Blisters in a Floor Coating? (It’s Probably NOT From Heat


It’s nice to have all the time in the world to get things done.  But you can bet a construction contractor does not have that luxury.
For construction work to remain on schedule, a contractor has to have all the work completed on time . . . one sub-contractor has to have his work completed on time so another sub-contractor can start. 
But suppose the ground at the construction site is a little more wet than usual and the newly poured concrete is much slower to dry.  And suppose for the project to stay on schedule, the floor coating that is specified has to be installed before the concrete is completely dry.  Well, now there is a potential problem brewing.
If the concrete pour included a vapor barrier and was properly hydrated for 28 or more days, then it might be possible to go on as scheduled.  But if the vapor barrier was damaged or the concrete pour was done without a barrier, and there is enough water drive vapor in the ground trying to escape, then the floor coating may have problems showing up later.
Such situations call for a moisture mitigating system.  Many times, the need for these systems is determined by a failure (blistering or delamination) of the coating system, which is a very expensive way to find out.  A much less expensive and very easy way to reach a determination is through a vapor transmission test (ASTM F1869-04 and F1907-04).
The mitigating system to use is often based on the required finished appearance and budget.
Moisture Mitigating Systems (Sherwin Williams/General Polymers is one) consist of a primer and slurry coat of specially blended polymers which act as a sponge to absorb moisture when the vapor drive is high and return it to the concrete substrate where the pressure is low (much like a control bladder in a water tank).
A Respirable Coating System is a coating that breathes and allows moisture to be dispelled through its permeable surface.  These systems are usually much thinner and less expensive than the Moisture Mitigating System but the choice of finished appearances are limited.
For vapor transmission tests and additional information and choices, give us a call at 706-883-6239 or go to our website at www.blackwells-inc.com.

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