Possible to locate rebar without exposing concrete surface? 3

[JustGettingStarted]

I have been asked to determine the location of rebar on the interior side of a second story concrete exterior wall without removing the concrete coverings. (The building itself is is a fully occupied apartment building).

The interior side of this 18cm thick reinforced concrete wall has 2cm of insulation board, an approximately 1 air gap and then finally 2cm thick drywall. There is no other steel, wiring, piping or even drywall studs present (glie bonding was used) The rebar that needs to be located is within 6 com of the surface of the concrete, 11cm of the surface of the drywall. So the question is whether it is possible to locate the vertical and horizontal positioning of the rebar in the concrete without first removing the drywall and insulation covering the concrete. If so, which detector technology other than perhaps x-ray would be able to do this? I was thinking magnetic based detection but cannot find any documentation on this use case.

 

[STrctPono]

We operate several different types of scanners in our office. Hilti PS250 and PS1000. I am fairly certain that neither of those will work for your situation. The biggest issue being the presence of the air gap. The PS1000 is based on GPR technology. I am not 100% sure what technology the PS250 is based on. You can always reach out to your local Hilti rep or call a company like PenHall (if you have them in your area) and ask them what they think.

 

[Canuck65]

Look for covermeters. Most of them will be able to detect rebar at 11cm depth as long as there is nothing magnetic between the scanner and the rebar.
Some companies that make these devices are:
- Elcometer (Protovale)
- Proceq/Profoscope
- Hilti
I have used many different types at various companies I have worked for in the past. Currently do not have one, but we have been able to rent one on occasion. The equipment that performs reasonably well are all reasonably expensive (as opposed to the low cost stud finders that claim to be able to locate rebar, but generally do not perform well, especially in the circumstances you describe).

 

[Ron]

If you can get a reading at all, it will likely not be accurate, particular the size and depth of the rebar. We have GPR, a Hilti Device and a Proceq device. All work well directly on concrete, but fail miserably when there's an air gap or materials in non-bonded contact with the concrete.

 

[LittleWheels]

Hopefully your rebar is widely spaced as detection becomes very difficult as the bar spacing approaches the cover depth.