(07-19-2012 12:40 PM)Ernesto Wrote: JD, your beginning to sound like the guy in the orange shirt. I kid, I kid!! But you, you talk in circles. First you speak of MVER, then jump to water and back to moisture??? How is water MVER?
Water isn't MVER, but without water there would be no moisture emission now would there? So when you test for moisture emission, what do you know? Just about nothing. You have no idea what the slab is like, you don't know the potential for problems down the road. I can tell you I have seen many projects with MVER readings below 3lbs/1000/24 fail, but I have never seen a failure with a slab at 75%rH.
Actually ASTM F-1869 has said to lightly grind the surface for awhile now.. I think, hey is that as bad a drilling a hole in the slab looking for....... ? I have the ASTM dating back many many revisions and I have never read where it says you should lightly grind the surface. Please post that quote here.
So, tell me how long does it take the moisture vapor to move from the 40% level in a 4 inch slab to top and then out the top depending on surface openness? How about one inch? How much difference is one inch depth to 1.6 inches? That much? They say a cacl test only to one inch and on a 4 inch slab why would there be so a discrepancy in numbers?
You don't understand rH readings! The 40% depth has been shown to be the depth that represents the equilibrated rH of the slab. Manufacturers across the globe have determined that a slab that equilibrates at 75% poses very little risk for failure over the long run. (for the record, the CaCl test is only testing the very dry top 1/4" of concrete, and only if the slab is properly prepared, which I have never seen.... ever).
Tell ya what, when all these experts put there money where their mouth is and guarantees the floor when tested with their infallible device I will buy into that.
I know at least one manufacturer that guarantees their flooring based on the rH reading if the readings are Wagner Rapid RH! They will ONLY recognize rH readings, they won't even let you install their floors using a CaCl test. They are also the largest rubber flooring manufacturer in the world.
Now when testing with in situ we are testing for hidden rh down in the slab, right? So if there is excessive rh down in the slab and equilibrates to the surface what does it do that is bad for floorcovering? Make the surface highly alkaline? Is it the pressure only or does it create high mver? If high mver then why not test for mver? Or are we testing for alkalinity or
The rH isn't hidden, it's just where it always is. The multitude of failing slabs that read perfectly fine using CaCl has lead us to find a new and better measuring stick for concrete readiness.
High slab rH indicates the potential for failure. It could be alkalinity that eats your glue, it could be osmotic blisters. It could be ASR destroying your slab! High moisture slabs are a ticking time bomb. The point is you won't have any of these issues with a 75% rH slab, but we have seen thousands of these problems with slabs that passed the CaCl test.
I think you have found your calling. You should write articles for the flooring trade magazines.
I know.... There is a gap in the knowledge concerning concrete and flooring and I am spreading the word.