.Within the thickness range investigated here (169 to 510 mm), ultrasonic pulse-echo hasproven to be generally robust even on block B with a rather complex geometry.While impact-echo provides satisfying results on the rather simple slab-like block A, it isseverely affected by geometrical effects when measurements are being conducted on atest block B.
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