Page 181 - Masonry and Concrete

Masonry Construction Techniques
180 CHAPTER FIVE

acid cleaners because metals react with acid, leaving marks on the
wall that can oxidize and leave stains. Muriatic acid can also discolor
pigmented mortars, so it should be pretested and used with caution on
this type of work. Cleaning should be scheduled as late as possible in
the construction.
Walls should be cleaned when they are in the shade rather than in
the sun so that the cleaning solutions do not dry out too quickly. Con-
fine cleaning to small areas that can be rinsed before they dry. For
cleaning new masonry, the Brick Industry Association (BIA) has estab-
lished guidelines for the selection of methods depending on the type
of brick used (Figure 5-34).

5.8.3 Cleaning Fresh Mortar Smears

On brick and other clay masonry units, the mortar must be thoroughly
set and cured before it can be properly removed. Trying to clean wet
mortar from the surface presses the cement paste into the unit pores,
making it harder to clean. Wooden paddles or nonmetallic scrapers
should be used to remove large mortar droppings. For small splatters,
stains, or the residue from larger pieces, a medium-soft fiber-bristle
brush is usually adequate. Any motions that rub or press mortar parti-
cles into the unit face should be avoided. Mortar that cures too long is
harder and more difficult to remove than fresh splatters, and may
require acid cleaning. Mild acid solutions easily dissolve thin layers of
mortar. Large splatters should be scraped off first and, if necessary, the
residue removed with acid. Muriatic acid is suitable for cleaning clay
masonry if it is diluted in a ratio of one part acid to nine parts water.
Muriatic acid should never be used on light-colored tan, buff, gray, or
pink brick because it can react with minerals in the clay and cause
green vanadium or brown manganese stains.
Mud, dirt, and soil can usually be washed away with a mild deter-
1
gent solution consisting of 2 cup dry measure of trisodium phosphate
1
(TSP) and 2 cup dry measure of laundry detergent to one gallon of
clean water. Dried mud may require the use of pressurized water or a
proprietary “restoration” type cleaner containing hydrofluoric acid and
phosphoric acid. Hydrofluoric acid, however, etches polished surfaces
such as glass, so adjacent windows must be protected from accidental
contact. Hydrofluoric acid is not suitable for cleaning mortar stains and
splatters because it cannot dissolve portland cement products.

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