GPR Concrete Scanning

Advantage of GPR

  • Low energy non-destructive detection method that does not require local evacuation
  • GPR emits approximately as much electromagnetic radiation as a cell phone (unrelated to x-ray radiation)
  • GPR is routinely used in concrete or masonry work to locate steel reinforcements. (Many of our clients are advised by the structural engineer to avoid cutting rebar in structural walls, floors, or even ceilings.)

Post Tension Cables

Post tension cables are being used more often in home floor slabs and commonly in suspended concrete floors. As contractors are modifying buildings for new tenants (i.e., installing plumbing and electrical runs), it is critical to avoid damaging post-tension cables.

  • Post tension (PT) cables are installed during floor construction. Concrete is poured and cured for approximately two weeks, and then post-tension cables are tightened to increase the tensile strength of the slab
  • Cutting these cables is hazardous and may cause damage to the building
  • Locating PT Cables in the slab is extremely important before cutting, coring, or drilling. By scanning the area with radar and marking out the location of any PT cables, we can find an area free of obstructions for you to core or drill

X-RAY vs. Radar

Core locations can be x-rayed; however, that would require evacuating a 50-foot radius around the core location. If the building you are working in is a hospital or an apartment, you may not be able to clear all the occupants, and this is where GPR is a good substitute for an x-ray. Additionally, GPR scanning can be performed quickly and marked out for clients in real-time.

  • X-ray produces a visible image of the cables and conduits in the concrete.
  • GPR provides a hyperbolic representation of the pipe, generated from graphed values
  • We use this data can also to create a visible image of any rebar, PT cables, and conduits in a slab (see below)
  • We can scan proposed concrete core locations for electrical conduits in the slabs
  • We scan the area with GPR and a line locator. By performing a 3D scan over the core hole locations with GPR, we can locate the conduits that do not match the rebar pattern
  • We also scan the area of interest with a utility locator. By using a utility locator in conjunction with radar, we can use two different types of technology to help confirm the absence or presence of buried electrical conduits

Below is an example 3d GPR scan of a single location for a concrete slab. The GPR was able to collect data through the entire concrete slab, and through data analysis, a rebar mesh at 3″ ad 6.5″ in depth are observable.