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We're almost at 3lbs MVER, so what if the rH is over 90% ?
07-25-2012, 10:28 AM
Post: #13
RE: We're almost at 3lbs MVER, so what if the rH is over 90% ?
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.

JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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RE: We're almost at 3lbs MVER, so what if the rH is over 90% ? - CC Solutions - 07-25-2012 10:28 AM