Infrasense, Inc., one of the leading subsurface detection firms in the nation, recently completed ground penetrating radar (GPR) surveys of two parking garage decks in Syracuse, NY; one at a University campus and the other at a hotel. The objective of University work was to utilize GPR to quantify and map delaminated concrete for subsequent repair planning. The hotel parking deck was evaluated with ground penetrating radar to calculate the depth and spacing of the reinforcing steel, and ultimately create as-built drawings to be used by the project structural engineer in the rehabilitation design.
Nondestructive evaluation (NDE) uses a number of techniques to determine potential issues with materials or structural properties, without causing damage to the structure being evaluated. Because these techniques can be applied to a wide range of structures without any adverse effects, they have become a powerful decision-making tool. The type of structure and the condition to be detected dictates what NDE techniques will be most useful in a condition assessment.
Ground penetrating radar (GPR) is an NDE technique that operates by transmitting short pulses of electromagnetic energy into the concrete, using a boxed antenna attached to a survey vehicle or rolled along the slab. These pulses are reflected back to the antenna providing a record of the properties and thicknesses of the layers within the slab. GPR has the ability to detect the depth and spacing of reinforcing steel, and the thickness of concrete slabs. It is able to detect subsurface deterioration of a slab through changes in the radar signal through the concrete. These results make GPR a useful tool in planning preventative maintenance and avoiding severe and costly structural issues down the road.