cement thickness tester?

[albor2974]

would anybody know of a solution for finding the thickness of cement with some type of a device other than ground penetrating radar ( they cost 20 thousand). I want to be able to be inside of someones house and without messing up the carpet or tile or flooring detect where the thicker parts of the concrete are. Under a cement slab in a house it is either four inches thick or two foot thick where they trenched out for the beams. i need some type of scanning device (similar to like a wall stud finder) that will tell me that the cement is either 4 inches thick or its two foot thick. there is rebar through out the whole slab so metal detectors go bezerk. i found a company that makes a cement thickness tester but you must have contact with the cement so the carpet and tile get in the way. ground penetrating radar starts around 20 grand and it is overkill, because i dont need an image or to find stuff. Im trying to solve this problem for the foundation contractors here i work with and would appreciate any ideas. thank you.

 

[wrsharper]

As a kid we used to check the thickness of the ice on a pond by holding a sledge hammer, bottom down, from about six inches, dropping it and listening to the thud. The lower the tone the thicker the ice.

 

[albor2974]

wrsharper, your right that absolutely works with the hammer. we do that in garages sometimes to find the thicker cement beam. I just wish i had some device that would detect it without damaging the flooring inside the house. would a sonar type scanner work? like used to image inside a womans womb? this is is you EE's area of knowledge. thanks for the input.

 

[Comcokid]

Ultrasonics require that you have an constant acoustic connection (impedance match) to the item you want to measure. Remember that when they do a ultrasound they put a viscous jelly on the abdomen.

I don't thin placing a small pool of silicon grease in the carpet would be acceptable to the homeowner.

For radar, the carpet and padding would behave mostly like air and would have a different response from the concrete allowing you to differentiate just the concrete.

Seems like something DeWalt or Stanley ought to investigate to develop a tool.

 

[OperaHouse]

I remember using a Seamen Nuclear roof moisture meter about 30 years ago. It shot radiation into a roof and would bounce back when it anything with hydrogen, water or tar. We mapped out roofs to find leaks by plotting water absorbed in insulation. It was my first job as a rent an engineer! Durring training they said this instrument was also used to measure soil compaction. Concrete could be considered very compact soil. While it didn't give an actual number, it gave a relative number that would allow you to map a floor and identify thicker sections.

 

[OperaHouse]

How about radiation. 30 years ago I was trained on a Seaman Nuclear roof moisture meter. This bounced radiation off hydrogen. At the time of training they also explained that this was also used in consrtuction to measure soil density. Concrete is dense soil!

 

[albor2974]

thanks operahouse, im lookin into it.

 

[jraef]

http://www.olsoninstruments.com/ctg/ctg.htm

Says it works on bonded tile, but you may need to lift up a patch of carpet.

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[jraef]

By the way, I hope you meant concrete[i/]! Cement is just a component of concrete.

 

[albor2974]

thanks jraef, i did mean concrete your right. And the olson instruments concrete thickness guage would be awesome for my applcation and i would get it, but they told me about 3 months ago, as i was begining this search for a solution, that it will not likely get an accurate reading through most tiles. thanks for the advice.