SB: Re:Fly ash

["Robert W. Tom" <ArchiLogic@yahoo.ca>]

6/25/02 6:27:57 PM, Lori Ann & Keith <keith.la@sk.sympatico.ca> wrote:

>  I thought fly ash was also a safety concern due to the content of heavy
>  metals, yet people use that in stucco at times..with caution probably,
>  right?

>  recipe for portland cement stucco.  Is it 4:2:1  Sand:Portland cement
>  powder:lime, along with a squeeze of dish soap.....and water (of course) to
>  desired consistency???  How does that sound?


Lori Ann and/or Keith;

The use of fly ash will significantly diminish the vapour permeance of stucco 
and will tend to cause the mixperson to add more water than necessary to the mix
(ultimately weakening the stucco and increasing the likelihood of shrinkage 
cracks during drying of the uncured stucco) so for SB walls, it's not a good 
idea to be using fly ash in the mix. As to the incremental safety concerns due 
to heavy metals, it depends upon the source.


Recipes for PC stucco mixes  have been posted numerous times to this List and  
will be found in the early years of the archives but here're a couple from an 
ancient edition of CMHC's "Canadian Wood-Frame House Construction" booklet:

==============================================================================
STUCCO MIXES BY VOLUME

Portland Cement      Masonry Cement     Lime               Aggregate
      1                   ---         0.25 to 1       3.25 to 4 parts per part
      1                    1             -----        of cementitious material   
==============================================================================


The use of soap as an admixture for stucco mixes in California will result in 
the Building Inspector chopping off one's thumbs and a stretch of 5-10 hard 
labour in the hoosegow. (or so the Skillful Meany once told me.)

For a slightly more verifiable reason for NOT using soap admixtures in stucco 
mixes, I'd suggest doing a web search with "Surfactants" and "Stucco" in your 
search engine.

--- * ---
Rob Tom
Kanata, Ontario, Canada
<ArchiLogic@CHAFFyahoo.ca>
(winnow the "chaff" spamguard from my edress in your reply)

Please visit http://www.theHungerSite.com daily



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