Concrete Technical Bulletin ||
New concrete contains water, some of which evaporates through the surface. Before any coating system is applied, the wet concrete must be permitted to cure (age) for as long as possible in order to reduce the moisture content. For slab-on-grade not subject to freeze-thaw cycling, 28 days is generally considered and minimum curing time prior to coating. These 28-day periods assumes an average or mean drying temperature of 70°F. In the winter and early spring a typical 6’ Portland cement concrete slab should be allowed to cure for 60 days.
Removal of Efflorescence
If concrete has efflorescence, remove all deposits by wire brushing and acid etching with phosphoric acid. Rinse all surfaces with clear clean water to remove any remaining residue.
In problem areas where there is a need for alkali resistance, apply an acrylic alkali resistant primer. On porous walls and decks use a latex stain blocking primer.
If walls and or decks are slick and smooth use Ty-Zon Primer rather than latex stain blocking primer. Refer to Product Data on Ty-Zon Primer (page 24).
What Is Alkali?
The stiff deposit that can form mostly on masonry surfaces such as concrete. Alkali can eat right through coatings that are put over a surface that contains it.
What Is Efflorescence?
Efflorescence is a fancy word for the term “salting”. Coatings will peel as a result of “salting”. Efflorescence is the crystal-like salt deposits that form on masonry surfaces. It is usually a light gray or white crystal deposit or powder. It occurs when salt like crystals or alkali in the internal part of the masonry surface dissolve and then travel to the surface when water evaporated from the masonry surface.