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CaCl and RH correlation?

#1
I've been using the pounds from Calcium Chloride to determine my moisture content of my slab. How do I determine what relative humidity levels I need to use to correlate with the pounds from Calcium Chloride?

Thanks for your help.

Bryan Fernandez
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#2
Bryan,
There is no correlation between the CaCl2 test and the RH test. Cacl2 tests measure the moisture vapor emissions rate MVER. The RH test measures the internal relative humidity.
Rayt
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#3
So if the manufacturer is calling out to use a CaCl2 test, am I going to be okay with doing relative humudity testing instead?
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#4
Bryan,
It seems like to me, you may not have a choice. From the information that I have been reading in trade journals I’d be leery of trusting the results. If I was in your position I would probably contact the manufacturer and present the case for using relative humidity testing instead. I have run in to a similar situation and was able to proceed with the RH testing.
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#5
As manufacturers collect the test data, they are discovering the RH probe has better accuracy, with fewer potienial errors than the the CaCl2 testing. Several have gone exclusively to the RH probe and I expect more to follow.
Regards,
Rayt
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#6
Hello all !
I would like to introduce myself.
I am a independent flooring inspector just getting started out.
I have over 17 yrs exp. in the floor covering industry living in Dalton, Ga.
My exp. is in the Mfg and claims analysis side of the carpet industry.
I have been an independent inspector for just over a year.
In my first year I have poured a ton of $$$ into tools and training.
This money spent includes the cost of a grinder, diamond cup wheels and dust collection equipment for prepping CaCo moisture testing sites.
I wholly agree that RH testing gives a far superior picture of the real MC of a concrete slab.
Until all the major manufactures of adhesives and floor coverings accept RH readings as a viable substitute or replacement for the old CaCo tests, I must still submit readings in Lbs of vapor emmision per sq ft.
I honestly think the lack of commitment from the MFG's to commit to RH testing is due to the lack of hands on data and the inability to convert vapor emission rates into Rh.
The flooring industry in general is slow to commit to new technology until it has been tried and tested.
Personally as an inspector CaCo testing is very expensive time wise as I have to travel to the site, grind off sealers and wait 24 hours, place tests and record times, then return within 72 hours to record results.
In addition I place data loggers recording temp and Rh of the site to insure the site has not been compromised. PAIN IN THE NECK process that I have to charge a lot of money for that most contractors don't want to pay for and therefore usually don't have the testing done.
Many Installers nowadays don't have the time or resouces to do these tests and will state it is the contractors responsibily to insure the slab is ready to recieve floor covering.
Thats enough for now, just my 2 cents worth.
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#7
These are two different tests completely. I do both and then explain what the results mean to the principals.

Be cautious when grinding floors to conduct CaCl tests!!!! This is not in the ASTM, and for good reason.

If you come upon a floor that has a mitigation barrier installed, you may very well remove it with a grinder and get erroneous readings.

You may remove a natural moisture retarder, the steel trowelled surface of the slab.

If you remove a lot of concrete, say 1/4" or more, you will get a much different reading.

My preparation is as the ASTM states, remove foreign substances to a clean slab. I also often prepare the slab as the flooring contractor will prepare the floor. If he will sand the concrete, so will I.

This is where the RH test will help you determine the potential of moisture in the floor. If you have a hard trowelled floor and get very low MVER, but your RH readings are quite high, advise the principals that the moisture will work through the hard concrete surface over time, and there is plenty of drive to make sure it does.

Conversely, you may get a high MVER and have low RH values. Perhaps the floor was flooded a few days before you placed the CaCl test, and you are reading the wet top layer. In this case you could tell the principals that the slab is actually dry but the surface should dry off for a few days with fans or dehumidifiers.

These two tests are both important!
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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#8
Quote:This is where the RH test will help you determine the potential of moisture in the floor. If you have a hard trowelled floor and get very low MVER, but your RH readings are quite high, advise the principals that the moisture will work through the hard concrete surface over time, and there is plenty of drive to make sure it does.

Where is this scientific data cc? I'd like to read it.
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#9
Ernesto Wrote:Where is this scientific data cc? I'd like to read it.

I will get that for you Ernesto. There is so much available information from CTL labs on this subject I will be able to get it rather easily. Right now I am just checking in between jobs and need to run.

Consider this scenario and you will realize how this can happen.

Water moves through concrete quite slowly. If you have a slab with no vapor retarder and you run heat and dehumidifiers over the slab for a long period of time, you will dry the surface out while the bottom will be still very wet. A MVER test may provide acceptable readings at the surface.

By putting a homogenous flooring on the slab you more or less lock in the moisture, not allowing much to escape at all. With a lot of moisture at the bottom of the slab, and drier concrete above, water slowly wicks into the upper horizons of the slab, and unfortunately carries alkalinity with it.

Have you ever placed a plastic sheet on a slab and found the slab darker after a few days? That's moisture moving through the concrete, trying to get out.
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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#10
Dude..err....Sir, I happen to have a copy of Dr. Goran Hedenblad's book :The Drying of Constuction Water in Concrete; Drying Times and Moisture Measurement.

Can you explain figure 76 on page 44 for me?
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