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Technical Discussions
Anu
Engineering
USA, Joined Feb 2010, 2

Anu

Engineering
USA,
Joined Feb 2010
2
23:28 Feb-17-2010
Concrete Post Inspection

Hi,

I am looking for a suitable method for inspecting concrete - voids, cracks, delamination.

Self Consolidating Concrete (SCC) will be placed in module between steel plates (1/2” thick plates on either sides). Module dimension = Length-70’ Width-44’ Height-70’. Thickness of concrete inbetween steel plates is approx 2.5’.The steel plates will remain as is after construction and it is steel-concrete-steel sandwich structure. The internal has lots of steel pipe penetrations, mechanical connectors, tie rods, interior rebars, pins etc. One of the reason to select SCC is easy flow between these obstructions.

Looking for Post Inspection methods for concrete placed in between using NDT techniques. Most of the methods researched so far cannot be used as the steel plate deflects the signal away. Also no holes or windows can be cut through these steel walls.

Seeking expert opinion on this topic. Appreciate your help.

Harini

Thanks

    
 
 
Godfrey Hands
Engineering,
PRI Nadcap, United Kingdom, Joined Nov 1998, 291

Godfrey Hands

Engineering,
PRI Nadcap,
United Kingdom,
Joined Nov 1998
291
08:45 Feb-18-2010
Re: Concrete Post Inspection
In Reply to Anu at 23:28 Feb-17-2010 (Opening).

Hi Anu,
This looks like a tough one.
As you mention, most techniques are not going to work because of the steel plates, but I wonder if some of the aerospace techniques could work when taken to this size.
I am thinking in terms of Thermography or Shearography, but these will depend on the coupling of the steel plates to the concrete.
I take it this is for a future project, so perhaps the design can be slightly modified to better facilitate inspection (such as Studs welded onto the steel plates on the concrete side).
Maybe ask some of the Thermographic and Shearographic people as I don't know enough about them myself to correctly give advice.
The other options could be to introduce sensors into the assembly (inside the steel plates) that would give you the required information. Once again I don't know which type of sensors to recommend.
Godfrey

    
 
 
Joe Buckley
Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT, United Kingdom, Joined Oct 1999, 519

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
519
14:44 Feb-18-2010
Re: Concrete Post Inspection
In Reply to Godfrey Hands at 08:45 Feb-18-2010 .

It's far from a complete solution, But ultrasonic testing from the steel should at least be able, by looking at the echo pattern, to confirm that there is concrete in good contact with it on the far side. This would allow you to at least verify complete fill.

You might be able to check for Gross internal voids by a low frequency through transmission, although the logistical issues would be huge.

Given the scale of the structure its probably worth Mocking Up some test pieces and doing some research to see what could be done.

    
 
 
Michel Couture
NDT Inspector,
consultant, Canada, Joined Sep 2006, 829

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
829
15:00 Feb-18-2010
Re: Concrete Post Inspection
In Reply to Joe Buckley at 14:44 Feb-18-2010 .

Anu,

Just to add my comments to what Godfrey and Joe wrttien. Maybe one technique that could be succesful would be Ground Penetrating Radar. I've seen a show on television and there was also an article in a past issue of the CINDE magasine where they where measuring the thickness of ice on road ice northern Canada.

I don't know anything about it, but that's just a taught.

    
 
 
Anu
Engineering
USA, Joined Feb 2010, 2

Anu

Engineering
USA,
Joined Feb 2010
2
15:56 Feb-18-2010
Re: Concrete Post Inspection
In Reply to Michel Couture at 15:00 Feb-18-2010 .

Thank you all for the valuble comments and suggestions.

@ Godfrey – It is for future application but the designer is unwilling to modify the structure. I will look into Shearography which is something I have not come across.

@ Michel – We have looked at UT option. It requires access holes on the steel plates to access one face of concrete.

@ Joe – GPR does not detect voids, cracks and delaminations, moreover the steel plate will deflect the signal.

    
 
 

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