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Old 02-20-2012, 07:20 AM  
ConcreteTreat
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Join Date: May 2011
Location: Branford, CT
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Good morning, Dick!

I found my article -- it was published on PCI: Paint & Coatings Industry Magazine on September 2004, titled "Acrylic Latex Paints: Still the Gold Standard for Exterior Performance."

The quote is:

"The limitations of vinyl acrylic binders in this regard have been well documented. Latex paints based on vinyl acrylic emulsions are notoriously unable to cope with high alkalinity (pH³9). When they are applied to fresh masonry, the combination of high pH and ambient water can hydrolyze the vinyl acetate portion of the binders, causing the coating films to deteriorate badly (Figure 1). The adverse effect of alkalinity - "alkali burn" in paint vernacular - on vinyl acrylic paints makes their use on fresh masonry very risky. Only when enough time has passed for the masonry to become more neutral - as long as a year or more - can they be used reliably. Alkali burn can also be a problem later in the life of the coating if water from the soil or air manages to penetrate the masonry in some way (hydrostatic pressure, cracks or faults in the construction, breaks in the coating, etc)."

So you are ABSOLUTELY right -- it is the ALKALINITY, not the acidity, that is the issue here. I did make a leap in assuming that if paint binders were compromised, others could potentially be as well.

So, yes, I feel sheepish. My thanks and apologies! I'll also be updating an article I'd recently written on the subject, where I mention the acidity level.

Thanks again, sir -- your shared knowledge has saved me a little embarrassment outside of the forum. :-)

~Jacques


Quote:
Originally Posted by mudmixer View Post
I welcome your investigation. Acid and alkalies are two totally incompatible compounds and come from different materials and processes.

Obviously, all materials expand and contract depending on the temperature and moisture to stabilize.

If there is moisture and a substance (wood), moisture can transmit the moisture to any material, be it wood, fiberglass or other materials that have an affinity for moisture since this is a common factor for all materials.

The article from "NASA" is very narrow and not very complete. Since I worked on many NASA projects for rocket test facilities at Edwards AFB, Canoga Park/Santa Susana, CA and Huntsville there was never a mention of the corrosion or acidic effects of concrete because of the basic materials (cement, calcium based based limestone/dolomite or igneous aggregates), The minute snippet of an article on a NASA letterhead may have been a folly or blown out of proportion. In all of the designs for the launch facilities at Kennedy/Cocoa Beach there was not a concern about acid, but salt water and salt contaminated aggregate was minor concern as it is in all of construction Florida, but not universal.

Dick


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