Crack Injection: A Comprehensive Guide

Cracks in walls can lead to water leakage and structural damage. Learn how epoxy resins can be injected into cracks with an opening of 0.5 mm or more to prevent leakage.

Crack Injection: A Comprehensive Guide

Cracks in walls can be a major cause of concern for homeowners, as they can lead to water leakage and structural damage. Fortunately, there is a reliable and cost-effective solution to this problem: crack injection. Epoxy resins are injected into cracks with an opening of 0.5 mm or more, which causes the ends of the crack to bond together and prevent leakage. According to Lou Cole, president of Emecole Inc., crack injection has been an accepted way of approaching these repairs in the Midwest for many years, and more and more foundation repair contractors across the country are adopting the technique.

Epoxy injections are designed to restore the strength and integrity of structural elements in cracked concrete. However, for the epoxy to achieve adhesion, the cracks must be relatively dry. 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 also preferred when structural crack repair is desired.

Engineers have been looking for ways to fully inject repair polymers into cracked concrete structures for many years. 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.

Air-operated tools are also available for dual cartridge dispensing and allow injection pressure control. Because both hole drilling and material injection are done blindly, all injection products have the disadvantage of being somewhat unpredictable. To fill a typical crack in a residential foundation wall, injecting at pressures above 40 psi may not be effective. Epoxy and polyurethane foams used for crack injection are two-component materials; therefore, 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. 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. 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), it must be stopped for epoxy injection to produce a proper repair. 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; however, this type of repair can be completed efficiently and effectively in as little as an hour or more.

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