Ground Penetrating Radar? 1

[shin25]

I am trying to perform a non destructive testing of a building shear wall which is about 20" thick. I was thinking of using GPR (ground penetrating radar) to do the probe. Due to congestion of reinforcing in the wall, I am giving second thought to this GPR, as it will be unable to descern closely spaced reinforcing and reveal the delamination behind them!

Can you guys point me to any other NDT methods that can reveal any structural imperfection in this wall under these circumstances?

Thanks in advance.

 

[bridgebuster]

Thermography might work. I've used it in the past on bridge decks - works very well. I've never used it on a wall but I know it can be done. We were going to use it for a retaining wall inspection. I've heard of building thermography but don't know anything about it.

Keep in mind, thermography won't show the reinforcement only the delaminations but not the depth, and the surface needs to be exposed to sunlight for a few hours. There's a firm in Milwaukee that I've dealt with in the past.

You can use an x-ray but I wouldn't recommend it. There are too many safety concerns to deal with.

 

[Rjeffery]

Ultrasonic Testing (UT) may be an option.

 

[shin25]

Not too sure about ultrasonic, feels like the received wave may be too distored due congestion of reinforcement and thickness of the wall! Am I right?

 

[shin25]

Meant to write 'distorted'-sorry.

 

[Bagman2524]

We're looking a GPR to locate underground facilities on a refinery. Try geomodel.com, bloodhoundunderground.com or thompsonengineering.com. They may have a recommendation.

 

[msucog]

http://www.olsoninstruments.com/all/all.html

 

[LittleWheels]

Impact echo should pick up delam, other methods for picking up reo. What imperfections are you looking for? There is nothing that does everything.

 

[shin25]

I am perticularly interested in voids behind surface, concrete to steel delamination, etc.

 

[Madikins]

The best bet for this application by far is impact echo. GPR (with a 1.5 GHz antenna) has difficulty penetrating reliably beyond about 18 in., particularly with the two mats of steel. Infrared thermography could work to identify front side delaminations, but no way could you see back side delams in a 20 in. wall.

IE would work in the hands of a seasoned NDE engineer, as reflections from a backside delam would be indicated as a thinner section of wall. Areas where the wall is say 15 in. would likely indicate a delam. As always with any NDE methodology, confirmational testing (coring, drilling, etc.) is recommended.