What Is an Epoxy Crack Filler?
An epoxy crack filler is a two-component reactive resin system designed to fill, seal, or structurally repair cracks in concrete. Unlike polyurethane or acrylic crack fillers that remain somewhat flexible, epoxy crack fillers cure to a rigid, high-strength solid that restores the structural continuity of the concrete.
We manufacture three distinct types of epoxy crack filling products, each designed for specific crack widths and repair objectives.
Three Types of Epoxy Crack Filler
1. Injection Resin (XQ-LF-L / XQ-LF-M)
For structural crack repair where the goal is to restore load transfer across the crack. Low viscosity (XQ-LF-L): 150-300 mPa·s — penetrates cracks as narrow as 0.1mm. Cured tensile strength exceeds 40 MPa, making the repaired crack stronger than the surrounding concrete. Medium viscosity (XQ-LF-M): 1,000-2,000 mPa·s — designed for wider cracks (0.3-5mm) where the low-viscosity resin would flow through and out the other side. Higher gap-filling ability with 35 MPa tensile strength. Application: Pressure injection at 0.2-0.4 MPa through ports bonded along the crack line.2. Surface Seal Paste (XQ-LF-SS)
A thixotropic epoxy paste applied to the concrete surface to seal crack openings before injection or to seal non-structural surface cracks. Purpose: During crack injection, the surface seal prevents injected resin from leaking out through the crack opening. It can also be used alone to seal dormant surface cracks that do not require structural repair. Application: Trowel or spatula application to a width of 20-30mm centered on the crack line. Cure time is 4-6 hours before injection can begin.3. Concrete Floor Crack Sealer (XQ-LF-FC)
A self-leveling low-viscosity epoxy specifically formulated for horizontal crack repair in floors, slabs, and pavements. Key feature: Self-leveling — simply pour along the crack and the resin flows into the opening by gravity, filling it from bottom to top. No injection equipment needed. Application: Clean the crack, apply masking tape along both sides (to control spread), pour resin along the crack, allow gravity fill, remove tape after initial cure, and sand flush.When to Use Each Type
| Scenario | Product | Method |
|---|---|---|
| Structural crack in beam or column | XQ-LF-L or XQ-LF-M | Pressure injection |
| Crack in basement wall (water seepage) | XQ-LF-L (if dormant) | Pressure injection |
| Floor slab crack | XQ-LF-FC | Gravity pour |
| Surface seal before injection | XQ-LF-SS | Trowel application |
| Hairline crack, aesthetic only | XQ-LF-SS | Surface application |
| Active crack (still moving) | XQ-LF-PU (polyurethane) | Pressure injection |
Performance After Repair
A properly executed epoxy crack injection creates a repair that is structurally superior to the original concrete. Our low-viscosity injection resin (XQ-LF-L) achieves a tensile strength greater than 40 MPa after cure, while typical concrete has a tensile strength of only 2-4 MPa.
In pull-off bond tests, the failure occurs in the concrete substrate, not at the epoxy-concrete interface or within the epoxy itself. This confirms that the repaired section is at least as strong as the uncracked concrete.
However, this performance is only achieved with proper crack preparation and injection technique. Contaminated cracks (oil, grease, organic growth), improperly sealed cracks (resin leakage during injection), or incomplete filling (air pockets, insufficient injection pressure) will all reduce the effectiveness of the repair.
Shelf Life and Storage
All our epoxy crack filling products have a 12-month shelf life when stored in original sealed packaging at 5-25°C. Store away from direct sunlight and heat sources. Once opened, components should be used within 6 months.
The products are supplied in dual-cartridge systems (injection resins) or pre-measured kits (floor sealer, surface seal paste) to ensure correct mixing ratios in the field.
Frequently Asked Questions
What is the best epoxy crack filler for concrete?
The best epoxy crack filler depends on crack width. For structural cracks 0.1 to 1.0 mm wide, low-viscosity injection resin (100 to 500 mPa·s) is the best choice because it penetrates deep into fine cracks and cures to tensile strength exceeding 40 MPa. For wider cracks 1.0 to 5.0 mm, medium-viscosity resin (1,000 to 3,000 mPa·s) prevents excessive flow-through. For surface cracks that do not require structural repair, an epoxy surface seal paste applied by trowel is the most practical option.
Can epoxy crack filler be used on wet concrete?
Standard epoxy crack fillers require a dry substrate for optimal bonding. If the crack has active moisture, you should first inject polyurethane foam to stop the water infiltration, then follow with epoxy injection once the surface is dry. Our XQ-LF-PU polyurethane sealant is designed specifically for wet-crack applications and expands on contact with water to form a watertight seal.
How long does epoxy crack filler take to cure?
Cure time varies by formulation and temperature. At 25 degrees Celsius, our injection resins reach handling strength in 6 to 8 hours and full cure in 7 days. Surface seal paste cures faster — typically 4 to 6 hours to touch-dry and 24 hours to full strength. At lower temperatures (10 degrees Celsius), cure times approximately double. Below 5 degrees Celsius, use a heated enclosure or choose a rapid-cure formulation.
What is the difference between crack injection epoxy and crack filler paste?
Crack injection epoxy is a low-viscosity liquid (100 to 3,000 mPa·s) designed to be pumped or gravity-fed into cracks to fill them completely from within. It provides structural repair by bonding the crack faces together. Crack filler paste is a thick, trowel-applied material used to seal surface cracks or fill spalls from the outside. Paste does not penetrate deeply and is primarily cosmetic or waterproofing, not structural. For cracks affecting load-bearing capacity, injection is always the correct method.
How much does epoxy crack filler cost per meter of crack?
Material cost for epoxy crack injection typically ranges from $5 to $15 per linear meter of crack, depending on crack width, depth, and member thickness. A 0.3 mm wide crack in a 200 mm thick wall uses approximately 60 mL of resin per linear meter. Surface seal paste costs $2 to $5 per linear meter. These are material costs only — labor for professional injection adds $15 to $40 per linear meter depending on access difficulty and project location.
View our complete crack repair range or request a quote for your project.