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When to Test
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11-22-2009, 11:36 AM #1
CFI Newbie *
Status: Offline Posts:2 Threads:2 Joined:Nov 2009
When testing for moisture in newly poured concrete slabs on a large commercial project ,when is the correct time to start testing to get meaningful readings? I have some job supers wanting me to start testing before all the windows are in! I have heard that the RH in the slab should be in the low 70's - Ninety days after the pour,after the building is tight and the AIR CONDITIONING has been running for 30 days. Not the heat, but AIR CONDITIONING as this removes the moisture from the air which will allow the movement of moisture out of the slab. Is this true? Many Job supers think that temporary heat will get the job done. I have heard that some heaters such as "Salamanders" actually add moisture. Is this true?

I would like to be able to refer to a document that I could give my customers that tells them what is the criteria for meaningful moisture testing and what needs to be done to lower the RH in the slab as quickly as possible.

Is there an authority where I could get these guidelines?

Thanks for your help.

11-24-2009, 12:23 PM #2
Ben Newbie *
Status: Offline Posts:5 Threads:1 Joined:Sep 2008
ASTM 2170 section 9 tells you what the conditions need to be before you take an RH test.

12-16-2009, 11:45 AM #3
CC Solutions Concrete Moisture Evangelist *******
Status: Offline Posts:1,065 Threads:69 Joined:Dec 2009
A byproduct of burning hydrocarbon fuels is moisture, so an improperly vented heating system can add moisture to the slab. However if fresh air is used for combustion this is usually not the case.

I tell people to begin testing slabs as soon as they can! I have installed RH probes in slabs and sealed the top with duct tape to keep water out of the probe when windows were still missing.

ATSM 2170 does have parameters to follow before RH tests are to be accepted as 'gospel' but the information gathered from early testing still has great value. Trending a slab's moisture content can help identify problems long before they become emergencies.

I'd rather tell a general that he needs to shot blast and bring in a dehumidifier system 3 months before he needs to put floor coverings down, than try to tell him that a week before he needs to start.....

JD Grafton
Concrete Answers for Flooring Problems
JGrafton@ccsolves.com








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