Concrete Tip of the Day #9: Getting Decorative – Coloured and Exposed Concrete Done Right

Decorative concrete has come a long way from the basic grey slab. With today's technology, we can offer an impressive palette of coloured and exposed concrete finishes to suit every aesthetic. But with greater customisation comes the need for greater care—from planning and placement to managing customer expectations.

Setting Expectations Early

Coloured concrete is under more scrutiny than standard mixes because it’s a deliberate, premium choice. Customers expect perfection, but colour variation is natural. Even with consistent pigments, factors such as raw material colour, placement method, weather conditions, and curing all influence the final appearance. It’s essential to communicate that colour samples won’t perfectly match what’s poured on-site.

Planning is Everything

Start with a well-prepared, dampened sub-base—consider using a DPC under driveways for moisture control. Plan joint layouts carefully and ensure everyone involved (from the placer to the supplier) knows their responsibilities. Avoid small final loads to prevent inconsistent pigment dosing.

Compaction, Timing & Voids

Exposed concrete requires excellent compaction. Blowholes and surface voids are common if the mix sits too long or is placed too slowly. While admixtures can extend workability beyond 90 minutes, delays still pose a risk.

Natural contaminants like driftwood or seasonal lupin seed are inherent risks with river-sourced aggregates. Though they’re not usually problematic on exposed surfaces, they may show through on coloured concrete if not managed.

Environmental Considerations

Exposing concrete generates highly eco-toxic slurry. Runoff must not reach stormwater systems. Use products like READY Gel or manage disposal off-site. Acid washing carries similar risks—ground soakage is only viable with good soil drainage.

What to Expect with Surface Effects

• Colour variations can arise from trowel marks, different water content, sun shadows, and substrate inconsistency (causing the “Pinto effect”).

• Efflorescence (a white surface mask) is natural and more visible in dark colours. Use sealers like READY Sealer to minimise this.

• Blemishes such as air voids, aggregate streaks, or cracking often appear after exposing the top layer. These are usually due to poor vibration, late screeding, or uneven surface prep.

• Inconsistent exposure can result from paste-rich zones or low points in the surface.

Seal and Protect

We strongly recommend sealing all decorative surfaces. Follow the sealer supplier's instructions carefully. Different products perform differently, and incorrect application can lead to dissatisfaction.

Managing Client Expectations

If a perfectly uniform surface is expected, concrete might not be the right choice. Talk openly about possible variation, cracking, and surface blemishes. Explain the benefits of sealers and the importance of long-term maintenance. And always assess the finish from a 3-metre distance, as per the visual assessment standard (AS 3114).

Conclusion:Coloured and exposed concrete offers incredible design opportunities. With the right planning, placement, and communication, the results can be stunning and enduring. Take the time to manage expectations—and the surface will speak for itself.

✅ Stay tuned for the next episode of Concrete Tip of the Day!