Table 5 Comparison of the two GPR parameters (relative permittivity and depth-corrected attenuation of concrete cover) for the condition assessment of concrete bridge decks with asphalt overlays.
Classification | Relative permittivity | Depth-corrected attenuation |
|---|---|---|
Principle | Computed with the amplitude of received EM wave as reflected from the interface of a medium to which an EM wave is emitted | Computed by excluding the attenuation due to distance (geometric and dielectric loss) from the loss (attenuation) of the EM wave transmitted to a medium |
Physical significance | Relative permittivity at A/C interface (Relative permittivity at top concrete of bridge decks) | Evaluation of the attenuation by conductivity of the chloride ion in concrete cover |
Advantages | Evaluates waterproofing at A/C interface (water contents ratio of concrete) Correlated to deteriorated depth (poor waterproofing) | Assess the corrosion environment of rebar due to chlorides penetration Correlated to deteriorated depth (deicer usage condition) |
Limitations | Difficult to assess the deteriorated depth if the concrete bridge deck is not in hydrated state | Need for the consideration of pavement layer condition (thickness and deteriorated or not) Need for the establishment of a standard method of depth correction |
Deterioration evaluation | Assessment of soundness of the waterproofing at A/C interface | Evaluation of corrosion environment of rebar and deteriorated depth of concrete |