Rebar in existing conc wall 2

[JoeBaseplate]

What methods are their available to determine the size and spacing of rebar in a 14" thick conc wall. The arch wants to place a new door in the existing wall and the existing documents do not show any rebar info.

Thanks.

 

[dcarr82775]

X-ray will give you size and spacing although not sure how well it works on a 14" wall. It also is a hassle given safety issues with the X-rays themselves

GPR works pretty well. Spacing is easily determined in each direction, and a good operator can get close on a bar size but they are often wrong on the size. For a 14" wall they would need to scan on both sides, but it is quick to do.

 

[Ron]

Agree with dcarr....GPR is quicker and easier but you'll have to drill in at one or two locations to get the true cover and size. It will locate it for you though.

Yes, radiography can be used (not x-rays, but gamma rays), but 14" of concrete will require a long shot time, thus increasing the downtime of all in the area that will have to be moved out during the exposure time.

 

[strucguy]

Check this out.
We have used this in couple of renovation projects, but as indicated by Ron earlier, it would be a wise thing to measure the true rebar size and cover by exposing rebar at couple of locations.

http://www.proceq.com/products/concrete-testing/rebar-detection/profometer-5.html?pqr=2

 

[Ron]

strucguy...I have a Profometer and use it for this as well, but usually not on large areas as it is relatively slow for large areas.

 

[racookpe1978]

Would liquid magnetic particle inspection show anything - even if only fuzzy impressions of the underlaying steel under the concrete - on the surface of the concrete?

Mag particle is really used for checking for cracks in steel-weld-steel issues where everything is magnetically conductive, but I'm wondering if the liquid particles would react to the magnetic field of the test probe intersecting the bars under the concrete.

 

[msquared48]

Well, when he cuts the hole out for the door, won't the rebar be exposed?

Mike McCann
MMC Engineering