All mortar joints and other types of masonry containing high levels of salts should be acid etched with a muriatic acid solution, reduced to a 3-5% solution
with water, in order to eliminate subsequent effects of efflorescence on the coating system. Sufficient material must be applied in order to insure maximum penetration into the masonry surface. After the acid etch has been allowed to dry, a high-pressure water rinse should follow in order to insure that all salt formation has been removed from the masonry surface. If salt crystals remain on the masonry surface, the water rinse must be repeated in order to remove these deposits. It may be necessary to repeat this etch-rinse procedure to pacify
the concrete surface and eliminate signs of efflorescence. A properly etched surface will display a roughened surface profile, a complete removal of all concrete surface dust, and either no reaction or only a very slight foaming reaction when a subsequent coat of acid etch is applied to the surface.
Smooth surface areas of tilt-up or precast concrete should be prepared with an acid etch, or preferably a light brush blast in order that complete pacivity of the surface and subsequent penetration of masonry coatings is achieved. It is especially important to remove form oils and release agents present on the concrete surface. This procedure should also be followed on any masonry surface, including concrete block, which displays an unusually thick layer of concrete dust or other loose and degraded material at the substrate surface. It is again emphasized that all salt crystals formed by the etching process must be removed prior to application of coatings.
For application of coatings systems over previously painted concrete surfaces, all signs of efflorescence and chalk-like deposits must be removed by a high-pressure water/detergent wash, followed by a thorough water rinse. After
affected surfaces are allowed to dry thoroughly, the appropriate coating system may be re-applied.
Finally, all new or previously painted surfaces must be free of dirt, grease, oils, excessive moisture, loose or crumbling materials and any other foreign matter prior to application of coatings. If there is any question as to the effective means of removing these materials from the concrete surface, contact a Columbia representative for specific recommendations.
|SSPC-SP-13, NACE 6
||This standard give requirements for surface preparation of concrete by mechanical, chemical, or thermal methods prior to the application of bonded protective coating or lining systems. The requirements of this
standard are applicable to all types of cementitious surfaces including cast-in-place concrete floors and walls, precast slabs, masonry walls, and shotcrete surfaces.|
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