When you think of Ground Penetrating Radar, your first image probably has two features. First, the GPR machine is being used on the ground or a slab floor. Second, GPR is being used to search for something, such as an underground void, piping or even old graves. Not all concrete is located on the ground, however, and GPR’s uses go beyond simply finding objects. This is especially the case when it comes to using GPR for bridges.
There are two basic categories of structural tests for bridge decks: destructive and non-destructive.
Destructive methods include:
While these might be necessary to double-check problems found by non-destructive means, as a starting point these methods present some obvious issues.
Older non-destructive methods also exist, like chain-dragging and half-cell potential. In chain-dragging, a chain is dragged along the bridge deck while a worker listens for a change in sound that would indicate a hollow point in the bridge. This has obvious problems, including a high degree of subjectivity and the potential that outside noise could affect the findings. The damage also has to be advanced before this method is able to spot it.
In half-cell potential, electrodes are used to detect the presence of corrosion in the rebar. This can be an issue when there is any sort of asphalt overlay keeping the electrode from being placed directly on the concrete. It also has limits on the type of information collected and the usefulness over large areas.
GPR, however, does not have these limitations. The results come in the form of data, not subjective characteristics, and GPR can provide more data about the actual corrosion than the half-cell method.
GPR has been proven useful in detecting rebar and concrete damage and areas affected by moisture seepage.
At GPR Arkansas, we have experience with using GPR on not only commercial and residential projects, but also infrastructure projects. Our skilled GPR operators are able to interpret the collected data to identify potential issues and anomalies within a bridge’s subsurface. Contact us to provide our expertise with your infrastructure project.
