Troxler Nuclear Moisture-Density Gauge Capacity 5

[milanov]

I am having trouble finding the surface area a troxler gauge can provide a good reading for. I had read somewhere that it was 10,000 square feet but I thought that sounded high. Does anyone know if this is true or not?

 

[Ron]

That makes no sense at all. The surface area, under the backscatter mode, is essentially the footprint of the gage. For direct transmission mode, surface area is irrelevant.

If you are looking for how much surface area a single density test represents, it can be anywhere from a few hundred to several thousand, depending on what your specifications require. As an example, it is common to do one test for each 500 square yards of pavement, per layer. This works out to be one test for each 4500 square feet of surface area, per layer.

 

[milanov]

Thanks a lot Ron. I was looking for the surace area it represents.

I am still pretty new to the quality control field. Are there any good rules of thumb to use if specifications are not readily available?

 

[Ron]

milanov...not sure what your position is, but be sure that you understand the differences between Quality Control, Quality Assurance, and Quality Verification.

Yes, there are rules of thumb for a variety of testing issues...

Concrete - 1 sample set for each 150 cy
Density - 1 in each footing or 1 per 2000 sf of surface per lift, but in no case less than 3 tests in any area

For any other issues, test at a rate of 10% of the issue.

 

[TDAA]

Ron gives some pretty good advice.

Only disagreements are you should always have the full footprint under the gauge.

His second post is good rules of thumb, but I would add that the required frequency should be checked first in the project specs, then your companies rules of thumb, then what Ron has provided here.

 

[eea]

This is a statistical confidence question rather than one of the device. The DOT's usually have this boiled down to a once per X type spec, but it is based on a confidence level derived from having X passing samples per unit of area.

The gauge is like a geotech boring; you now know only the properties of / under the area of what you just tested. Even at that, the gauge's measured density will still have some variation from a core sample run in the lab.

 

[fattdad]

There is no substitute for direct visual evaluation during earthwork. A qualified geotechnical engineer or engineering technician should be watching the earthworks and observing via sight and feel the nature of compaction, the moisture content and the character of the completed fill. If the contractor is directing fills from multiple cuts and the nature of the fill is variable as the width of a pan, then that would require a different measure of testing than a site where the contractor was placing dense-graded aggregate from a stone quarry. I'm not saying, can the specs, I'm just saying not to limit the work to some divine number that you learn from this forum or the spec book. Reason must prevail.

10,000 sf is very typical for a typical QC program. That said, if widely variable, the owner's interest would be better represented by more-frequent testing (providing you have an appropriate Proctor value to use - that's often where the body's buried).

f-d

¡papá gordo ain’t no madre flaca!