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RE: wet masonry

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From the 5th edition of the Masonry Designer's Guide:
 
"Concrete masonry units that have become saturated, or have wetness over 50% or more of the surface area, are considered to have unacceptable moisture contents. (Ref 4.1.2)"
 
Reg 4.1.2: "All-Weather Concrete Masonry Construction" TEK 3-1C, TEK Manual for Concrete Masonry Design and Construction, National Concrete Masonry Association, Herndon, VA, 2002
 
There is "more" in the Masonry Designer's Guide about the issue, but that pretty much is as close to a "definition" that I am aware of.
 
The key thing to realize is that you generally do NOT want CMU to be wet.  It can cause shrinkage and bonding issues as well as potentially curing issues for thing like grout (grout is deliberately "soupy" because the CMU masonry will absorb/suck in a lot of the water of grout).  CMU units need not be "bone dry", but the key thing is that a compatible mortar needs to be selected so that you get good bond.  If you have a unit with higher moisture content, then a "drier" mortar is generally more desirable...but if the unit is "bone dry" then a "wetter" mortar mix should be used generally.
 
The opposite is generally true with brick.  Brick is usually coming to the site as dry as it will ever be (the making of a brick does a fantastic job of "cooking" out all the moisture...keep in mind that generally brick are essentially "baked"/"cooked").  As a result, wetting them will generally make working with them easier.  But, the same basic principle applies...you want to make sure that a compatible mortar is used otherwise you will end up with bond problems.
 
HTH,
 
Regards,
 
Scott
Adrian, MI
-----Original Message-----
From: DomDean(--nospam--at)aol.com [mailto:DomDean(--nospam--at)aol.com]
Sent: Wednesday, August 20, 2008 5:40 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: wet masonry

I read the commentary but it still does not really define what would be considered wet.




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