The Case For Concrete Roads

The Case for Concrete Roads report says concrete roads are on average 17 per cent cheaper over whole-of-life, reduce embodied carbon in roading and significantly reduce the cost and frequency of road maintenance.

The report by consultancy Infometrics, commissioned by Concrete New Zealand, builds on reports from 2013, 2018 and 2020, to present a compelling case for the use of concrete in roading.

“The report looked at roading costs in New Zealand and considered extensive research overseas,” Infometrics Chief Forecaster Gareth Kiernan says.

“The report shows that although concrete roads cost more to build, savings can amount to millions of dollars for central government and councils as maintenance costs are up to 62% lower. Lifetime carbon emissions for concrete roads may also be better than tarseal because concrete reabsorbs carbon dioxide.”

Kiernan says lack of capability has been a major limitation for concrete roading in New Zealand.

“The Government could play a role to overcome this hurdle, for example by funding a pilot project. Expanding the industry’s capability to be able to build concrete roads, with their extra resilience, could also be increasingly important as heavier electric vehicles become more common.”

Noting that approximately one in two highways in the US are built using concrete, Concrete New Zealand chief executive Rob Gaimster says concrete roads should complement existing roading typologies.

“Concrete roads are best used in applications where there are high traffic densities and areas of high stresses from heavy vehicles. We can see a number of stretches of road where concrete would save money and time, such as Auckland’s Port Motorway, the Cambridge section of the Waikato Expressway to the intersection of SH1 and SH29 at Piarere and SH1, North of Levin.”

He says the report showed concrete roads could have a lower carbon footprint over whole-of-life than asphalt if carbon uptake is taken into account. Carbon uptake is a natural process by which exposed surfaces of hardened concrete absorb atmospheric CO2 over time.

Emissions associated with concrete roads can be even further reduced by using low carbon concrete. In addition, concrete can be recycled.

National Road Carriers Association CEO Justin Tighe-Umbers says concrete roading for limited projects is a no-brainer in New Zealand.

“The whole-of-life economics present a compelling case for this durable, low-maintenance solution. It should be considered for the new Roads of National Significance and Roads of Regional Significance to provide a lower total cost of ownership.

“On top of that, concrete roads are rigid and therefore can reduce fuel consumption and, as our summers grow hotter, concrete roads don’t melt. While concrete will not suit every roading purpose, it certainly deserves more consideration than has occurred to date in New Zealand.”

Hamilton Mayor Paula Southgate says her city is the fastest growing in New Zealand and it must look at new and innovative approaches to deliver the infrastructure it needs.

“Innovation, quality work and better cost efficiency are important principles in all construction projects we do in Hamilton city.

“We recently trialled Roller Compacted Concrete (RCC) on Arthur Porter Drive, a busy industrial road with unique construction challenges. The early results are promising, and shows us that concrete is a smart and sustainable choice for future projects, though of course each new project will need to be assessed individually.”

The 2024 report summarises selected international comparisons of concrete and asphalt roading costs. The consensus is that concrete roads are almost always more cost-effective than asphalt roads over a life of 40 years. Cost variations in different countries arise due to differing labour and other input costs, the type of asphalt or concrete technology, the discount rate used when calculating costs over whole of life, and the differing life span of roads.

Infometrics drew on this data, and available New Zealand data, to run 20,000 computer simulations of roading construction and maintenance costs in New Zealand. The result is a 12% to 23% advantage in costs to concrete over asphalt for the central 90% of the distribution of results. The weighted mean is a 17% cost advantage to concrete.

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