Field Notes: Fixing floor cracks with polyurea

Field Notes: We stopped in to observe Floor Consultants doing floor repair of a big box retail warehouse facility south of the Atlanta airport. They are repairing spalls, cracks, voids and joint nosings (the edges of concrete slabs). It’s a pleasure watching true masters of their craft in action. They are using a combination of Prime Resins products to address different repairs: Prime Flex 985 LX10 for slab stabilization and void fill, Joint Shield 5500 Polyurea 95A for crack and joint repair, and Prime Bond 3000 Fast epoxy mixed with sand to fix spalls and joint nosings and patch holes.

Industrial concrete floors that see a lot of traffic are prone to spalls and cracks over time. If not repaired promptly and correctly, those seemingly minor flaws can lead to major damage to surrounding concrete and to unlevel floors. Uneven floors lead to undue wear and tear on forklift equipment and operators, possibly leading to injury and repairs.

Example of improperly installed polyurea joint fill: too shallow and V-cut.

This illustrates what not to do in floor joint filling: Too shallow of a cut and a V-cut rather than vertical cut made it easy to pull this polyurea joint filler out of a joint.

We recommend filling cracks and joint with Joint Shield 5500 Polyurea 95A, a semi-rigid joint filler. As important as the right product is the right installation procedure. For step-by-step directions, go here to download our Prime Practice procedure for using polyurea joint filler. We recommend a 1-inch vertical saw cut of the area to be filled. That cut should be cleaned free of dust and debris prior to filling to ensure a proper bond to the concrete. Some contractors use a V-cut rather than a vertical cut. No big deal, right? Wrong! What happens, as you can see from this photo, is that material is not deep enough in the concrete and can squeeze back out of the crack or joint. Regular thermal expansion and contraction will create movement in the joint. Material in a vertical joint will get clamped between the slabs while material in a wedge-shaped V-cut can get squeezed out during expansion. In this example, the original contractor not only used a V-cut, he also did not cut nearly deep enough, resulting in a strip that was easy to pull from the floor.

Here you can see a good example of before and after of a properly saw-cut crack and one that has been filled with polyurea joint filler. Using the right product and the right technique, these repairs will last many years, adding life to the facility and minimizing damage to equipment and injury to workers.

crack in concrete floor that has been sawcut in preparation for polyurea joint filler

A properly prepared crack ready to be filled with polyurea joint filler.


A crack that has been filled with Joint Shield 5500 Polyurea 95A.

2 Responses to “Field Notes: Fixing floor cracks with polyurea”

  1. Mike Zacharias says:

    I want to buy some Prime flex 920 cartridge s

    • Prime Resins says:

      Thanks for your interest, Mike. I emailed you directly so that we can put you in touch with the appropriate rep or dealer.

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