Here are the basic steps for successful low-pressure crack injection. Keep in mind, however, that the type of epoxy used and the time required for injection will vary with each job depending on the crack width, wall thickness, and other conditions. These can also be bought as crack repair kits that some with all the tools and supplies needed for the project.
Install injection ports: Surface Ports (short rigid-plastic tubes with a flat base) serve as handy entryways for getting the repair material into the crack. They eliminate the need to drill into the concrete, reducing labor time and cleanup. The base of the port is placed directly over the crack and bonded to the surface with an epoxy paste. A general rule-of-thumb is to space the ports an inch apart for each inch of wall thickness.
Mounting the Ports & capping the crack: Use an epoxy adhesive (such as Miraclebond 1450 Epoxy Paste) to seal over the surface ports and exposed cracks. The paste cures in about 20 to 45 minutes to provide a surface seal with excellent bond characteristics that holds up under injection pressures. The entire exposed crack is covered with the paste, leaving only the port holes uncovered.
Using the correct injection epoxy: For cracks where both sides can be sealed, consider the injection epoxy to be used on the width of the crack you will be injecting. ATC Epoxy such as Miraclebond 1450 Epoxy Paste is typically used for wide crack repairs, and Crackbond LR-321 Gel is typically used for medium sized cracks, or blindside cracks. For fine and hairline cracks the Crackbond SLV-302 Penetrating Epoxy and the Crackbond LR-321 Injection Resin should be used.
Injecting the crack: Begin injecting at the lowest port on the wall and continue until the epoxy begins to flow out of the port above it. That’s the visual sign that the crack has been filled to that level. Plug the first port with the cap provided and move up to the next port, repeating this procedure until the entire crack has been filled with epoxy. Let the compression spring on the dispensing tool push the material into the crack using slow, constant pressure. This will reduce the possibility of leaks or blow-outs and allow time for the repair material to fully penetrate the crack.
Remove the ports: Allow 24 to 48 hours at room temperature for the epoxy to cure and penetrate into the cracks. The injection ports can then be removed by striking them with a trowel or hammer. If appearance is an issue, the epoxy surface seal can be chipped away, sanded off with a Kraft Rub Brick, or ground off with a sanding disk. Another option is to use a surface seal that can simply be peeled off the wall after the repair is fully cured. All of the crack injection supplies are available in the ATC Epoxy Crack Repair Kits.