Page 351 - Construction Waterproofing Handbook

REMEDIAL WATERPROOFING 8.11
damage. Soaking will also deepen penetration of salts and other contamination into pores
of a substrate, which follow-up pressure washing may not remove.
Available water supplies often contain minerals that stain or streak existing substrates.
Water purification equipment is necessary to treat water before application.
Surfaces being prepared for waterproofing applications by using water soaking require a
long drying period. As long as 1 month may be necessary for substrates to dry sufficiently.
Also, to prevent damage, preliminary remedial waterproofing, such as tuck-pointing, will be
required before start of soaking.
Steam cleaning, although used extensively in the past, is now almost obsolete due to
expanding technology in pressure-cleaning equipment. Steam equipment rapidly heats
water in a self-contained boiler; then it spray-applies water under low pressure. The heated
water swells and loosens collected pollutants, enabling them to be rinsed off a substrate.
Results achieved by steam cleaning are now reachable by pressure equipment that is
much lower in cost than steam equipment. However, particular substrates can be so cont-
aminated that too high a pressure may be required to achieve results obtained by steam
cleaning. (See Table 8.1.)

Abrasive cleaning
Abrasive cleaning uses an abrasive material to remove mechanically accumulated dirt and
pollutants (Fig. 8.9). Abrasive cleaning methods include:
● Sandblasting
● Wet aggregate blasting
● Sanding belts
● Wheel grinders
Abrasive cleaning systems remove not only surface accumulations of dirt but also some
portion or layer of a substrate itself. This surface damage is often severe, and substrate
restoration may be necessary. These systems are not preferred for substrate preparation,
waterproofing applications, or general building cleaning, and are not acceptable to most
restoration and preservation professionals.
Abrasive cleaning is now typically limited to paint removal on metal substrates,
although this procedure is now economically possible with advanced technology in water-
blasting equipment and chemical paint removers.
Wet aggregate cleaning is the mildest abrasive cleaning process. This method uses a
vortex attachment on a pressure cleaner that suctions sand to mix with water at the spray

TABLE 8.1 Water-Cleaning Properties
Advantages Disadvantages
Several methods available, including pressure Introduces water to envelope components
and soaking
Chemicals can be added if required Improper cleaning can damage substrate or cause
streaking
Variable pressures Environmentally safe