Melting Points: The Asphalt Dilemma with Rising Temperatures

Hot mix asphalt is poured onto a driveway as the crew considers implications of rising temperatures

As the world grapples with the escalating impacts of climate change, a less talked about yet significant concern is emerging—the interaction between asphalt, rising temperatures, and the ensuing environmental and infrastructural challenges. With cities experiencing more days with temperatures soaring above 95°F, the traditional composition and utilization of asphalt is scrutinized.

How do rising temperatures exacerbate the issues surrounding asphalt?

Dr. Kevin Foster, who directs the Arizona Burn Center in Phoenix, emphasizes the immediacy of the issue by emphasizing how asphalt and concrete in direct sunlight can often reach surface temperatures as high as 180°F, which not only poses severe burn risks but significantly contributes to urban heat islands. During heatwaves, asphalt and concrete absorb and reflect a substantial amount of the sun’s energy, transferring the heat to the surrounding air, thereby escalating the overall air temperature​.

The World Economic Forum (WEF) highlights the emission concerns tied to asphalt. When exposed to moderate solar radiation, emissions from road asphalt can surge by up to 300%, illustrating that both solar radiation and temperature significantly influence asphalt emissions. This revelation underscores asphalt as a notable source of air pollutants in urban areas, further stressing the urgency to reconsider conventional asphalt compositions and applications in the face of climate change​.

Asphalt Performance in Rising Temperatures

As hotter days become more frequent, we must explore alternative materials that are less emission-intensive. The transition might not only mitigate the environmental impacts but also preserve the integrity of infrastructure, ensuring safer and more sustainable urban environments as the climate continues to change.

The Federal Highway Administration provides this table of issues, highlighting the need for more resilient roads materials.

Examples of Temperature-Affected Components
Change Impact
Affected Components
and Strategies

Rising Temperatures: Higher Average

Flexible Pavement

  • Increased maximum pavement temperature increases the potential for rutting and shoving, requiring more rut-resistant asphalt mixtures
    • May require raising high-temperature asphalt binder grade and/or increasing the use of binder polymerization and/or improved aggregate structure in asphalt mixes
    • Increased use of rut-resistant designs including thin, rut-resistant surfaces
  • Increased age hardening of asphalt binder
    • Use binders that age more slowly
    • Expanded use of asphalt pavement preservation techniques to address binder aging

Rigid Pavement

  • Increased potential for concrete temperature-related curling (and associated stresses) and moisture warping
    • Greater consideration of concrete coefficient of thermal expansion and drying shrinkage
    • Incorporation of design elements to reduce damage from thermal effects including shorter joint spacing, thicker slabs, less rigid support, and enhanced load transfer

Rising Temperatures:

Higher Extreme

In addition to strategies listed above:

  • Higher extreme temperature may impact construction scheduling, requiring work to more often be conducted at night
  • If accompanied by drought, increased potential for subgrade shrinkage

Flexible Pavement

  • Increased potential for asphalt rutting and shoving during extreme heat waves
    • See strategies above, but recognizing that the historical basis for selecting binder grades may no longer be valid

Rigid Pavement

  • Increased risk of concrete pavement blowups due to excessive slab expansion
    • Use shorter joint spacing in new design
    • Keep joints clean and in extreme cases, install expansion joints in existing pavements

Learn about Modern Asphalt’s low-carbon materials and resiliency.