Epoxy injection is a specialized concrete crack repair technique that uses low-viscosity epoxy resin to fill and structurally bond cracks in concrete. When properly executed, it can restore the tensile and shear strength across a crack to levels approaching that of the original concrete. But it is not appropriate for all cracks — using epoxy injection in the wrong situation can make a problem worse. Here is what you need to know.
How Epoxy Injection Works
The epoxy injection process begins with preparing the crack — cleaning it of dust, debris, and moisture that could interfere with epoxy adhesion. Entry ports (small injection nipples) are installed along the length of the crack at intervals matched to the crack width and depth. A surface seal of epoxy paste is applied along the crack face between ports to prevent epoxy from escaping during injection.
Low-viscosity epoxy resin (two-component, mixed at the nozzle) is then injected at low pressure through each port, beginning at the lowest port and continuing upward as epoxy appears at the next port. The epoxy fills the crack completely, and once cured (typically 24–72 hours depending on temperature and formulation), it bonds the two sides of the crack into a monolithic unit. For structural concrete, the cured epoxy typically exceeds the tensile strength of the surrounding concrete.
When Epoxy Injection Is Appropriate
Epoxy injection is appropriate for dormant structural cracks — those that are no longer moving — in concrete that is otherwise sound and dry. It is commonly used on parkade beams and columns with flexural cracks, building walls and foundations with settlement cracks that have stabilized, and post-tension slab cracks that have been assessed and confirmed stable. The crack must be free of significant contamination and ideally dry, as most epoxy systems do not adhere well to wet concrete.
It is not appropriate for active cracks that are still moving due to thermal cycling, ongoing settlement, or structural distress. Injecting a rigid material into a moving crack will result in re-cracking adjacent to the injection. Polyurethane foam or flexible polyurethane grout injection is a better choice for active water-bearing cracks. Our concrete repair services include both epoxy and polyurethane injection, selected based on crack assessment.
Limitations and Alternatives
Epoxy injection does not address the cause of the crack — only the symptom. If the crack was caused by ongoing settlement, freeze-thaw cycling, or structural overloading, injection alone will not prevent recurrence. A complete assessment of crack origin is necessary before selecting a repair method.
For cracks in parkade decks that are water-bearing, routing and sealing with polyurethane sealant is typically more appropriate than epoxy injection, as the sealant remains flexible and accommodates the movement that would re-crack a rigid fill. See our parkade waterproofing services for crack sealing as part of a comprehensive deck restoration, and check our FAQ for more on crack repair options.
Contact Miyagi Construction for a free site assessment at estimate@miyagiconstruction.com or call (778) 513-7471.
Additional Resources
For more information on concrete standards and construction safety in British Columbia, visit CSA Group and the WorkSafeBC for industry standards and guidelines.
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