measurement in a cold slab - Printable Version
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RE: measurement in a cold slab - eaadams - 12-20-2012 04:23 PM
@Ernesto context please
RE: measurement in a cold slab - Ernesto - 12-20-2012 06:23 PM
What do you want from me? Ask the ASTM committee or make up your own context like everyone else does.
RE: measurement in a cold slab - CC Solutions - 12-20-2012 07:55 PM
Stephen, where did you get the graphic? It looks like something Bob would have, and it is wrong besides. At least it is wrong in the context you are trying to insinuate.
Without pulling out my psychrometric chart I will go out on a limb and say that graph represents the chart. But concrete RH measurements don't follow the standard chart. I don't know why, and greater minds are working on it.
Service temperature is the temperature the slab will be at during use. Slabs on grade don't vary much, suspended floors can vary quite a bit, especially if the above ceiling space is used as a return air plenum.
RE: measurement in a cold slab - eaadams - 12-21-2012 04:29 PM
(12-20-2012 07:55 PM)CC Solutions Wrote: especially if the above ceiling space is used as a return air plenum.
We did some rubber tile with releasable adhesive over a concrete raised access floor system in the San Francisco federal court house. They use the area under the RAF for air circulation.
Amazingly dry. So dry that it literally dried out the adhesives so much it had no grab.
A sidenote, but that plenum space comment gave me ... flashbacks
RE: measurement in a cold slab - eaadams - 01-18-2013 05:02 PM
Have an odd slab where it is 2" ontop of a bitumin tar like hot mop over a 5-6" structural slab from the 1930's.
tester placed the wagner probes in the 1-1/2" so to not puncture the membrane / tar thing.
Results between 69% - 90% over 13 tests.
Here is my worry: slab temp > ambient temp. Somehow (and I've never seen this) the slab temp in the 50's and the air temp was 49. Ambient RH 57%.
I said I'd like to see readings taken when there is some drive with hotter air in the space (it has been cold in CA this winter). He more or less said hot air won't give good readings since this is the 'ideal' time for such testing with high humidity. I wouldn't call 57% ambient humidity high but...
Do you agree that these cold air temps encourage accurate RH readings in the Concrete?