Concrete injection is a specialized repair technique in which cracks, voids, or honeycombing in concrete are filled by injecting a liquid material — typically epoxy resin, polyurethane resin, or cement grout — under controlled pressure. The injected material fills the crack from the inside, bonds the concrete surfaces back together, and restores structural integrity or watertightness.
Types of Injection Materials
Different materials serve different purposes:
- Epoxy resin injection: Creates a bond that is often stronger than the surrounding concrete. Used for structural crack repair where load transfer across the crack must be restored. Rigid once cured.
- Polyurethane resin injection: Expands on contact with moisture and cures into a flexible or semi-flexible seal. Ideal for stopping water leaks in basements, tunnels, and tanks. Not typically used for structural repair.
- Cement grout injection: A Portland cement-based slurry used for filling larger voids, honeycombing, and wider cracks. Lower cost but less precise than resin methods.
How the Process Works
- The crack is cleaned and surface-sealed between injection points using a fast-setting paste.
- Injection ports (small nozzles) are installed at regular intervals along the crack.
- The chosen material is pumped in under low to moderate pressure, starting at the lowest port and working upward (for vertical cracks) or from one end to the other (for horizontal cracks).
- Once material appears at the next port, that port becomes the new injection point.
- After curing, the ports and surface seal are removed or ground flush.
Application
Concrete injection is used on cracked foundations, basement walls, retaining walls, parking decks, water tanks, and bridge structures. For homeowners, it is most commonly encountered when repairing leaking basement walls or cracked foundation beams. While small-scale DIY injection kits exist, structural crack repair should always be assessed by a qualified engineer to determine the cause of cracking before treatment.
Related terms
- Concrete damage
- Crack
- Foundation
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