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