Ground Penetrating Radar (GPR) poses no safety hazard due to radiation and can be performed at any time of the day with minimal impact on work. GPR is a reliable non-destructive testing (NDT) method for locating objects (such as rebar, cable, conduit, post-tension cable, etc.) within concrete, but has limitations. GPR is not 100% accurate or effective.
GPR may be limited by:
Congestion in the Scan Area: Multiple layers of rebar, closely spaced rebar, or metal mesh may obscure objects below.
Material Type: Plastics are harder to locate than metal.
Geometry: Objects oriented perpendicular to the scan surface, or nearly so, are harder to locate.
Corrugated Pan-Decking Slabs: These can hide indications in the lower portions of the slab or valleys of pan decking.
Depth: The deeper an object is, the harder it is to locate. Generally, objects below 15" cannot be located with standard equipment.
Relative Location of Objects: One object directly above another may obscure the second object. For example, a rebar above a conduit or cable may hide the conduit or cable below.
Water: Standing water will damage the equipment, and relatively moist, new or "green" concrete will limit the effective scan.
Condition of the Scan Surface: A rough, rugged, or "bumpy" surface may interfere with the ability to correctly or accurately locate and mark objects.
Surface Obstructions: ScanXConcrete requires at least 1 foot of space in all directions beyond the scan area. More space may be required on a case-by-case basis. Scans along walls generally require material removal at the base of the wall. Scans next to existing pipes and conduits are difficult.
Steel: GPR cannot scan through steel. For example, beams and conduits below a steel deck cannot be located from the top of the slab. Also, metal track along wall lines must be removed in order to scan the area below the track.
Layers of Material: High-density foam or thick tar layers between concrete slabs prevent penetration into the lower slab. Objects in the interface between concrete and grade or air are harder to detect by our normal GPR scanning service, but GPR should not be used as the primary means for detection of such objects.
For critical or difficult inspections, a combination of GPR and Radiographic Testing (RT) may be required. ScanXConcrete will advise the client on the optimum application and any possible limitations.
ScanXConcrete is not responsible for delays or costs of any kind incurred by the client due to failure to locate objects hidden in concrete. The client waives all claims for damages, including credit or offset of ScanXConcrete invoices for services related to, or arising from, cutting, hitting, or otherwise disturbing objects within concrete.
The client understands and accepts the statement of limitations for subsurface imaging/GPR inspection as stated in this document.