Can anyone share any experience in performing RH tests in these exterior "unacclimated" environments? Concrete over steel decking precisely.
Hopefully your climate is stable and not fluctuating wildly.... Temperature is a factor of rH!
Well, it's Pittsburgh, what can I say except temp at testing time was my first concern too. But this is no place to do Calcium Chloride tests. I would anticipate performing tests in the late spring thru early fall about the same time and ambient conditions the coating systems are to be applied. So technically, they would be conducted in conditions the manufacturer would recognize as acclimated (for application anyway). Other than that, I can think of nothing else to be concerned with off the top of my head.
I'm writing "blindly" right now because I have not read the manufacturer's literature yet. That's next
Always something new to consider, right?
I would ask the manufacturer for their requirements first. If the coating is quite breathable they may be rather lax in their demands.
Typically though almost any finish requires some degree of dryness be inherent in the substrate. You wouldn't put ceramic tile on a 2 day old slab, but 30 days may be fine.
Determining the dryness is rather easy if the slab reaches a temperature conducive for testing. If the concrete never falls below 90 degrees, the rH can read quite low, yet the moisture present could be rather high. Likewise in the winter a cold slab would read artificially low. This is why we test at a standard expected temperature. Outside that range is going to be very wide spread, but you may get a good idea of comparable rH if you can read the slab around 70 degrees.
If the temperature is moving quickly, you may need to insure your probe and the sensor are acclimated also. Can you shade the area you are reading?
A lot of manufacturers if you call them have unpublished RH limits.
True. I will definitely inquire on that.