Page 313 - Construction Waterproofing Handbook

EXPANSION JOINTS 6.17
Preformed rubber systems
There are numerous preformed rubber systems available. These are manufactured from
extruded synthetic rubbers such as neoprene and hypalon. They are available in countless
cross sections and sizes. Unlike the bellows systems, they require a blockout or ledge in
the substrate on which to place joint material. Many systems require an epoxy or poly-
meric concrete nosing at joint edges to prevent damage.
Many preformed systems have flanges attached to a compression seal that is perforated
to allow for embedding into nosing material for mechanical bonding of joints to substrates.
Other systems use metal frames for attachment to concrete substrates before concrete
placement. Still others rely on chemical bonding to a substrate with adhesives.
1
Preformed rubber systems are available in widths ranging from 4 to 6 in. Movement capa-
bility varies, but it is usually 50 percent compression and expansion movement. Rubber sys-
tems are very resistant to weathering and chemical attack from gasoline, oils, and grease.
These systems are typically used for straight horizontal runs only, but some are
designed for use at vertical-to-horizontal junctures. These joints do not allow for 90°
changes in plane. Some of the numerous cross sections of preformed expansion joints are
shown in Fig. 6.15.
2
Preformed systems have high impact (tensile) strength, usually more than 1000 lb/in .
This strength reduces movement capability,
and materials should be sized accordingly.
The high tensile strength allows for excel-
lent wear resistance on areas subject to
large amounts of vehicular traffic.
Preformed systems do have limitations on
the amount of shear and deflection move-
ment they are able to withstand.
Only one portion of a preformed joint,
the nosing, is job-site-manufactured. This
nosing anchors a joint to a substrate. Size of
the nosing and adhesive contact area must
be installed properly to ensure that the joint
does not rip from the substrate during
weathering or movement (Fig. 6.16).
Mechanical attachment of preformed
systems is completed by using metal
anchor bolts installed through holes in the
rubber flange joint section (Fig. 6.17).
These systems require a blockout to allow a
joint to be flush with a substrate. Anchoring
should be checked by maintenance crews
on a regular basis, since bolts may work
themselves loose during joint movement.
Horizontal seams are sealed by mitering
ends of the rubber portion and fusing them
FIGURE 6.15 Preformed rubber expansion joints. with a solvent.