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RSI- Case Study #3

Use of GPR for Determining Concrete Deterioration  

    A 1.5 GHz ground coupled antenna was used along with ground penetrating radar system to evaluate the amount of deterioration within an aboveground concrete holding tank at an active paper mill. Because of the corrosiveness of the slurry held within the 72 year old tank, deterioration could manifest itself by delamination and/or by surface cracking. Delamination is most likely to occur at  the inner wall where the concrete may be in direct contact with the corrosive slurry, but can also occur at either the bottom or top rebar schedules within the concrete. Surface cracking can indicate surficial stress, caused by the elliptical shape of the structure, as well as more severe voiding/delamination problems.

    Attenuation was mapped and contoured for the tile/concrete boundary and the upper rebar schedule. Deterioration at the concrete surface was achieved by calculating the real concrete dielectric permittivity (i.e. dielectric "constant") from the reflection coefficient of the surface reflector. Attenuation and dielectric information were then compared with visual observations of the data to determine the overall deterioration of the structure, Overall, the curved walls revealed more deterioration, over 25%, while the straight sections of the wall had about 10 to 14% deterioration. Click on the link below for more information about the survey. 

 

Kutrubes, D.L., 2000, Use of a ground-coupled mono-static antenna for determining the deterioration of concrete structures: Symposium for the Applications of Geophysics to Environmental and Engineering Problems, 21-24 February 2000, Washington. D.C., pp. 851-855