Pākiri Sand

Pākiri sand is amongst the highest quality sand available in New Zealand, making it ideal to produce the concrete our construction sector needs.

Sand is an essential component for making concrete, which is produced from a mix of cement, sand, aggregates and water. Since it was first used in ancient Rome, it has become an essential component in the growth and development of economies worldwide.

Sand is used in concrete production to fill the voids between the aggregates used. This minimises the requirement for cement while maintaining the dimensional stability required to produce good quality concrete.

Over time, the demand for quality sand has increased as Auckland has grown and as building standards have evolved, requiring strength improvements in concrete to ensure longevity and safety. This has driven increasing demand for high-quality Pākiri sand.

Marine sands, such as those found in the Mangawhai-Pākiri embayment, are ideal for making concrete.

Marine sands, such as those found in the Mangawhai-Pākiri embayment, are ideal for making concrete. They have a high quartz feldspar content with no minerals that promote alkali silica reaction.

In terms of shape, marine sands are sub rounded to sub angular, which helps provide strength in concrete. The particle size is also ideal for making concrete.

Pākiri sand allows a reduction in the cement required to produce strong concrete, which helps lower the carbon dioxide emissions produced per cubic metre of concrete produced.

The sand at Pākiri also does not contain any of the volcanic alkali reactive minerals present in other sands found in most deposits of the upper North Island. The reactions between these minerals and highly alkaline cement, particularly in high strength concrete, can reduce the life of the structures constructed.

Geologically, Pākiri sand is thought to have originated from the ancestral Waikato River, which once flowed east into the Hauraki Gulf at a time when sea levels were much lower.

This ancient river deposited an enormous amount of sand off the coast of Pākiri, with estimates the Mangawhai-Pākiri embayment holds between 1.7 and 3 billion cubic metres of sand.

On top of this large base, sand continues to enter the embayment from several sources.

Erosion from streams and headlands, creation of shell fragments from biogenic production, and the ongoing flow of sand from both deeper water and around the headlands means sand extracted is replenished. For this reason, the embayment has been categorised as only a partially closed system.

With this plentiful supply, high quality Pākiri sand is in demand for infrastructural and industrial purposes. So much so, that manufacturers of concrete as far away as the Bay of Plenty and Napier use Pākiri sand as a proportion of the mix when they produce infrastructure concrete.

Pākiri sand is classed as a nationally significant resource. It has been used in some of the country’s most important and high-profile infrastructure projects – including the Sky Tower, Waterview Tunnel, Newmarket Viaduct and the Auckland Harbour Bridge. Both the City Rail Link and Central Interceptor are currently being supplied ready mix and pre-cast concrete from multiple concrete suppliers using Pākiri sand.