Page 65 - Construction Waterproofing Handbook

BELOW-GRADE WATERPROOFING 2.29
substrates need not be dry for application. Chemical systems do not require curing, but
capillary systems do.

Acrylic modified systems
Acrylic modified cementitious systems add acrylic emulsions to a basic cement-and-
sand mixture. These acrylics add waterproofing characteristics and properties to in-place
materials. Acrylic systems are applied in two trowel applications, with a reinforcing
mesh added into the first layer immediately upon application. This mesh adds some
crack-bridging capabilities to acrylic installations. However, since the systems bond
tenaciously to concrete or masonry substrates, movement capability is limited.
Acrylic cementitious systems are applicable with both positive and negative installations.
Concrete substrates can be damp, but must be cured for acrylic materials to bond properly.
Alkaline substrates can deter performance of acrylic-modified cementitious systems.
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Acrylic-modified materials are applied in a total thickness of approximately 8 in.
Reinforcing mesh eliminates the need for protective covering of the systems on floor areas
in minimal or light-traffic interior areas.
The properties of all types of cementitious systems are summarized in Table 2.4.

CEMENTITIOUS SYSTEM APPLICATION

Before applying cementitious systems, substrates must be free of dirt, laitance, form
release agents, and other foreign materials. Manufacturers typically require concrete sur-
faces to be acid-etched, lightly sand-blasted, or bush-hammered to a depth of cut of
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approximately 16 in. This ensures adequate bonding to a substrate.
All tie holes, honeycomb, and cracks must be filled by packing them with an initial
application of the cementitious system. Refer to Fig. 2.37. Construction joints, wall-to-floor
joints, wall-to-wall intersections, and other changes in plane should be formed or grooved
with a 1-in by 1-in cutout to form a cove. This cove is then packed with cementitious mate-
rial before initial application. This is a critical detail for cementitious systems, as they do
not allow for structural or thermal movement. This cove prevents water infiltration at weak
points in a structure where cracks typically develop. At minimum, if a cove is not formed,
place a cant of material at the intersections, using a dry mix of cementitious material.
Cementitious systems do not require priming of a substrate before application.
However, wetting of the concrete with water is necessary.
Cementitious systems are available in a wide range of packaging. They may be pre-
mixed with sand and cement in pails, or chemicals and iron may be provided in separate

TABLE 2.4 Properties of Cementitious Waterproofing Systems

Advantages Disadvantages
Positive or negative applications No movement capability
Remedial applications Job-site mixing required
No subslabs or well pointing required Not for high traffic areas