Rebar scanning 4

[milkshakelake]

I'm thinking of getting into rebar scanning. It will be for nondestructively scanning slabs, slabs on grade, footings, and walls. I will call some sales people, but I want to be prepared to weed out the BS, since the equipment costs an arm and a leg. Some questions:

1. Products: Proceq GP8000 (or GP8800) for locating depth of 2 layers of rebar. And Proceq PM8000 Pro for rebar size. The Hilti scanners don't seem as good. Any other suggestions?

2. Is there a way to scan rebar through finishes? I.e. sheetrock, tiles.

3. Is there a way to scan if CMU cells are grouted, and what rebar is in them? I interpreted this thread as saying that the same type of GPR scanner can work, but just want to make sure: Link

 

[milkshakelake]

Talking to sales people, I got answers for #2 and #3 (the answer is yes), just wondering if anyone knows if it's true in practice.

 

[Celt83]

For the possible large equipment investment, I'd see if the sales folks were willing to field demonstrate their product.

I'm making a thing:

http://www.thestructuraltoolbox.com

(It's no Kootware and it will probably break but it's alive!)

 

[Brad805]

We have rented the Proceq before (Hoskin Canada), but I was not the operator. Have you considered that? A demo would be a good plan as well. Hilti will not rent in our market, and I recall they start at $50k or so. I have looked at them at the Hilti a few times at the Conexpo, but never looked much more when I figured out the cost.

 

[skeletron]

When I checked it out a year ago, the Proceq salesperson was very much into giving me a live demo on a real structure. I think it was a bit an upsell attempt and also to show how to work with the software. IIRC there is some component of the system (machine, software) that is rented or subscription based.

I never went for it, though. Couldn't suss out if I was able to get the return (existing SOG and walls) vs. a concrete coring company who would actually need it. Can you let use know if you actually get into using it? I'd love to read some experiences.

 

[milkshakelake]

Thanks for the responses. I'll definitely request a live demo. I haven't considered renting it; will look into that. I'll have to see if the return on the investment is worth it (receiving it, using it on one project, packing it up, and shipping it out).

@skeletron Yes, the software is subscription based, which is kind of irritating. But whatever, my AutoCAD and Office 365 is like that anyway. I have to run some numbers and see if this works out (i.e. how many jobs before it pays for itself). If it does, I'll buy it and let you know my experience. I suspect that for concrete coring companies, a simple Home Depot rebar detector is enough to miss the rebar for coring. If you contact me (there's a hint in my profile), I'll send you the pricing I got. Just don't want to post it publicly for legal reasons.

 

[KootK]

I don't know the answers to you questions but I sure do like your idea. I would love to be able to hire someone to scan who actually knew how to design a slab and really understood what information is required to do a proper evaluation back at the office. I'd market the heck out of that aspect of it if you go ahead with this.

 

[Ingenuity]

I have owned and used numerous GPR scanning systems for over 20 years. My main use of GPR is near exactly what KootK would "love". I do design-build structural strengthening and repair, with a main emphasis on prestressed concrete structures. We scan existing concrete to detect reinforcement to structures that have limited or no existing drawings, then undertake analysis options for repair/strengthening based upon data collected in the field.

But, GPR is only one tool in the tool box. We always do selective probing to verify our GPR results, most especially bar diameter, and concrete cover, and structural depth. So that is something to consider.

GPR will work over ceramic floor tile (assuming the bedding is not too thick, or voided), and sometimes through dry-wall if surface mounted, but if there is an air space between the drywall and say a concrete wall then you shall loose penetration of the signal. Also, on a concrete roof with built-up insulation, it will make scanning results problematic.

GPR can be used to detect grouted/ungrouted cells and reinforcement to CMU.

Other GPR systems to considers is CONQUEST by Sensors and Software (Canadian company), and GSSI (US based company). I am about to upgrade my GPR soon and will probably go with GSSI as they have one of the smallest head units, which is very important when you are scanning next to columns, walls etc. By way of comparison, the HILTI unit - which has 3 antennas in the head unit - has good penetration but the head unit is so large it does not work well in tight places.

PROCEQ (now Screening Eagle) has a reputation of manufacturing great equipment (going back 50+ years, originally Swiss based). I own several of their concrete testing equipment. I trialed there latest GPR unit a while back when their rep sent me a unit to me for a 1 week trial. My main issue with is that PROCEQ requires a wifi/internet connection to connect to the iPad. Many times I am in a basement or a tunnel without wifi, so that was a deal breaker for me.

Third-party businesses who provide such services by the hour (or half-day etc.) typically use technician who have little understanding of structural framing systems. They may be ok for layout some pending core holes or openings, but not suitably experienced to be able to definitely tell you the make-up of the reinforcement systems to any accuracy. Many times I have experienced grossly incorrect scanning results by third-party technicians with minimally draped PT tendons to shorter spans of a long-span floor system. For tech's that charge $250 per hour for GPR scanning I expect them to understand the structural framing systems they are scanning, but at best most only have a general construction background.

We work with several traditional consulting SE's in our areas who have their own GPR and their purchase was mainly for internal use (maybe similar to your intended use), but they seldom provide the service to third-party clients (too much liability) for such little return.

 

[Ron]

We use GPR and have both an older Proceq and Hilti scanners. GPR is more accurate and provides a good graphic representation.

 

[milkshakelake]

@Ingenuity Thanks for the thoughtful and detailed response. I didn't know about those other brands so I'll get pricing on them. It's very helpful. I noticed that these other companies don't have a tool for detecting rebar size. I don't think GPR can detect size on its own. Screening Eagle has a Profometer that can nondestructively get the rebar size; then if I have two layers of rebar with one layer inaccessible, like in a footing, I could compare their relative sizes to get an idea of the size of the second rebar.

For the projects I'm looking at, they're actually buildings I designed but rebar inspection wasn't done, so I'm thinking probes won't be necessary if the nondestructive rebar diameters line up with the specified ones.

Do you have an idea about which brand has the best software? Looking online, Proceq's apps seem to be the best and continually improving but it's subscription based. I'll call the sales to see if the other companies have perpetual license, which I greatly prefer, but that has downsides about continual improvement as well. I'm also concerned about an employee keeping the data organized and "remembering" where the scanning was done, especially for a new field tech or engineer, and a software solution for that would be good.

It's good to know that third party scanning businesses don't really understand structures. That could be a selling point if I proceed with this. Speaking of returns, $250/hour seems pretty good, that's more than I charge for engineering, but there's probably a lot of backend with processing the results and making reports.

 

[milkshakelake]

Update: I did not buy it. I ran the numbers. For what is approximately the price of a new Toyota Corolla, it would take a lot of projects, marketing, and "synergy" with other design work to cover the initial cost.

 

[IRstuff]

Update: I did not buy it. I ran the numbers.

I think that's often the case, unless the convenience factor is an overriding concern; the alternative is to hire or rent.

Such situations occur with people resources as well; it takes a lot of consideration to have full-time "specialist" on staff. Likewise, the fallback is to "rent" the expertise for the short durations, or jobs, that you need them for.

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