XRAY Concrete slabs

[Alwayslearningelec]

Has anyone had to do this. What does it entail? Thanks.

 

[Alwayslearningelec]

I actually you tubed it. Looks time consuming.

 

[mcclary's electrical]

Has anyone had to do this. What does it entail? Thanks.

I haven't actually Xrayed any,,,but I have a subfloor scanner that will locate steel or plastic pipe in 6" of conrete. I've used it several times to find and bond existing steel in concrete

 

[laketime]

have done it but we hired a company to do it. costly and area has to be cleared to do it.

 

[ohmhead]

Well yes we have the area is to be safe cautioned off meaning no one enters this area during Xray time .
Meaning after hours overtime !

The cost is $400.00 US dollars for one shot !Now thats what my company says it maybe less but its not cheap .

When there done you get a picture to scale of the internal piping or what ever is in the slab in that area Xrayed so you can place it over deck area and drill after you mark area .

We only do this if its a post tension deck and we lost or left out a sleeve during construction .

Mostly around a column or beam area lots of post T cables.

But engineer on some jobs if you have a picture of deck a good photo and can show a good view of whats inside before pour with a clear measurement he will and can let you core drill . At your expense if you hit a cable its yours .

But you must have a good document photo of area .

Good drilling !

 

[Alwayslearningelec]

Can a subflor scanner be a cheaper alternative to xraying?

 

[mcclary's electrical]

Can a subflor scanner be a cheaper alternative to xraying?

I've use it to FIND metal. I've never used it to avoid metal. I would be scared to do that

 

[wireguru]

Can a subflor scanner be a cheaper alternative to xraying?

especially in a PT structure (or when theres conduits in the slab, or even scarier I know of one place with an underground parking garage with an open air outdoor area on top with two 5in conduits supplying primary (15kv?) to a several MVA substation in the parking garage embedded in the concrete. So if you drill down from the courtyard in the right place you have quite the problem. Oh, and this is the feed to 2.5 million square feet of office space occupied mostly by law firms) I would want the liability for locating things in the concrete on someone else's shoulders.

$400 is a cheap price to make a potential catastrophe not your problem.

 

[ohmhead]

Well Xray gives you metal and non metal views to scale so you know whats inside with no issues .

Next i actually think a utra sound unit might be our next to replace the old Xray its a lot safer to use but iam just a electrician what do i know .

 

[hardworkingstiff]

$400 is a cheap price to make a potential catastrophe not your problem.

Just make sure you read the fine print of any contract. A GC I worked with hired a surveyor to layout where a fixed pier should go. Surveyor screwed up and it cost the GC about $20K to fix the mistake. Fine print in the contract said the limit of any damage claim against the surveyor was the amount of the contract. We all learned a lesson that job.

 

[Alwayslearningelec]

I've use it to FIND metal. I've never used it to avoid metal. I would be scared to do that

What do you mean? If you find the metal then you can avoid it,no?

 

[ohmhead]

Well what hes saying is you can find metal conduit rebar and a post cable but its not giving the exact size of it like a Xray would bottom line your on your own drilling with this method .

 

[walkerj]

We always sub out coreing over 1".

There is a contractor here that does the x-ray and the coreing so we let him handle the liability.

Like ohmhead says the screw up is yours if you hit something and as he has described before PT cables are no fun to hit.

 

[mcclary's electrical]

What do you mean? If you find the metal then you can avoid it,no?

No,,,,if you detect metal, you know it's right there. If you DON'T detect metal, you may be simply not detecting something that's actually there.


I would use one to find metal. I would not use one to avoid metal.

 

[Alwayslearningelec]

We always sub out coreing over 1".

There is a contractor here that does the x-ray and the coreing so we let him handle the liability.

Like ohmhead says the screw up is yours if you hit something and as he has described before PT cables are no fun to hit.

What are post tension cables.

 

[walkerj]

Sleeves similar to PVC are strung across the slab before the slab is poured and steel cables are pulled through them in order to pinch the slab tight at a later date.

This is done in lieu of rebar.

 

[ohmhead]

Well a post tension cable runs thur a concrete slab or deck at a high tension. Meaning its pulled with at high level like 8000lbs and more . basic cable to pull concrete together under pressure concrete will not crack but can bend and expand .

If one compresses concrete its stronger !

If one drills into it its like a rubber band which snaps it can come up thur slab breaking the surface or it will take a path straight out the end in both directions like a bomb going off .

It can be 25 ft 100 ft to 300 ft or more in length they have a outer jacket of plastic there filled with a grease for movement and corrosion .

The rigid harden steel inside cable its twisted stranded cable like on a bridge tension tie sup cable think 2/0 wire size or 250 mcm in contrast .

The colors of the cable is the type and size there light weight means less steel in structure so thats why they use them.

Let me send you a deck shot of a post cable deck on one of our projects you can see it better.

I can say it in 35 years ive seen two get drilled thur and they can come out on there own with no help if not installed correct meaning they are on chairs and if one of the chairs breaks and its now real close to the slab surface when they pull it ive seen them fly out of the deck and chucks of concrete flying thur the air guys running deck blasting apart .

 

[Alwayslearningelec]

Well a post tension cable runs thur a concrete slab or deck at a high tension. Meaning its pulled with at high level like 8000lbs and more . basic cable to pull concrete together under pressure concrete will not crack but can bend and expand .

If one compresses concrete its stronger !

If one drills into it its like a rubber band which snaps it can come up thur slab breaking the surface or it will take a path straight out the end in both directions like a bomb going off .

It can be 25 ft 100 ft to 300 ft or more in length they have a outer jacket of plastic there filled with a grease for movement and corrosion .

The rigid harden steel inside cable its twisted stranded cable like on a bridge tension tie sup cable think 2/0 wire size or 250 mcm in contrast .

The colors of the cable is the type and size there light weight means less steel in structure so thats why they use them.

Let me send you a deck shot of a post cable deck on one of our projects you can see it better.

I can say it in 35 years ive seen two get drilled thur and they can come out on there own with no help if not installed correct meaning they are on chairs and if one of the chairs breaks and its now real close to the slab surface when they pull it ive seen them fly out of the deck and chucks of concrete flying thur the air guys running deck blasting apart .

That would be great. Thanks Ohm

 

[macmikeman]

I got the whole shebang coring drill set in a gang box. Can core for up to six inch pipes. I haven't used it in years cause it is a whole lot easier and ends up cheaper in the long run to bring in pro's with xray machines and just pay the piper for the cores.

 

[wireguru]

Just make sure you read the fine print of any contract. A GC I worked with hired a surveyor to layout where a fixed pier should go. Surveyor screwed up and it cost the GC about $20K to fix the mistake. Fine print in the contract said the limit of any damage claim against the surveyor was the amount of the contract. We all learned a lesson that job.

ouch. its also to make sure that sub has professional liability insurance. as far as I know general liability doesnt cover the results of a mistake in the job youre doing. For example if youre drilling through a wall and hit a water pipe the general liability is going to pay, but it would take professional liability coverage to pay out in the example you gave.