Control joints, also known as contraction joints, are cut into new concrete to allow the concrete to expand and contract without cracking. These joints are typically 1/16" to ½" wide.
Heavy traffic over these joints will cause the edges to chip off. If left unprotected, the joints will continue to deteriorate causing major spalling. The best way to protect the joint edges is to fill them with a semi-rigid epoxy joint sealant such as Prime Seal 5000 Semi-Rigid. This material was designed to give adequate support to the joint edges, have enough flexibility to withstand minor slab expansion and contraction (82% tensile elongation), and be resilient enough to last the lifetime of the floor. Prime Seal 5000 Semi-Rigid may also be used to fill in construction joints.
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.
REHABILITATION
If the floor has been in service for some time, any spalled areas should be repaired using an epoxy mortar such as Prime Bond 3100 Medium Mod.
JOINT PREPARATION
Because semi-rigid joint sealants have a relatively low bond strength, proper surface preparation is very important.
Old joints should be recut using a dry cut saw. We recommend Saw Tec’s "Crac-Vac" that includes a vacuum system to minimize airborn dust. The "Crac-Vac" is available through Prime Resins. The joint should be cut a little wider than the original joint and at least ¾" deep. Best results are obtained if the cut is one to two inches deep.
New and recut joints should then be abraded. Use a dry cut abrasive blade on both sides of the joint.
Next, clean all of the dust out of the joint. Vacuum the joints or use oil-free compressed air to blow the joints clean.
Do not use a high speed wire brush to abrade the joint. This will glaze the concrete and close up the pores.
INSTALLING THE MATERIAL
Prime Seal 5000 should be preconditioned to 65° -85° F (19° -30° C) before using. Cold material will set up a lot slower and will not flow as well. Pre-mix the part "A" and "B" before batching the epoxy. Measure exactly 1 part "A" to 1 part "B" by volume into a clean pail. Only mix the amount of material that can be used within the pot life. Mix epoxy for three minutes using a low speed drill with a mixing paddle (never mix by hand). Scrape the sides and bottom of the pail while mixing. Large batches of epoxy will set up much faster than small batches.
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 must be installed. Do not use backer rod with epoxy 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, squeeze bottles, or a two component injection pump. 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.
Within 30 minutes the filled joints should be inspected for low spots resulting from seepage. Top these areas off with neat material.
Prime Seal 5000 is 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 Prime Seal 5000 separates, the remaining seal will still offer some protection to the joint side walls. A cracked or separated seal can be repaired by cleaning out the old material and refilling the void with new Prime Seal 5000.
JOINTS OVER ½" WIDE
If the joints are over ½" wide, prime the sides of the joints with neat Prime Seal 5000. Then mix 2-3 parts oven dried aggregate (Prime Blend Sand) with the epoxy. The mortar can then be poured and trowel compacted into the joint. The color of the epoxy mortar will generally be lighter than the neat material.
RANDOM CRACKS
Random cracks in the pavement may be repaired using neat Prime Seal 5000. 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.
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 5000 Freezer Flow was designed for industrial freezers. The material will rapidly cure at temperatures as low as -18° F (-28° C). Since Prime Seal 5000 Freezer Flow is a rigid material, 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 5000 Freezer Flow.
LIMITATIONS
Prime Seal products 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.
