If the floor has been in service for some time, any spalled areas should be repaired using Fast Fix 10 or an epoxy mortar such as Prime Bond 3100 Medium Mod. Joints being repaired should be filled with a polyurea such as Prime Seal 5700 GP (general purpose) or Prime Seal 5800 HD (heavy duty). Polyureas are relatively new polyurethane hybrids. Polyureas have many of the same attributes of epoxy (tough and durable). However, in some situations, polyureas have a marked advantage over epoxies. For example, polyureas will cure in below freezing situations, and will cure much faster than epoxies. Fast cure times are critical in busy industrial settings where plant shut-down is not an option.

Polyureas also have good expansion properties and bond to concrete with as much strength and adhesion as epoxy sealants. Some epoxy manufacturers claim that polyureas and epoxies bond differently, with epoxy sealants “leap-frogging” or “scissor kicking” from one side of a joint wall to the other, while polyureas separate from only one side of a joint. However, our extensive laboratory tests indicate that polyureas also bond from side to side when installed properly. The lab photos below show Prime Seal 5800 HD, a polyurea sealant, at break during a bond test run per the Georgia DOT test method # GDT 58. This type of break pattern occurred in all samples that were tested:

Prime Seal products are actually designed to crack or separate from the 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. A cracked or separated seal can be repaired by cleaning out the old material and refilling the void with new material. When comparing products between manufactures, look closely at laboratory test results. Any reputable manufacturer should be able to provide testing to back up their marketing claims.

Our studies indicate that adhesion should not be a comparative concern when choosing a polyurea over an epoxy. What is more important in joint rehab, is the ability to provide a quick turn-around and to get the area operational as soon as possible. Because polyureas set up much faster than epoxies (usually within minutes) they are an ideal choice for rehab and repair projects where areas being shut down cost the owner time and money.

Polyureas are not recommended for new construction due to the moisture present in new slabs. Bleed water and moisture in the concrete can cause a polyurea material to bubble or froth. It is also important that older concrete be clean and dry during polyurea sealant installation to insure a successful rehab project.

A flush repaired joint can be achieved, using a polyurea sealant. Ideally, polyureas should be slightly overfilled in the joint then shaved flush prior to fully curing. One can quickly determine the ideal time to shave by playing with small samples of the polyurea to learn its properties. Because of their dense, strong compressive properties (which can be substantially higher than epoxy sealants), polyureas can sometimes be tricky to shave flush if they are not shaved prior to fully curing. Some contractors circumvent this problem easily enough by applying a small amount of fine sand to the surface of the sealant during initial cure. This sand sprinkled on top will more easily facilitate grinding after curing.

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 epoxies 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). Polyureas, unlike epoxy sealants, are not temperature sensitive. They will cure in sub-zero temperatures with their properties intact. Since these products are rigid materials, it is important that the room be conditioned to service temperature prior to sealant installation.

Random cracks in industrial freezers may also be repaired using Prime Seal 5700.