Leveraging aggregate resources for infrastructure

Two-thirds of aggregate rocks extracted from quarries or river gravels are used for roading

The New Zealand infrastructure industry is currently undergoing both policy and structural reforms, and its direction will be governed by a new entity called the New Zealand Infrastructure Commission, Te Waihanga.

It represents a step-change in New Zealand’s approach to infrastructure and is on track to be operational before the end of the year. The efficient planning, delivery and maintenance of the right infrastructure is essential to improving New Zealand’s economic performance and our wellbeing.

Regional Economic Development Minister Shane Jones has said: “The single most common complaint I hear when I travel around the country – particularly in the regions – is about the quality of basic infrastructure. We need quality advice about long-term infrastructure planning to ensure we’re making the best investment decisions for the entire country.”

Tackling the systemic problems

The Infrastructure Commission will be mandated to develop a long-term infrastructure strategy by working with central and local government, as well as the private sector, with a view to tackling the systemic problems the sector has been facing for many years.

The commission will have two broad functions – strategy and planning, and procurement and delivery support. It will provide expert advice, planning and strategy, and support the delivery of major infrastructure projects across the country. It will also be a one-stop shop for investors, including publishing a pipeline of infrastructure projects.

As an autonomous Crown entity with an independent board, the commission will have the credibility and influence required to effect real change. Ministers will retain final decision-making rights, as is appropriate.

Aggregate and the research project overview

Aggregate (unbound or bound crushed and processed mineral rock) forms the basic building material by volume of all longitudinal land transport and most vertical building infrastructure. The government will be investing about $42 billion through to 2022 in net capital spending in infrastructure, with the majority requiring various specifications of aggregate material. With this level of investment, we need to take a longer-term view and make decisions that align with our priorities to build a productive, sustainable and inclusive economy, and improve the wellbeing of all New Zealanders.

In March of this year, the University of Auckland completed a four-year research project funded by the Ministry of Business, Innovation and Employment (MBIE) examining the integrity of aggregates that are used on New Zealand roads. Infrastructure durability and improved environmental outcomes require appropriate asset lifecycle management that depends upon improved aggregate decision-making across factors that include demand, supply, processing, design and specification, construction, asset management, operation, renewal and recycling and reuse techniques.

The project director Dr Doug Wilson, Emeritus Professor Philippa Black and researcher Ms Chris Webster presented the project findings at five separate workshops during February and March of this year.

The first workshop was held at Waitangi where the post-governance settlement entities (PGSEs) [the tribes that have completed their treaty settlement negotiations with the Crown] gather at Waitangi for the annual Iwi Chairs Forum prior to celebrating Waitangi Day. The team also held workshops in Whangarei, Hamilton, Auckland and Wellington.

Unlocking economic potential

Prior to attending Waitangi, Prime Minister Jacinda Ardern and Minister Shane Jones announced a $100 million investment to unlock the economic potential of whenua Maori and to drive regional growth in Northland.

PM Jacinda Ardern: “Access to capital remains a challenge for Maori landowners as the special status of their land means commercial banks are less willing to lend to them. I’m pleased that through the Provincial Growth Fund (PGF), we’re in a unique position to be able to support these landowners. Funding will enable Maori to access the capital required to progress projects which are investment-ready and will ultimately support moves towards higher-value land use.”

Research released in 2013 found about 80% of Maori freehold land was under-utilised or unproductive. Modelling of the impact of bringing this land into primary sector production and increasing its productivity shows significant economic benefits, including jobs. As both custodians and investors, Maori have a large and growing asset base across regional New Zealand based on traditional land holdings and treaty settlements.

Minister Shane Jones: “Supporting Maori economic development is a key focus of the PGF. That is because lifting the productivity of Maori land will have enormous benefits for regional economies and it is an opportunity we cannot afford to ignore.”

The government is promoting land development, part of which may attract Maori landowners to consider investment n the aggregates industry and potentially receive funding from the PGF for capital projects.

The Leveraging Aggregates Project 2015–2019

Two-thirds of aggregate rocks extracted from quarries or river gravels are used for roading. There is an abundant supply of aggregate, but the supply of appropriate quality aggregate in the correct location, with the right properties and undergoing the appropriate treatment, is key to the effective construction and maintenance of transportation and associated vertical infrastructure.

The cost of transporting aggregates on roads is substantial: within the first 30 km of travel, the transport cost for each tonne of aggregate produced approximately doubles.

In addition, a significant proportion of the commodity tonnage on state highways in New Zealand is moving aggregate resources, which, due to their bulk density, causes significant deterioration of the road pavements. Yet in some regions, local good-quality aggregate supply sites and production quantities are diminishing as city boundaries expand. These regional planning practices can compromise the supply of aggregate, significantly raising the cost of infrastructure.

In 2010, the regulations covering the length and weight of high-productivity motor vehicles (HPMVs) were modified.
This change allowed longer and heavier vehicles on some roads in New Zealand.

Together, these factors are driving the need to better utilise appropriate local materials closer to the source, with improvement techniques that could potentially also include sourcing aggregate from Maori land.

Specific and appropriate engagement is required with treaty settlement entities and Maori landowners which take a long-term relational view, recognising that Maori landowners have a strong connection to whenua and that there are historical grievances related specifically to public agencies that in some cases have still not been adequately addressed.

Research project outcomes

Aggregate materials, once sourced and consented to, require cost-effective extraction and processing and, potentially, improvements so that they are fit for purpose

This research has developed guidelines for good engagement practices with Treaty settlement entities and Maori landowners.

The materials, once sourced and consented to, require cost-effective extraction and processing and, potentially, improvements so that they are fit for purpose.

The research has also undertaken investigations of the source properties and production processes of different aggregates, and has related these properties to their durability and engineering performance – e.g. effective lifetime, need for maintenance, and road safety outcomes.

Further, the research has also developed new technologies to improve aggregate testing and durability. The intention is to enable the aggregates industry to reduce aggregate transport costs, reduce road maintenance and construction costs, improve road safety, reduce wastage and improve the performance of pavements.

Key outcomes from the research are:

  • The development of case studies to determine the demand for aggregate for roading purposes and an initial econometric study
  • Consideration and description of aggregate supply factors
  • Better understanding of key factors that make an aggregate ‘marginal’ and the reasons for non-compliance
  • Identifying industry practices and procedures that hinder use of local materials or recycled materials closer to source/ demand
  • The development of new methods and techniques to predict an aggregate’s surface properties to improve road safety management
  • An improved understanding of how aggregates (greywacke and andesites) weather over relatively short time periods of exposure to wet and drying cycles
  • Development of a guide to assist industry to engage with Maori landowners in the aggregate extractive industries.

About the project and the team

The project, led by Dr Doug Wilson and Emeritus Professor Philippa Black at the University of Auckland, involved a team of eight multi-disciplinary specialists from engineering, geology, resource and land-use planning and economics.

The research programme involved collaboration with New Zealand and overseas experts. The project has strong links with the New Zealand aggregates industry and research has been undertaken on a collaborative basis with various central and local government departments, aggregate member organisations, the Iwi Chairs Forum, Maori landowners and private industry companies.


Dr Doug Wilson is the director of the transportation engineering laboratories in the Department of Civil and Environmental Engineering at the University of Auckland; he has over 15 years’ consulting experience whilst working for private engineering consultants, local and central government engineering agencies, and over 20 years’ lecturing experience at the University of Auckland and prior organisations.

Emeritus Professor Philippa Black specialises in mineralogy and metamorphic petrology and headed the Department of Geology at the University of Auckland for 15 years; between 1993 and 1997 she was president of the Royal Society of New Zealand – the first woman to hold the role.

Chris Webster is a social scientist specialising in land-use planning, and holds a postgraduate Diploma in Engineering Management from the University of Auckland; for almost 15 years she has worked in the infrastructure industry, contributing her combined field experience, government policy and treaty settlement knowledge.