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Test time for RH test
01-08-2010, 01:30 PM
Post: #11
RE: Test time for RH test
Hello Ernesto,

Let me clarify please. MVER will not vary wildly if measured appropriately. Changes in atmospheric conditions will have an effect on MVER though, so it can change. Proper testing is done under controlled atmospheric conditions. The greatest change I notice in vapor emission rates is after concrete has equilibrated under a flooring material.

Concrete that dries from the top only will have a drier upper horizon after several months of drying, and MVER tests may be acceptable. When a vapor restrictive flooring is placed on the slab the moisture in the concrete redistributes over time and the top horizon becomes wetter than it was when initially tested for MVER. This is especially noticeable when there is a blotter layer under the concrete or there is no vapor retarder under the slab.

The RH in-situ test method will show the potential a slab has for causing problems. It shows us the relative humidity inside the slab. Through testing and many years of real world experience we know that when the relative humidity is below 75% we will not have a moisture related flooring problem. Oftentimes a manufacturer will even accept 80% RH if they have had success at that level.

The RH test is not swayed by a polished slab surface, sealers, atmospheric humidity, and is not as susceptible to temperature swings as a CaCl test is. It is a much more stable test, and as such is in my mind much more trustworthy. I can easily cause false readings with a MVER test, but cannot cause an RH test to be inaccurate when conducted properly. Side by side in hundreds and hundreds of tests I have conducted, RH is accurate and dependable.

Please do not be confused by RCConcrete's statement that RH varies 5% per 2 degree variation in temperature. While this is somewhat factual for a small band of temperatures, if it was a true statement overall then we would go from 100% RH at 32 degrees to 0% humidity at 82 degrees. Obviously this is false. We also want to conduct our RH tests at the service temperature of the floor we are testing. Floors that are on grade are quite thermally stable, and even raised slabs usually vary only a degree or two.

RH testing is extremely accurate and gives us a better picture of the true potential of concrete.

JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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Messages In This Thread
Test time for RH test - jigar0896 - 09-01-2009, 09:38 PM
RE: Test time for RH test - Joe Greenberg - 09-03-2009, 04:03 PM
RE: Test time for RH test - Blake McFee - 09-04-2009, 08:51 AM
RE: Test time for RH test - CC Solutions - 12-17-2009, 11:01 AM
RE: Test time for RH test - CC Solutions - 12-18-2009, 09:53 AM
RE: Test time for RH test - CC Solutions - 12-28-2009, 08:09 AM
RE: Test time for RH test - Ernesto - 01-08-2010, 10:29 AM
RE: Test time for RH test - CC Solutions - 01-08-2010 01:30 PM
RE: Test time for RH test - Ernesto - 01-12-2010, 09:40 AM
RE: Test time for RH test - CC Solutions - 01-13-2010, 07:14 AM
RE: Test time for RH test - Ernesto - 01-13-2010, 11:27 AM
RE: Test time for RH test - CC Solutions - 01-15-2010, 09:36 PM