GPR Concrete Scanning

Concrete-Scanning-Wall-compressorTo schedule a GPR concrete scanning job with Subtronic Corporation, please contact us.

Subtronic has the equipment and experience to scan concrete with GPR to locate rebar, electrical conduits and post tension cables. The advantages of scanning concrete with ground penetrating radar (GPR), is that it is a low energy non-destructive detection method that does not require local evacuation. GPR emits approximately about as much electromagnetic radiation (as microwaves) 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 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.

GPR website imagePost 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 into.

X-RAY vs. Radar

Core locations could 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. This is where GPR is a good substitute for x-ray. Additionally, GPR scanning can be performed quickly and marked out for clients in real time. There are some sites where radar may not have access, as the GPR antenna needs to be able to move at least a foot in order to scan. X-ray produces a visible image of the cables and conduits in the concrete. GPR produces a hyperbolic image of the pipe, generated from graphed values, but this data can also be used to create a visible image of any rebar, PT cables, and conduits in a slab (see below).

We are often called to scan proposed concrete core locations for electrical conduits in the slabs. We approach these jobs by scanning the area with GPR and a line locator. By performing a 3D scan over the core hole locations with GPR we are able to locate the conduits that do not match the rebar pattern. Subsequently, we also scan the area of interest with a utility locator. By using a utility locator in conjunction with radar, we are able to 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 slab, and through data analysis, a rebar mesh at 3″ ad 6.5″ in depth are observable.

GPR website image (two layers)

Schedule one of our experienced GPR concrete technicians to work for you by using our contact form.