Page 52 - Construction Waterproofing Handbook

2.16 CHAPTER TWO
The materials generally expand after being
wetted by the water contained in the concrete
mixture. This swelling action enables the
materials to fill the voids within the joint to
form a watertight construction joint. Since
these products expand in the presence of
water, they must not be wetted prematurely.
This requires that the second concrete place-
ment take place almost immediately after the
waterstop placement, otherwise the joint
might expand if exposed to rain or dew. The
asphalt plastic is not susceptible to moisture
like bentonite or hydrophilic materials, but
their limited elastomeric capabilities might
prevent the complete sealing of the joint if
some areas are not bonded properly.
The materials are easily installed in a variety
of positions for properly detailing watertight
joints below-grade as shown in Fig. 2.22. None
is meant for exposure to the elements and must
be completely covered by the concrete place-
ment. As such, they present limited expansion
capabilities for the substrate. When an expan-
sion waterstop material is required, the PVC or
rubber types are required.
Waterstop size is determined by the
expected head of water pressure to be
encountered at the joint. Table 2.2 summaries
the recommended waterstop and minimum
depth of embedment into the concrete sub-
strate for various head pressures. Actual site
conditions vary, and these measurements
should be used only as approximations.
Waterstop manufacturers will recommend
FIGURE 2.19 Placement of waterstop for first
half of concrete placement. (Courtesy of J.P. actual joint design when actual job conditions
Specialties, Inc.) are submitted for review.

WATERSTOP INSTALLATION

PVC/Neoprene Rubber/Thermoplastic Rubber
Waterstops of this type are placed in the concrete formwork and tied or secured to firmly
position the material during concrete placement. It is imperative that the waterstop is never
allowed to fold over during concrete placement. Figure 2.23 shows some typical methods
to secure the waterstop prior to the first concrete placement. Figure 2.24 details the method
for installing waterstop using a keyed joint.