Epoxy adhesive is a two-component adhesive based on an epoxy resin and a hardener that, by chemical reaction, cures to form a rock-hard, water- and chemical-resistant bond. Epoxy is one of the strongest adhesives in construction and is used wherever high loads, moisture or vibration are present.
How it works
Epoxy adhesive consists of two components:
- Part A — epoxy resin (liquid or paste)
- Part B — hardener or catalyst
After mixing in the correct ratio (often 1:1 or 2:1) the curing reaction begins. The adhesive cures by polymerisation, not by evaporation. As a result:
- Epoxy hardly shrinks while curing
- The bond is insensitive to moisture
- Epoxy reaches very high ultimate strength (up to 40 MPa tensile)
Types of epoxy adhesive
| Type | Cure time | Application |
|---|---|---|
| Fast | 5-10 minutes | Small repairs, putty |
| Standard | 30-60 minutes | Structural connections |
| Slow | 4-24 hours | Large surfaces, casting |
| Floor epoxy | 24 hours | Industrial seamless floors |
Applications in construction
- Chemical anchoring — threaded rods or bolts in concrete
- Structural bonding — steel to concrete, concrete to concrete
- Timber repair — restoration of structural beams
- Reinforcement bonding — carbon-fibre strengthening on concrete beams
- Resin floors — industrial, chemical-resistant floors
- Leak repair — even under water pressure
- Crack injection — filling cracks in concrete
Working procedure
- Clean — free of dust, grease, water
- Mix — exactly per specification, otherwise it will not cure
- Pot life — usually 5-30 minutes after mixing
- Apply — preferably to both surfaces
- Clamp — without movement during cure
- Final strength — usually after 24-72 hours
Pros and cons
Advantages:
- Very high strength (tensile, compressive and shear)
- Resistant to water, oils and many chemicals
- Fills gaps well (no perfect fit needed)
- Works on virtually all materials
Disadvantages:
- Expensive
- Limited pot life after mixing
- UV-sensitive (discolours outdoors)
- Not flexible — unsuitable for parts that flex strongly
Related terms
- Structural adhesive
- Chemical anchor
- Wood glue
- Polyurethane adhesive
- Sealant
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.