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+--- Thread: We're almost at 3lbs MVER, so what if the rH is over 90% ? (/showthread.php?tid=307)
RE: We're almost at 3lbs MVER, so what if the rH is over 90% ? - CC Solutions - 07-25-2012 08:25 AM
Valid test? They changed the rules for testing, so now how do we interpret the results? A 3 pound floor may now be a 10 pound floor. If the 3 pound floor was good 6 months ago, is it bad now because we changed the method of testing? It's all hocus-pocus based on no science. This test came from dumping salt on concrete and covering it to see if it got wet. It evolved to specific numbers that resulted in failures, and now the test has changed completely so it has no historical background.
Just consider this: If you have to grind the floor to take a CaCl test you are changing the surface of the slab. You are increasing the porosity of the floor and letting it breathe. You are increasing the MVER at that area. BUT you are NOT grinding the entire slab, you are NOT increasing the MVER across the whole area. You are NOT testing a representative sample of the floor MVER.
What you are trying to do is determine the moisture content of the floor using a test that is outdated and easily swayed by atmospheric conditions.
I say give it up and use the test that is proven to work. Leave the salt to deicing sidewalks and rimming margarita glasses.
RE: We're almost at 3lbs MVER, so what if the rH is over 90% ? - eaadams - 07-25-2012 10:14 AM
(07-25-2012 08:25 AM)CC Solutions Wrote: Just consider this: If you have to grind the floor to take a CaCl test you are changing the surface of the slab. You are increasing the porosity of the floor and letting it breathe. You are increasing the MVER at that area. BUT you are NOT grinding the entire slab, you are NOT increasing the MVER across the whole area. You are NOT testing a representative sample of the floor MVER.
I disagree. We insist on grinding the carbonation off the top if someone insists on CaCl testing.
Why?
... all concrete cracks. Therefore, any part of the slab may be exposed to that MVER in the future.
RE: We're almost at 3lbs MVER, so what if the rH is over 90% ? - CC Solutions - 07-25-2012 10:28 AM
The change in the ASTM was to increase the MVER reading to try and read the moisture trapped in the concrete which was causing failures and the old method of testing wasn't showing it.
Finished concrete (especially when sealed using steel blades) has a lower MVER than open and porous concrete. Grinding the surface removes the layer of concrete that holds back the moisture from escaping and being read by the CaCl test.
The moisture was always there, the old ASTM just couldn't pick it up. Will grinding reveal it? Maybe. Will grinding pack the pores with dust? Yes. Will the readings be definitive? No.
Everything will change with MVER readings. What will work now? Who knows? Maybe if you grind off the concrete sealed cap, a floor will work great at 6lbs. Who knows?
I know I have tested floors where the flooring contractor put down a test where he had just scraped the floor with a razor blade (the old ASTM did not require grinding) and his readings were 3 lbs, but when I ground off an 1/8" of the surface my readings were over 10lbs. The floor had failed, but according to the old ASTM who was right? The un-ground portion was emitting a low MVER, and the entire floor was un-ground. The flooring installer was testing conditions as they were where the flooring was installed.
I, on the other hand, was modifying the concrete surface and getting much higher MVER numbers. Back then you couldn't use my MVER numbers because I modified the concrete to harvest them.
My point is this is all new again, and nobody knows what to look for now.
RE: We're almost at 3lbs MVER, so what if the rH is over 90% ? - Ernesto - 07-26-2012 01:44 PM
(07-25-2012 08:25 AM)CC Solutions Wrote: and now the test has changed completely so it has no historical background.
I've been lightly abrading the surface for years using CaCl tests, no failures, it's got history to me. Then I've also NOT abraded the surface as well, no failures.
Just consider this: If you have to grind the floor to take a CaCl test you are changing the surface of the slab. You are increasing the porosity of the floor and letting it breathe. You are increasing the MVER at that area. BUT you are NOT grinding the entire slab, you are NOT increasing the MVER across the whole area. You are NOT testing a representative sample of the floor MVER.
I used to argue that point about changing the surface structure as well if I wasn't planning on resurfacing it before gluing a floor down. Then I realized it is better to know the higher value.
What you are trying to do is determine the moisture content of the floor using a test that is outdated and easily swayed by atmospheric conditions.
And what test is not influenced by atmospheric conditions? Does it not say in 2170-11 that the havc should be up and running for validity?
RE: We're almost at 3lbs MVER, so what if the rH is over 90% ? - CC Solutions - 07-26-2012 02:33 PM
The HVAC does not have to be running for validity.
You cannot interpret the ASTM's as you feel they should be. The old MVER test never required grinding and never required HVAC. The new 2170 doesn't require HVAC.
If the temp is 70 and the humidity is 50, HVAC does nothing for you.
RE: We're almost at 3lbs MVER, so what if the rH is over 90% ? - Ernesto - 07-26-2012 02:49 PM
ASTM F-2170-11
9. Conditioning
9.1 Concrete floor slabs shall be at service temperature and the occupied air space above the floor slab shall be at service temperature and service relative humidity for at least 48 h before making relative humidity measurements in the concrete slab.
RE: We're almost at 3lbs MVER, so what if the rH is over 90% ? - Ernesto - 07-26-2012 07:27 PM
(07-26-2012 02:33 PM)CC Solutions Wrote: The HVAC does not have to be running for validity.
You cannot interpret the ASTM's as you feel they should be. The old MVER test never required grinding and never required HVAC. The new 2170 doesn't require HVAC.
If the temp is 70 and the humidity is 50, HVAC does nothing for you.
Well, did you actually read the new ASTM or are your making that up?
RE: We're almost at 3lbs MVER, so what if the rH is over 90% ? - Ernesto - 08-16-2012 09:38 AM
(07-26-2012 02:33 PM)CC Solutions Wrote: The HVAC does not have to be running for validity.
You cannot interpret the ASTM's as you feel they should be. The old MVER test never required grinding and never required HVAC. The new 2170 doesn't require HVAC.
If the temp is 70 and the humidity is 50, HVAC does nothing for you.
I'm still waiting for an explanation. If what you say is true about the HVAC running for validity, then why is it not in my 2170-11 standard? Is there an updated one I am not aware of?
RE: We're almost at 3lbs MVER, so what if the rH is over 90% ? - CC Solutions - 08-16-2012 10:46 AM
(07-26-2012 02:49 PM)Ernesto Wrote:
ASTM F-2170-11
9. Conditioning
9.1 Concrete floor slabs shall be at service temperature and the occupied air space above the floor slab shall be at service temperature and service relative humidity for at least 48 h before making relative humidity measurements in the concrete slab.
As you posted ^^^
You do not need a heater or a blower or a cooling system to provide the required conditions. Many facilities are within the stated parameters well before the HVAC system is functional.
RE: We're almost at 3lbs MVER, so what if the rH is over 90% ? - Ernesto - 08-16-2012 02:34 PM
So, most facilities you work in have an ambient rh of 50% with the HVAC running at 70 F ? Hmmm, I have a hard time believing that.