#52 Effects of extreme heat on pavement

As reported in a previous brief, Australia faces the likelihood of more frequent and destructive extreme weather events in the coming decades. While the impacts of floods and storms on transport infrastructure are generally known and sometimes quantified, and future scenarios are predicted, the specific effects of extreme heat on pavement integrity are less often reported. This is relevant because extreme heat impacts pavement integrity without the additional destructive effects of floods, storms and fire. Research on the impacts of extreme heatwaves in Melbourne in 2009 found that road and rail infrastructure was significantly impacted, in addition to the 374 deaths reportedly associated with heat stress[1].

When road pavements heat up, they expand and soften. The extent of this expansion and softening depends on the amount of heat absorbed, the pavement design, and the materials used in its construction (e.g., asphalt or concrete). This can result in deformation such as buckling and rutting, which may be exacerbated by high traffic volumes and particularly heavy vehicle traffic. Cooler weather then causes pavements to contract, resulting in cracks and breaks which allow water ingress and accelerate the formation of potholes. Pavement design and construction generally allow for expansion and contraction within the limits of normal or expected temperature ranges, but these ranges may be exceeded in extreme weather events. As reported in a 2020 review of relevant research[2]

… the ability of asphalt materials to resist permanent deformation reduces as temperature increases. In extreme cases, when temperature has significant daily/hourly increases, accelerated development of permanent deformation can be expected... In addition, higher temperature can lead to faster aging of asphalt mixtures, and pavements can become more prone to cracking due to brittleness.

In the event of increases in the frequency of extreme heat events, a reduction in pavement design life can be expected under current pavement design and construction conditions. Addressing faults early through proactive pavement monitoring and repair is likely to extend pavement life. If the associated costs are not absorbed by road authorities, future costs may be borne by road users in terms of safety, vehicle maintenance and travel time.

[1] McEvoy et al., The impact of the 2009 heat wave on Melbourne's critical infrastructure. Local Environment, 17(8), 783–796.

[2] Qiao et al., Flexible Pavements and Climate Change: A Comprehensive Review and Implications. Sustainability 2020, 12(3), 1057.