How does crack injection work?

Epoxy resins inject cracks into walls that have an opening of 0.5 mm or more than that, since the epoxy resins used in the injection of the cracks cause the ends of the crack to bond together to prevent leakage. Even if a crack isn't leaking now, water will eventually find it, says Lou Cole, president of Emecole Inc.

How does crack injection work?

Epoxy resins inject cracks into walls that have an opening of 0.5 mm or more than that, since the epoxy resins used in the injection of the cracks cause the ends of the crack to bond together to prevent leakage. Even if a crack isn't leaking now, water will eventually find it, says Lou Cole, president of Emecole Inc. Cole says that in the Midwest, crack injection has been an accepted way of approaching these repairs for many years, and more and more foundation repair contractors across the country are adopting the technique because it is cost-effective, reliable, and permanent. Epoxy injections are designed and used to restore the strength and integrity of structural elements in cracked concrete.

But these cracks must be relatively dry for the epoxy to achieve adhesion. After all, epoxy injections will not shift or react with water. Therefore, they are ineffective for waterproofing a leaky crack. This type of injection is done from inside your basement, thus avoiding the need to excavate your foundations.

Injection is a low-pressure injection (less than 450 psi) of epoxy resin through injection ports installed along the crack. These ports are attached to the wall by using an epoxy anchoring paste. This paste is applied over the entire length of the crack of the base and, together with the outer floor, serves as a barrier to confine the epoxy within the crack of the base so that the injected epoxy is contained over the entire length of the crack. Epoxy injection is typically performed on dry substrates compared to polyurethane injection, which works very well on wet and actively leaking substrates.

Epoxy injection is the preferred method when structural crack repair is desired. For many years, engineers have been looking for ways to fully inject repair polymers into cracked concrete structures. The general consensus is to seal the crack with a sacrificial epoxy and install injection ports every few centimeters. Thick epoxy is then injected at high pressure into the crack with expensive resin injection pumps.

The process takes a long time, the epoxy is brittle, the equipment is expensive, and the skill level is highly specialized. This makes epoxy injection slow, costly and not really effective in the field. The application that seemed to show the greatest promise for its dual cartridge system was the low-pressure injection of cracks in concrete. All injection products have the disadvantage of being somewhat unpredictable because both hole drilling and material injection are done blindly.

Epoxy crack injections are typically performed at lower injection pressures (20-200 psi) and with surface mounted ports. Because these repairs are inconvenient and often costly, your best crack repair strategy is to focus on prevention and control. The use of low pressure for injection is of concern to some people who might think that the resin will not fully penetrate the base wall if the pressure is too low. Either way, the repair of concrete cracks in the foundation or slab can be completed efficiently and effectively in as little as an hour or more.

Air-operated tools are also available for dual cartridge dispensing and allow injection pressure control. Because epoxy and polyurethane foams used for crack injection are two-component materials, it is critical to mix them in the correct proportions to avoid problems with unreacted polymers. As stated above, epoxy crack injection is not as versatile as polyurethane crack injection; therefore, not all cracks can be properly injected with epoxy resin. The expansive and forceful nature of polyurethane, as well as its increased reactivity in the presence of moisture and its flexibility once cured, make it the resin of choice for most repairs of leaking foundation cracks.

In situations where the crack penetrates completely through the concrete element and the rear part of the concrete element cannot be sealed (e.g. If water seeps continuously through the crack, the flow must be stopped for the epoxy injection to produce a proper repair. Quite simply, epoxy injection resin is essentially a glue that, once cured, has a bonding strength that exceeds the strength of concrete; this makes epoxy ideal for repairing structural cracks. Polyurethane injection foam is mainly a water-activated sealant or a leak-sealing grout with expansion properties during reaction.

To fill a typical crack in a residential foundation wall, injecting at pressures above 40 psi may not be effective. . .

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