Control joints, also known as contraction joints, are cut into
new concrete to control cracking and to allow for expansion /
contraction. These joints are typically saw cut from 1/16"
to 1/4" wide. Heavy traffic over these joints will eventually
cause the edges to chip off. Joints left unprotected, and the
introduction on non-compressible materials (screws, nails, nuts,
bolts, pallet wood chips, etc.) in the joint will allow joint
edges to deteriorate causing major spalling. The best way to protect
joint edges is to fill them with a semi-rigid joint epoxy or polyurea
joint filler. These materials give adequate support to the joint
edges, have enough flexibility to withstand minor slab expansion
and contraction and are resilient enough to last the lifetime
of the floor. Epoxies and polyureas may also be used to fill in
construction joints and to fill random cracks once routed out
and cleaned.
NEW CONSTRUCTION
The best time to install an epoxy joint sealant is before the
floor is put into service. This will help prevent contamination
of the joint. For best results, allow the concrete to cure for
60-90 days and maintain the temperature of the facility at its
operating temperature for at least a week before the joint sealant
is installed. This will insure that the concrete has contracted
and the joint width has stabilized. At a minimum, the concrete
should be 28 days old. This is especially important in industrial
and commercial coolers and freezers.
REHABILITATION
If the floor has been in service for some time, any spalling
should be repaired using Fast Fix 10 or an epoxy mortar such as
Prime Bond 3100 Medium Mod mixed with an oven dried silica sand.
JOINT PREPARATION
Because semi-rigid joint sealants are designed to have relatively
low bond strength, proper surface preparation is very important.
Old joints should be recut using a dry cut saw such as Blastrac's
"Crac-Vac” that utilizes a vacuum system to minimize
airborne dust. To expose a clean, fresh, bonding surface the joint
should be cut a little wider than the original joint and 1"
deep ( ¾" deep minimum) just prior to installation.
Next, clean all of the dust out of the joint. Vacuum the joints
or use oil-free compressed air to clean residual dust from the
joints. Do not use a high-speed wire brush to abrade the joint
as this will glaze the concrete surface and close up the pores.
INSTALLING THE MATERIAL
Prime Seal epoxy and polyurea products should be preconditioned
to 65°-85° F (18°-29° C) before using. Cold epoxy
will set up a lot slower and will not flow as well. Pre-mix the
part "A" and "B" before batching the epoxy.
Refer to product data sheet or packaging for proper mix ratios.
Only mix the amount of material that can be used within the pot
life. Mix joint filler using a low speed drill with a mixing paddle
(never mix by hand). Scrape the sides and bottom of the pail while
mixing. Remember, large batches of epoxy will set up much faster
than smaller batches. (Note: In extreme cold environments, as
in floors in industrial refrigeration units, a polyurea product
should be used. Polyureas are not affected by the cold in the
ways epoxies are, and will set up in below freezing temperatures).
1/8" to1/4" of oven dried silica sand may be applied
to the bottom of the joint to prevent material from running through
shrinkage cracks at the bottom of the joint, but a minimum depth
of ¾" of epoxy / polyurea must be installed. Do not
use backer rod with epoxy / polyurea joint sealants unless the
joint is extremely wide and sand will not keep the material from
flowing out the bottom.
Material may be poured into the joint out of the mixing pail,
but it is best to use bulk load caulk guns, a two-component injection
pump, or Quick-Mix dual cartridges. Filling the joint from the
bottom up by injecting the material through a small nozzle will
help eliminate entrapped air pockets. Fill joints to full depth.
Shortly before the published pot life, the joints should be inspected
for low spots resulting from seepage. Top any low areas off with
neat material. Any over fills can be shaved flush with a razor
tool. There is no precise "ideal" time to shave the
material. We recommend trying in a small inconspicuous area to
get a feel for the material. Shaving is easiest on material that
has cured enough to no longer be flowable, yet still soft enough
to be "peeled" flush.
Prime Seal products are designed to crack or separate from sidewall
if too much slab movement is encountered. This is not a failure
of the material, but a safety feature. It prevents the concrete
from being pulled apart and cracking. If the joint separates,
the remaining seal will still offer some protection to the joint
sidewalls. Cleaning out the old material and refilling the void
with new material can repair a cracked or separated seal.
JOINTS OVER ½" WIDE
If the joints are over ½" wide, prime the sides of
the joints with neat joint fill material. Then mix 2-3 parts oven
dried aggregate (Prime Blend Sand) with the epoxy / ployurea.
The mortar can then be placed and trowel compacted into the joint.
The color of the epoxy mortar will generally be lighter than the
neat material. Excess material can be shaved or ground to make
flush.
RANDOM CRACKS
Random cracks in floors may be repaired using neat Prime Seal
5000, Prime Seal 5800 HD, or Fast Fix 10 (non moving cracks).
Route the cracks out to a depth of at least ¾" (one
inch is preferred). Clean the dust out of cracks and follow the
instructions for neat epoxy joint sealant.
VERTICAL JOINTS / SLOPED FLOORS / RAMPS
Vertical joints may be sealed using Prime Seal 5000 Caulk Grade.
The caulk grade offers all of the physical properties of the self-leveling
material, but with a thicker consistency. Prime Seal 5000 Caulk
Grade is available in bulk or our "Quick-Mix" cartridge
system.
FREEZER OR COOLER JOINTS
Temperatures in coolers or freezers tend to be constant. With
no temperature variation the concrete slabs will have little or
no movement. Semi-rigid or flexible materials are not a requirement
under these conditions.
Prime Seal 5700 or Prime Seal 5800 are ideal for use in industrial
freezers. The material will rapidly cure at temperatures as low
as -18° F (-28° C). Since these products are semi-rigid
materials, it is important that the room is conditioned to service
temperature prior to sealant installation.
Random cracks in industrial freezers may also be repaired using
Prime Seal 5700.
LIMITATIONS
Prime Seal 5000 should not be used for exterior applications.
Joint seal epoxy becomes rigid at temperatures below 40° F (5°
C) and will not maintain its bond as the concrete contracts.
In addition, sunlight causes epoxy to chalk and yellow. While this does not affect the performance of the material, it is usually not aesthetically pleasing.
