Subtronic regularly scans concrete to locate rebar, electrical conduits and post tension cables. The advantages of scanning concrete with GPR, is that it is a low energy non-destructive detection method that does not require local evacuation. The GPR puts out about as much electromagnetic radiation as a cell phone (nothing to do with x-ray radiation).
Rebar is routinely used in concrete or masonry work as steel reinforcements. Many of our clients are advised by the structural engineer to avoid cutting rebar in structural walls or elevated floors. 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 damage to the post tension cables.
Post Tension Cables
Post tension cables are installed during the floor construction. Concrete is poured and cured for approximately two weeks, and then the cables are tightened to increase the tensile strength of the slab. Accidentally 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 we can find a clear area for you to core.
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 Radar is a good substitute for x-ray. There are some sites where radar may not have access. The Radar cart needs to be able to roll at least a foot in order to scan. X-ray produces a visible image of the cables and conduits in the concrete. Radar produces a hyperbolic image of the pipe, generated from graphed values.
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 radar and a line locator. By performing a 3-D scan over the core hole locations with radar we are able to locate the conduits that do not match the rebar pattern. Subsequently, we also scan the hole with a line locator. By using a line locator in conjunction with radar, we are using two different types of technology to help confirm the absence or presence of buried electrical conduit. Together with the radar concrete scan we can offer a solid scanning service.