Rapid Flex CJ 
Rapid curing, semi-rigid polyurea control joint filler
Rapid Flex CJ is a top-grade, 100% solids, two-component, UV-resistant, semi-rigid, rapid-curing polyurea solution designed for filling control and construction joints in industrial concrete floors. Its formulation allows for quick shaving of joints, facilitating fast project turnaround. Developed to meet the ACI 302, section 4.10 recommendations for joint fillers, Rapid Flex CJ features a Shore A Durometer of 85. It’s also effective for repairing damaged joint nosing and cracks, with additional architectural colors available for diverse project needs.
- Simple 1:1 mixing ratio with a pourable and pumpable consistency
- UV-resistant and maintains color integrity (Dovetail Gray when mixed)
- High elongation rate (200%) minimizes tearing from movement
- Provides semi-rigid flexibility without welding slabs together or aging into brittleness
- Ideal hardness (Shore A = 85) supports wheel load transfer and allows moderate movement
- Applicable and cures in temperatures as low as -20°F
- Faster setting and curing times than traditional epoxy fillers, leading to quicker project completion
Application
Surface Preparation
- Joint Cleaning: Ensure joints are clean, dry, and free of curing compounds, densifiers, sealers, or any other foreign substances. Use a vacuum-equipped dry-cut abrasive blade and oil-free compressed air to remove water or dust before application.
- Joint Depth: Install Rapid Flex CJ full depth in sawcut control joints and at least 2 inches deep in joints greater than 2 inches. Avoid using compressible backer rod in sawcut control joints. In construction joints, dry sand or backer rod can be used to reduce volume while maintaining a minimum 2-inch depth.
Mixing and Application
- Mixing Instructions: Ensure Rapid Flex CJ components are at least 50°F for mixing. Stir or shake each component before dispensing. Use a 1:1 ratio, low-pressure duplex/plural component metered pump with a 3/8” x 24” static mixer.
- Application Process: For cartridge or plural component pump applications, dispense mixed material into a waste container first to ensure uniform color and consistent 1:1 ratio. Then, dispense properly mixed Rapid Flex CJ into the prepared joint. Overfill joints and allow to cure for about 1 hour, up to 24 hours before shaving flush with the floor using a razor scraper.
- Curing and Shaving: Rapid Flex CJ sets quickly, reducing the risk of staining joint sides. If installed before maximum concrete shrinkage, a crack may appear, which can be refilled with Rapid Flex CJ after cleaning with SpecChem Solvent 100.
Packaging
Available in 22 fl oz cartridges and 10-gallon units.
Shelf Life
Rapid Flex CJ should be stored in its original containers, kept tightly closed between 55-90°F, ensuring a shelf life of one year from the date of manufacture.
Standards
- Approved for use in USDA, FDA, and CFIA regulated environments
- Complies with ACI 302 guidelines for “Floor Joint Filler”
- 100% solid content, VOC-free, and LEED compliant
Documents
Rapid Flex CJ Specification
Control Joint Filler Detail
Rapid Flex Colorant System Flyer 2025