Black Oxide Exposed Aggregate Concrete Patio – Mt Eden Auckland

Exposed aggregate concrete patio curing under tarpaulin with control joints at internal corner Mt Eden Auckland

We recently completed a premium concrete patio pour in Mt Eden, Auckland, installing a black oxide exposed Longburn pebble finish. This type of decorative concrete patio delivers a high-end look, but achieving a long-lasting result relies heavily on correct preparation, reinforcement, and curing.

Concrete Preparation & Base Work

The success of any concrete slab starts well before the pour. For this project, we ensured:

  • A well-compacted, level sub-base
  • Properly chaired reinforcing mesh
  • Adequate reinforcing steel throughout

This provides the strength and stability required for a durable concrete patio and helps minimise long-term movement.

Reinforcement for Crack Prevention

To reduce the risk of cracking, we installed additional reinforcing in high-stress areas. This included reinforcing bars placed diagonally at internal corners and around slab penetrations, which are common weak points in any concrete pour.

These measures help distribute stress and significantly lower the chance of visible cracking in the finished slab.

Control Joints & Saw Cutting

Proper control joint placement is essential for any concrete patio installation. Prior to pouring, we mapped out all joints, spacing them evenly at no more than 3 metres and positioning them in high-risk locations such as internal corners.

All concrete saw cuts were completed approximately 24 hours after the pour. This ensures any natural shrinkage occurs within these planned joints rather than randomly across the slab.

Concrete Curing Process

Curing is one of the most critical stages of a concrete pour and has a major impact on strength and crack prevention.

On completely flat slabs, ponding (submerging the slab in water) is often the most effective curing method, as it keeps the surface consistently saturated.

However, for exterior concrete slabs like this patio — which are designed with fall to shed water — ponding isn’t practical. Instead, we:

  • Wet the slab thoroughly
  • Covered it with vapour barrier and tarpaulins
  • Maintained moisture by running hoses underneath the coverings twice daily

This approach slows down moisture loss and helps the concrete cure evenly. If fresh concrete dries too quickly before reaching sufficient strength (MPa), the risk of shrinkage cracking increases significantly.

There are also alternative curing methods available, including spray-applied curing compounds and specialised curing blankets, both designed to retain moisture and improve curing performance.

Exposed Aggregate Finishing

This patio features a black oxide exposed aggregate finish using Longburn pebble, creating a durable, textured surface.

While the initial pour is complete, we will return in approximately one month to carry out an acid wash. This process further exposes the aggregate, enhances the contrast, and brings out the full visual detail of the finish.

If your interested in the different types of decorative concrete finishes you can find them here on our suppliers website Decorative Concrete

Concrete Contractors Mt Eden Auckland

This project highlights the importance of proper concrete preparation, reinforcement, joint placement, and curing techniques when installing high-quality decorative concrete patios.

If you’re looking for experienced concrete contractors in Mt Eden or across Auckland for patios, driveways, or landscaping works, get in touch with our team. Click here to see one of our other landscaping project in Remuera, Kwila deck stairs & aluminium fencing.

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