In the period between 2009 and 2011, MnDOT carried out NDT scanning on 166 bridge decks throughout Districts
1, 3, 6, and Metro areas. Most of the work was carried out with ground penetrating radar (GPR), with infrared
thermography (IR) used to a lesser extent in combination with the GPR. The purpose of this work was to determine
the degree of unsound concrete in each deck so that appropriate maintenance and rehabilitation measures could
be taken to maximize the benefit to users for a given budget. As part of this process, MnDOT commissioned an
independent study to review cost, accuracy, and usefulness of these NDT methods with respect to their estimation of
the actual extent of bridge deck repair. As part of this study, repair work on 12 of the bridge decks was evaluated.
This evaluation included both chain drag areas obtained prior to construction and the footprint of the actual bridge
deck repair area. The paper describes the GPR and IR methodology used in this project, the types of results obtained
from these surveys, the method of gathering the chain drag and final repair quantities, and the comparison between
the GPR/IR results and those obtained from chain drag and repair quantities.
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