Page 125 - Construction Waterproofing Handbook

3.14 CHAPTER THREE
repellency capabilities of penetrating sealers. In addition, UV degradation affects the life-
cycle repellency capabilities for both film-forming and penetrating sealers. Accelerated
weathering testing, ASTM 793-75, is an appropriate test to determine the capabilities of
a sealer to perform over an extended period. Be sure that the testing is used on a similar
substrate, however, as the alkaline conditions of concrete are more severe that masonry
products.
Of course, it is always appropriate to test for the compatibility of the sealer with other
envelope components and on the exact substrate on which it will be applied. This testing
will ensure that there will be no staining of the substrate, that the sealer can penetrate suf-
ficiently, and that the sealer does not damage adjacent envelope components such as glass
or aluminum curtain wall etching and sealants, as well as surrounding landscaping.
Appropriate field testing methods are reviewed in Chap. 12.

Acrylics
Acrylics and their derivatives, including methyl methacrylates, are film-forming repellents.
Acrylics are formulated from copolymers of acrylic or methocrylic acids. Their penetration
into substrates is minimal, and they are therefore considered film-forming sealers. Acrylic
derivatives differ by manufacturer, each having its own proprietary formulations.
Acrylics are available in both water- and solvent-based derivatives. They are frequently
used when penetrating sealers are not acceptable for substrates such as exposed aggregate
panels, wood, and dense tile. They are also specified for extremely porous surfaces where
a film buildup is desirable for water repellency.
Acrylics do not react chemically with a substrate, and form a barrier by filming over
surfaces as does paint. Solids content of acrylics varies from 5 to 48 percent. The higher a
solid’s content, the greater the amount of sheen imparted to a substrate. High-solids mate-
rials are sometimes used or specified to add a high gloss or glazed appearance to cemen-
titious finish materials such as plaster. Methyl methacrylates are available in 5–25 percent
solids content.
Most manufacturers require two-coat applications of acrylic materials for proper cov-
erage and uniformity. Coverage rates vary depending on the substrate and its porosity, with
first coats applied at 100–250 ft /gal. Second coats are applied 150–350 ft /gal. Acrylics
2
2
should not be applied over wet substrates, as solvent-based materials may turn white if
applied under these conditions. They also cannot be applied in freezing temperatures or
over a frozen substrate.
Higher-solids-content acrylics have the capability of being applied in sufficient millage
to fill minor cracks or fissures in a substrate. However, no acrylic is capable of withstand-
ing movement from thermal or structural conditions. Acrylic sealers have excellent adhe-
sion when applied to properly prepared and cleaned substrates. Their application resists the
formation of mildew, dirt buildup, and salt and atmospheric pollutants.
Acrylics are available in transparent and opaque stains. This coloring enables hiding or
blending of repairs to substrates with compatible products such as acrylic sealants and
patching compounds. Stain products maintain existing substrate textures and do not oxi-
dize or peel as paint might.
Acrylics are compatible with all masonry substrates including limestone, wood, aggregate
panels, and stucco that has not previously been sealed or painted. Acrylic sealers are not