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Ambient humidity vs. RH

#11
How is the Relative Humidity actually being measured? I assume that there is not a trained ant inside the probe doing using a tiny sling psychrometer. And it appears that conductivity of the concrete is not being measured. So how is the RH actually being measured? If I have entered into an area of proprietary secrets, I apologize, but I could not find an answer on the rest of the web site.

Ed Blake (also from Wisconsin)
(10-06-2011, 06:43 PM)CC Solutions Wrote:  
(10-06-2011, 05:16 PM)Rubensgt40 Wrote:  I've been enjoying your work as a spectator for some time, JD. Thanks for the response.

Well it is quite obvious you are an extremely intelligent man Rubensgt40, by the way do you mind if I put your quote on a t-shirt that I can give to my compadres here on the forum?? Tongue

I believe you have the idea down pat already. Do you have any friends you could bring on the forum? Big Grin

As for regional differences in acceptable RH levels, I have not experienced such a thing. I do know that 75% is regarded as safe in the states, but I also know it is very safe in the areas I work. I haven't seen problems at 80% and probably never will. Maybe even 85% would work, but one must keep in mind that ignoring the manufacturer's recommended installation parameters will most likely void any warranty on the materials.
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#12
Hello Ed,
Glad to have you here!

RH can be measured inside the concrete using a number of probes on the market, but of course our favorite is the most accurate and easiest to use, the Wagner Rapid RH.

A hole is drilled into the concrete and a probe is inserted. The probe is left to acclimate to the concrete and once that is complete a reader is used to gather the relative humidity and the temperature of the interior of the slab.
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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#13
(10-10-2011, 11:37 AM)CC Solutions Wrote:  Hello Ed,
Glad to have you here!

RH can be measured inside the concrete using a number of probes on the market, but of course our favorite is the most accurate and easiest to use, the Wagner Rapid RH.

A hole is drilled into the concrete and a probe is inserted. The probe is left to acclimate to the concrete and once that is complete a reader is used to gather the relative humidity and the temperature of the interior of the slab.

Yes, but here in Australia we send the ants in after the probe is acclimatised because they don't like waiting Smile
The problem with socialism is that you soon run out of other people's money.
- Margaret Thatcher

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#14
Are there openings for ant trainers in Oz? I have developed my own curriculum and have trained some world renown ants in the 'lost-quarter-under-the-vending-machine-retrieval' field. RH measurement training would be easier... Tongue
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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#15
(10-10-2011, 03:47 PM)CC Solutions Wrote:  Are there openings for ant trainers in Oz? I have developed my own curriculum and have trained some world renown ants in the 'lost-quarter-under-the-vending-machine-retrieval' field. RH measurement training would be easier... Tongue

Our ants are pretty smart, but impatient as I said before. But hey, come down and have a crack at it! We're thinking of letting them run the country also. Can't be worse than <censored:political rant>

On a less silly note- can I clarify something in the ASTM, which has no doubt been discussed/debated/argued at length here (sorry, I don't have all the required copies just yet): Do your standards call for only in-situ RH testing at 40% depth, or is the hood method still allowable to determine RH?

Or is the method itself simply a manufacturer-spec decided thing, while us folks still debate wildly about the merits of each?

I ask this because I just noticed our draft standard (still under public discussion) refers only to RH determined at 40% depth and references ASTM2170.

This may be problematic where under-slab heating is popular in the colder states and nobody wants to drill.

Any similar thoughts/ problems/ observations from the US?
The problem with socialism is that you soon run out of other people's money.
- Margaret Thatcher

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#16
Fantastic questions Exclamation

The method of testing used is determined by the product manufacturer's recommended limits for installation. So if a manufacturer requires 5lbs MVER, a calcium chloride test would be conducted.

Here in the states many manufacturers are finally moving toward RH testing because they have experienced the failures and questions CaCl testing creates.

I always perform RH tests, even if the adhesive or flooring manufacturer doesn't recognize them. If a floor reads 3lbs MVER and 90% RH I know the floor has a high potential for failure and is not acceptable no matter what the MVER is.

On slabs with in floor heating I have drilled probe holes, once by accident and I got lucky, and once by determining the tube locations by observation (again probably lucky). Another time I failed the slab because there was a blotter layer poured and the slab was below grade, so why even bother reading RH, and only twice have I used the hood. The problem with the hood is the same as the CaCl test, it doesn't indicate the potential the slab has to fail, it doesn't show what is inside. And manufacturer's don't recognize it.

I don't know if your standards will have a spec for drilling 20% depth on slabs drying from both directions... You haven't mentioned that so I thought I'd point it out. Wink
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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#17
Thanks as always, JD.

I was only referring to base slabs. Now that I check the draft again, it doesn't refer at all to suspended slabs and the 20% depth. If ASTM2170 does, then since our draft references ASTM2170 I suppose it's okay. Confused

You're saying that the manufacturers decide the method, but do they also decide the acceptable RH level?

One of the chaps consulting on the draft copy told me that was the favoured idea. But our draft says "concrete substrates are considered sufficiently dry when measurements taken at 40% depth ...do not exceed 75% RH". So the standard is king.

Yet, it also stipulates a PH test, and says "allowable PH shall be as specified by the adhesive manufacturer."

I really hope the consultation period for our draft is extended!
The problem with socialism is that you soon run out of other people's money.
- Margaret Thatcher

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#18
When I say the manufacturer dictates the method of testing, that is for their warranty purpose. So yes, the manufacturer also determines what it believes an acceptable reading is before installation can start, and what the levels must not exceed for the life of the floor.

There are those who don't consider the manufacturer's input and believe if they measure a slab using their preferred method and it passes their test the concrete is ready for them. What that can do though is alienate the manufacturer if there ever is a problem. They will most likely wash their hands of any liability once they find that their parameters were disregarded. And I have seen in a court of law that judges will also exonerate a flooring or adhesive manufacturer when the facts show the installer did not follow the manufacturer's guidelines for installation.
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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#19
Understood, JD. I'm still getting used to the dynamics of universal standards, how they are set, and how manufacturers respond and to what level they are involved.

The way I see it, the standards should set a "starting point" for methods and levels, and the manufacturers should have the option of setting their warranty levels based on their own research with the standards used as a cross-reference.

Here, Most of the folks involved in developing the standards agree that the manufacturers should set their levels, but are not convinced they've done enough of their own research, and are simply copying what's done elsewhere. Mind you, since the US seems to be way ahead of us, bouncing off some of your manufacturer levels is not a stupid idea. Many of the products and technology are US sourced anyway.
The problem with socialism is that you soon run out of other people's money.
- Margaret Thatcher

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#20
Well here it's not always that way. If a manufacturer says he will warrant a product if you do X, Y and Z and there's no standard or the standard differs, you probably want to go with the manufacturer so you retain the warranty.

Then there are the installers who kind of do their own thing and don't follow the standards either because they are ignorant of the particulars or they just don't care. In those cases, I hope you follow the standards because when the job blows up it will show at least you used common sense and followed proven methods.
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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