Epoxy
Design tip: Because epoxy terrazzo can accept any pigment, it’s perfect for corporate brand colours or striking super-white floors that cementitious binders can’t achieve.
Quick Definition
Epoxy is a synthetic polymer formed by mixing an epoxy resin (Part A) with
a polyamine hardener (Part B).
The ensuing exothermic reaction creates a densely cross-linked plastic noted
for its bond strength, chemical resistance, and glossy finish.
Typical Formulations
| Component | % by Weight | Function | Notes |
|---|---|---|---|
| Bis-A or Bis-F Epoxy Resin | 60 – 80 % | Primary polymer backbone | Bis-F offers lower viscosity |
| Polyamine Hardener | 10 – 30 % | Cross-linking agent | Accelerators vary cure time |
| Pigments / Fillers | 0 – 10 % | Colour, rheology control | Titanium dioxide for bright whites |
| Additives (defoamer, UV inhibitor) | < 5 % | Improve appearance & durability | UV blockers minimise yellowing |
Good to know: Epoxy is inherently UV-sensitive; clear coats may amber outdoors. For exteriors, use aliphatic polyurethane or polyaspartic topcoats.
Key Properties
- Compressive Strength: 70–100 MPa (10,000–14,500 psi)
- Bond Strength to Concrete: ≥ 2.5 MPa pull-off (ASTM D4541)
- Water Absorption: < 0.5 % by weight (24 h)
- Chemical Resistance: Excellent against oils, solvents, weak acids
- Working Time: 20–45 min @ 21 °C (70 °F) depending on formulation
Popular Interior Applications
-
Thin-set Terrazzo (6–10 mm)
Creates seamless, high-colour floors with divider strip patterns. -
Epoxy Floor Coating (0.5–2 mm)
Dust-proofs concrete, adds chemical & abrasion protection—ideal for commercial kitchens, labs, garages. -
Self-Levelling Underlayment
Levels uneven slabs before installing luxury vinyl, tile, or hardwood. -
Adhesive / Anchor
Bonds countertop slabs, re-bars, or structural timber connections.
Installation Workflow (Floor Coating)
- Surface prep – Shot-blast or diamond-grind to CSP 3 – 4, < 5 % moisture.
- Prime coat – Low-viscosity epoxy seals pores, promotes adhesion.
- Body coat – 100 % solids epoxy squeegeed & back-rolled; add chips/quartz.
- Intermediate grind (optional) – Knock down high spots.
- Topcoat – Clear or pigmented epoxy/urethane for UV & wear resistance.
- Cure – Light foot traffic in 12 h; full chemical cure in 5–7 d.
Sustainability Considerations
- VOC Content: 100 % solids systems can be zero-VOC; avoid solvent-cut epoxies where possible.
- Longevity: 20-year life cycle often offsets higher embodied carbon compared with vinyl tile that needs replacement every 5–7 years.
- Bio-based Resins: Emerging soy- or castor-oil epoxies reduce reliance on petroleum feedstocks by up to 35 %.
FAQs
Why does epoxy yellow in sunlight?
Aromatic epoxy chains absorb UV, breaking polymer bonds and causing amber discolouration. Overcoat with aliphatic polyurethane or include UV blockers to mitigate.
Can I install epoxy over green concrete?
Yes—use a moisture-tolerant primer if slab RH ≤ 95 % (ASTM F2170). Otherwise wait 28 days or add a vapour-mitigation membrane.
How is epoxy different from polyurethane?
Epoxy excels in adhesion & chemical resistance; polyurethane offers superior UV stability and scratch flexibility. Many commercial floors use an epoxy build coat with a polyurethane topcoat for hybrid performance.
Related Terms
References
- ASTM D638-22 : Standard Test Method for Tensile Properties of Plastics.
- ACI 548.4R-14 : Guide for Epoxy-Based Bonding Systems for Concrete.
- SSPC-PA 7 : Application of Thin Film Epoxy Floor Systems.