Page 149 - Construction Waterproofing Handbook

3.38 CHAPTER THREE
● Modified urethane
● Sheet systems

Acrylics
Acrylics are not waterproof coatings, but act as water-repellent sealers. Their use is pri-
marily aesthetic, to cover surface defects and cracking in decks. These coatings have low
elastomeric capabilities; silica aggregate is premixed directly into their formulations,
which further lowers their elastic properties. These two characteristics prevent acrylics
from being true waterproof coatings.
The inherent properties of acrylics protect areas such as walkways or balconies with no
occupied areas beneath from water and chloride penetration. In addition to concrete sub-
strates, acrylics are used over wood or metal substrates, provided that recommended
primers are installed. Acrylics are also used at slab-on-grade areas where urethane coat-
ings are not recommended.
Sand added in acrylic deck coatings provides excellent antislip finishes. As such, they
are used around pools or areas subject to wet conditions that require protection against
slips and falls. Acrylics are not recommended for areas subject to vehicular traffic. Some
manufacturers allow their use over asphaltic pavement subject only to foot traffic, for aes-
thetics and a skid-resistant finish. (See Table 3.14.)

Cementitious
Cementitious deck coatings are used for applications over concrete substrates and include
an abrasive aggregate for exposure to traffic. These materials are supplied in prepacked
and premixed formulations requiring only water for mixing. Cementitious coatings are
applied by trowel, spray, or squeegee, the latter being a self-leveling method.
Cementitious systems contain proprietary chemicals to provide necessary bonding and
waterproofing characteristics. These are applied to a thickness of approximately 8 in and
1
will fill minor voids in a substrate. A disadvantage of cementitious coatings, like below-
grade cementitious systems, is their inability to withstand substrate movement or cracking.
They are one-step applications, with integral wearing surfaces, which require no primers
and are applicable over damp concrete surfaces.
Modified acrylic cementitious coatings are also available. Such systems typically
include a reinforcing mesh embedded into the first coat to improve crack-bridging capa-
bilities. Acrylics are added to the basic cement and sand mixture to improve bonding and
performance characteristics.
Cementitious membrane applications include the dry-shake and power-trowel methods pre-
viously discussed in Chap. 2. Successful applications depend on properly designed, detailed,

TABLE 3.14 Acrylic Deck-Coating Properties

Advantages Disadvantages
Ease of application Not a complete waterproof system
Aggregate is integral with coating No movement capability
Slab-on-grade applications Not resistant to vehicular traffic