By Rob Gaimster, Chief Executive, Concrete NZ

Damage wrought by cyclone Gabrielle and Auckland’s floods demonstrate the twin imperative for climate change adaptation and mitigation.

Concrete does and will continue to play an important role in enabling Aotearoa New Zealand to adapt to the impacts of climate change – particularly extreme weather events.

The response to our urgent need for resilient infrastructure, whether that be flood defences, stormwater management, electricity supply (wind, hydro‑electric and geothermal) or roading networks, will inevitably have a concrete foundation.

Concrete roads

During the first part of 2023, the condition of the country’s roads was a topic of great debate as a plague of potholes caused much grief. The situation was exacerbated when periods of hot weather saw asphalt surfaces literally come unstuck.

Prime Minister Chris Hipkins has indicated that one solution will be to relocate stretches of vulnerable roads to more stable ground. While rerouting roads makes sense in terms of building a more resilient transport network, the materials they are built with must also be resilient.

The level of maintenance work required of our asphalt road network is enormous. This situation has been made more challenging by the recent closure of the Marsden Point Oil Refinery and subsequent questions around the bitumen supply chain. The inherent durability of concrete roads would lessen this burden – a priority as the impact of climate change will make extreme weather events more frequent.

Concerns around access to buried services, skid resistance, surface noise and the seismic resilience of concrete roads can all be addressed through appropriate design, as demonstrated overseas.

The economics of concrete roads have been proven time and time again, with Infometrics having demonstrated that, in a preferred scenario, concrete is around 30 per cent less expensive than its asphalt counterpart.

The final tick in the plus column is for the sustainability credentials of concrete, including low carbon attributes and industry commitment to decarbonise.

This is where concrete’s part in climate change mitigation comes into play.

Recent achievements

The New Zealand concrete industry has already made big strides towards the collective goal of net zero carbon by 2050.

In 2020, independent sustainability consultancy thinkstep-anz found that the industry is well placed to meet the climate change commitments that the government signed up to under the Paris Agreement.

thinkstep-anz has confirmed that emissions from concrete production decreased by 11 per cent between 2005 and 2020. This occurred against an 11 per cent increase in demand and was achieved through a range of measures, including the use of waste products such as wood biomass to fuel cement kilns.

Decarbonisation road map

In the second half of this year, Concrete NZ will publish a road map to net zero carbon by 2050 for the New Zealand concrete industry. By describing an achievable pathway to producing net zero concrete by 2050, the decarbonisation road map will set out a positive vision for how the industry can play a major role in building a sustainable future.

The road map will include the levers (and milestones) needed to achieve net zero carbon concrete by the middle of the century.

Examples of these levers are the progressive substitution of coal with alternative fuels in cement manufacture, the uptake of fly ash and ground granulated blast furnace slag as cement replacements, and accounting for the absorption of carbon dioxide from the atmosphere by concrete during its service life and following recycling.

It will cover both ready-mixed concrete and concrete products, and also involves the major participants in the concrete value chain, including cement manufacturers, concrete producers, and designers of buildings and infrastructure.

Developed with support from thinkstep-anz and engagement with Concrete NZ’s member groups, the road map is also informed by, and aligned with, international work, such as the Global Cement & Concrete Association’s 2050 Cement and Concrete Industry Roadmap for Net Zero Concrete.

Building on past and current initiatives, the concrete industry will look to remain successful in reducing its emissions by leveraging further research and development, investment, and commitment from researchers, government, and all stakeholders across the value chain.

Low-carbon initiatives

This point regarding the road map’s ongoing relevance is exemplified by strong decarbonisation progress during the first half of 2023, in the form of low-carbon concrete capability initiatives from New Zealand suppliers.

Holcim New Zealand has opened a new low-carbon cement replacement facility adjacent to the company’s existing cement import terminal at Ports of Auckland. At peak operation, the site should enable replacement of just under 100,000 tonnes of Portland cement, which will substantially reduce greenhouse gas emissions. In fact, emissions savings are expected to reach more than 75,000 tonnes a year – roughly equivalent to 3600 flights from Auckland to Christchurch, or removing 34,700 cars from the roads.

At the same time, New Zealand’s largest concrete producer, Fletcher Building, has announced a contract to increase its use of waste ash from Huntly Power Station to produce lower-carbon concrete.

This circular solution for pond ash is in addition to the significant annual amount of fly ash that Golden Bay is already diverting from landfill, helping them to lower the carbon of the concrete they produce.

It also adds to Golden Bay’s decision to access end-of-life tyres and wood waste as alternative fuels in its cement production process near Whangārei.

Additionally, Fletcher Building has opened a Concrete Innovation Lab in Christchurch, which is dedicated to fast-tracking the development of new concrete products with a focus on decarbonising concrete to support construction needs and specifications changes in response to the need to build for climate change.

The road ahead

The concrete industry’s road to decarbonisation, combined with the inherent resilience of the world’s most widely used construction material itself, has hugely positive implications for New Zealand’s future infrastructure.

As we consider the resilience of the built environment in the wake of months of extreme weather, the emergence of low-carbon concretes based on the industry’s net zero carbon commitment provides opportunities to build with materials that assist with both the mitigation of, and adaptation to, climate change.