HOW CONCRETE ROADS COMBINE SUSTAINABILITY AND RESILIENCE

at the recent

Poland, attended by

Awhite paper by the American Concrete Pavement Association (ACPA), ‘Concrete Pavements’

Role in a Sustainable, Resilient Future’ was presented at the symposium to underline the issue.

Perrie says concrete roads’ resilience is a particularly strong factor to consider by decision-makers for infrastructural development. “Sustainability deals with known events that can be quantified. Resilience, on the other hand, is the ability to anticipate, prepare for and adapt to changing conditions as well as withstand, respond to and recover rapidly after a disruptive event. In a changing global climate where extreme weather events are now becoming increasingly frequent, with far higher intensity than in the past, it is impossible to have sustainable infrastructure without resilience,” he explains.

Resilient systems limit the impact of relatively unexpected adverse effects such as storms, floods and droughts, like those experienced recently in KwaZulu-Natal and the Eastern Cape. “The challenge is how to build more durable concrete structures while minimising the carbon emissions generated in producing and supplying cement and concrete,” he continues.

Life-cycle benefits

Perrie says the South African cement industry has already committed to net-zero carbon emissions by 2050. “While this focuses on cement’s value chain, it is also important to focus on the concrete value chain with a whole lifecycle approach – from material production through pavement design, construction, use stage, maintenance and preservation, and endof-life reuse or recycling. The essential tools for this are full life-cycle cost analysis (LCCA) and life-cycle assessment (LCA). While some life-cycle assessment is done in South Africa, it often does not include the full LCA, including road-user delay costs during maintenance,” he expands.

As Perrie points out, it is critically important to address climate change and carbon reduction, but also essential to recognise that every roads agency, province and municipality is facing budget constraints, often being forced to make decisions based purely on economic factors. Where LCCA is carried out, in areas where there is minimal data on concrete roads, the results are frequently heavily biased.

The best way to improve the economic side of sustainability is to recognise the benefits of industry competition. According to the Massachusetts Institute of Technology (MIT) Concrete Sustainability Hub, US state agencies that have sustained a consistent competitive roads market – using both asphalt and concrete pavements over multiple years – pay lower prices for all paving materials. The US, with the highest level of competition, has unit prices that are 29% lower for concrete and 8% lower for asphalt.

Perrie says that, while the environmental benefits of concrete roads are considerable, numerous easy and minor alterations can be implemented to improve the environmental impact of concrete. These include:

• optimising pavement designs to ensure minimum quantities of materials

• reducing concrete’s carbon footprint by using extended cements appropriately

• formulating concrete mix designs with optimised aggregate grading and optimised cement content.

Concrete pavements, because of their inherent stiffness, strength, brightness and durability, can also significantly reduce roads’ usage phase due to:

• fuel savings, particularly for heavy vehicles

• increased albedo or reflectivity, which minimises urban heat islands and can reduce required lighting at night.

CO2 absorption

One of concrete’s unique properties is its ability to act as a CO2 ‘sink’ for the planet. As concrete ages it absorbs carbon dioxide, helping to offset the amount produced when making cement. Covering concrete pavements with asphalt, either at construction or during the use phase, prevents this happening.

“Diamond grinding to provide an acceptable riding quality at construction or to improve it during the usage phase would increase CO2 absorption and be a far more sustainable practice, as would the use of concrete overlays for upgrading existing asphalt roads,” adds Perrie.

It should also be remembered that concrete is 100% recyclable and can be reused on the same site for base material, aggregate for new concrete and as filler.

“Concrete provides the most sustainable as well as resilient choice for pavement systems. Its long lifespan provides the greatest economic value over the long term for taxpayers and end-users with many environmental benefits. Choosing concrete roads for South African infrastructure is ultimately the most responsible choice for both sustainability and resilience,” he concludes.

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