Polished Concrete
Design tip: Polished concrete delivers LEED v4 points for energy (high thermal mass) and materials (no additional finish layer), making it a favourite for modern sustainable interiors.
Quick Definition
Polished concrete is not a topping. It is the original floor slab refined by progressive grinding with diamond abrasives, hardened with a lithium-silicate densifier, and polished to a matte, satin, or mirror sheen.
Glossary Snapshot
| Attribute | Range / Value | Notes |
|---|---|---|
| Gloss Level | 1 (matte) – 4 (high-gloss) | Per ICRI 310.2R |
| Surface Hardness | > 8 Mohs (post-densification) | Depends on cement paste quality |
| Slip Resistance | 0.50–0.70 DCOF (dry) | Add micro-texture where wet conditions |
| Typical Lifespan | 20–30 yr with routine burnishing | No topical sealer to delaminate |
| VOC Emissions | Zero—process is mechanical | Ensure densifier is water-borne |
Good to know: Unlike epoxy or terrazzo, polished concrete breathes, allowing vapour transmission—ideal for on-grade slabs in humid climates.
Installation Workflow
- Evaluation & Mock-up – Test grind to confirm aggregate exposure and finish level.
- Initial Grind – 40–80 grit metal-bond diamonds remove laitance, high spots, and coatings.
- Densifier Application – Lithium or sodium silicate penetrates, reacts with free lime, and hardens the paste.
- Progressive Honing – 100 → 200 → 400 grit metal/resin diamonds refine scratches.
- Polishing – 800 → 1 500 → 3 000 grit resin diamonds develop desired sheen.
- Guard (optional) – Micro-film stain-guard burnished into surface.
- Maintenance Plan – Neutral-pH cleaner + periodic high-speed burnish.
Aggregate Exposure Classes
| Class | Description | Visual Result |
|---|---|---|
| Cream | No coarse aggregate exposed | Uniform, variegated cement paste |
| Salt & Pepper | 0–3 mm aggregate visible | Fine speckled appearance |
| Medium | 3–10 mm aggregate visible | Terrazzo-like mottling |
| Large | 10+ mm stone fully exposed | Bold, decorative stone look |
Selecting the exposure class early avoids costly re-grinds once cabinetry and partitions are installed.
Performance Benefits
- Low Lifecycle Cost – No wax; simple auto-scrub extends life.
- High Reflectivity – Up to 30 % light bounce; potential lighting-energy savings.
- Thermal Mass – Moderates indoor temperature swings.
- No Peeling Risk – Unlike topical epoxy, there’s nothing to delaminate.
- Allergen-Free – Seamless surface resists dust mites & mould.
Limitations
- Substrate Quality Matters – Cracks, spalls, and patchwork will remain visible.
- Noise & Vibration – Grinding generates 85-90 dB; schedule after-hours.
- Moisture Migrate – Can telegraph salts (efflorescence) if slab lacks vapour barrier.
Sustainability Angle
- Material Efficiency: Uses the existing slab—zero additional finish layer.
- Low Chemicals: Water-based densifiers (< 50 g/L VOC).
- Long Service Life: Outlasts vinyl or carpet by 3×, reducing replacement waste.
FAQs
How is polished concrete different from a clear sealer on concrete?
A sealer is film-forming and subject to scratching/peeling; polishing is within the concrete and cannot delaminate.
Can I polish an old slab with oil stains?
Yes, but the stains may ghost. Degrease, apply poultice, or splice in repair mortar before grinding.
Does polished concrete need to be re-sealed?
No full re-seal; maintenance is periodic burnishing and re-applying guard every 2–3 years in high-traffic zones.
Related Terms
References
- ICRI 310.2R-2013 Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, Polymer Overlays, and Concrete Repair.
- ACI 310R-13 Guide to Decorative Concrete.
- ASTM E430-21 Standard Test Methods for Measurement of Gloss of High-Gloss Surfaces.