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NZ Construction News (Feb / Mar 10) A Concrete Opportunity to Pave a Significant Road Forward

01 Mar 2010

A Concrete Opportunity to Pave a Significant Road Forward

Rob Gaimster – Cement & Concrete Association of New Zealand (CCANZ)

In 2009 the government announced a considerable investment programme in seven of New Zealand’s main transport routes. Dubbed the Roads of National Significance (RoNS) the routes have been presented as critical to providing infrastructure access to important markets and areas of employment and economic growth.

Centred on New Zealand's five largest population centres, which are struggling under heavy traffic volumes and roads that require upgrading to reduce congestion and improve safety, the New Zealand Transport Agency (NZTA) believe the RoNS represent a substantial change in planning for major national transport infrastructure in New Zealand.

Unlike transport network improvements in the past, which have tended to be reactive and focused on enhancements to keep pace with growth, the RoNS have been advanced by the NZTA as lead infrastructure - proactive improvements that encourage economic growth.

There is little doubt that the RoNS, as part of the current Government’s overall commitment to infrastructure expenditure, are appropriately ambitious and aligned with the objectives of promoting and securing long-term prosperity. It is therefore timely to examine how alternative roading materials, such as concrete, can assist to maximise this watershed period in New Zealand’s roading network development.

Concrete’s durability offers any investment in our roading network significant potential returns. A concrete road’s extended service life, low maintenance and reduced fuel consumption benefits are all well documented and compelling economic factors for the adoption of concrete roads within the RoNS.

A recent CCANZ commissioned study, which presented an updated economic assessment of various road pavement options for the SH20 Mt Roskill project, has further confirmed the economic benefits of concrete roads. The study revealed that of all the options available in 2002, when the initial SH20 Mt Roskill study occured, a concrete option would have had lower actual net present value capital costs, and lower gross present value cost investment and user costs, than the option chosen.

The case for concrete roads has gained further credence in the wake of the recent amendments to the NZTA’s Economic Evaluation Manual. Based on recommendations from the New Zealand Treasury, the NZTA has adjusted to 8% percent per annum (from 10%) the discount rate by which the  cost and benefits of infrastructure projects are determined over time. The evaluation period for infrastructure has also been extended from 25-years to 30-years. A lower discount rate would most likely favour infrastructure projects that reduce the total cost of maintaining and operating the network, that is to say, those major infrastructure projects that require the long service-life afforded through concrete.

Both these economic assessment factors for infrastructure projects now more accurately consider the range of advantages offered by concrete’s durability. Even so, they are still out of kilter with overseas practice. For instance, the current discount rates used by the UK Highways Agency are 3.5% up to 30-years, and then 3.0% from 31 to 60-years.

From an environmental perspective the performance of concrete roads is also very encouraging. Along with research supporting concrete roads as requiring minimal maintenance and therefore causing less congestion and associated exhaust emissions, concrete roads also enhance the fuel efficiency of heavy vehicles by reducing rolling resistance. Furthermore, a recent whole-of-life study also identified concrete manufacture as requiring less primary energy, and therefore generating less greenhouse gases, than alternative roading materials.

Another environmental factor, which elevates concrete roads for consideration within the RoNS, is that construction technology has advanced sufficiently over the past decade to address the issue of surface noise. Grind-and-groove surface technology as a means to improve surface noise characteristics of concrete roads is now commonplace in Australia and North America. Moreover, if the new draft standard DZ 6806 Acoustics – Road Traffic Noise – New and Existing Roads is approved to become NZS 6806, and is adopted by NZTA, it could favour diamond ground, longitudinally tyned plain concrete roads.

An interesting property of concrete, with positive environmental implications, which is attracting increased attention, is its albedo – the ratio of the reflected solar energy to the total solar energy received. Put simply, the light coloured surface of a concrete road has a greater albedo than darker alternative roading materials. This translates to greater radiation reflectivity, which in turn slows the process of global warming.

With the advantages of concrete roads clearly evident, now is the ideal time for key decision makers to take a fresh look at our road building philosophy, and begin to seriously consider concrete solutions. The range of benefits offered through concrete road construction complements the visionary scale of the RoNS and the current level of commitment shown by the government to their implementation. Future-proof our roading network now - with concrete.