Building Roads for a Changing Canadian Climate: What Asphalt Design Needs to Account For

A road is designed on the day it is built, but it performs in the climate that follows.

That distinction matters more as infrastructure service lives stretch decades into a changing Canadian climate.

Canada's latest national climate assessment reports that the intensity and frequency of hot extremes have increased and are projected to increase further across the country. Extreme precipitation has also intensified at the national scale, with continued change expected as warming increases.^[1] For pavement owners, these are not abstract environmental statistics. Temperature and water directly influence materials, subgrades, drainage, deterioration and maintenance.

The result is a practical design question: are we selecting asphalt for yesterday's conditions, or for the conditions a pavement is expected to experience throughout its life?

Asphalt is temperature-sensitive by design

Asphalt binder changes behaviour with temperature.

At high temperatures and under loading, the pavement must resist permanent deformation and rutting. At low temperatures, it must tolerate thermal contraction without excessive cracking. That is one reason performance-graded asphalt systems relate binder selection to expected pavement temperatures. AASHTO's PG specifications are explicitly tied to maximum and minimum pavement design temperatures.^[2]

Traffic adds another dimension. Slow, heavy or repeated loads can increase high-temperature stress, which is why modern MSCR-based binder specifications distinguish loading conditions as well as climate.^[3]

Climate resilience therefore begins with matching material properties to a clearly defined exposure.

The future exposure may differ from the historical exposure

The National Research Council of Canada has already translated this issue into a practical tool. Its Performance-Graded Asphalt Cement under a Changing Climate, or PGAC³, application was developed to help Canadian airports assess minimum required asphalt-cement performance grades under projected future climate conditions through the end of the century.^[4]

The tool is airport-focused, but the principle is broadly important: materials selected for long-lived infrastructure can be assessed against the climate expected during their service period, not merely the historical climate used in older design assumptions.

Canadian research has similarly concluded that climate change can alter pavement environmental loading and that resilient flexible pavements should consider future heat, precipitation, freeze-thaw cycles and extreme weather.^[5]

Heat is only part of the resilience problem

A common simplification is to equate climate-resilient asphalt with “heat-resistant asphalt.” That is too narrow.

Higher pavement temperatures can increase rutting risk. Low temperatures remain relevant to thermal cracking even as average cold extremes change. Moisture can weaken vulnerable material systems and contribute to stripping or structural deterioration. Heavy precipitation puts greater demands on drainage and surrounding infrastructure. Freeze-thaw behaviour remains important in many Canadian locations, especially where water reaches pavement or foundation materials.

Traffic does not pause while those environmental mechanisms occur.

The right objective is therefore not maximum stiffness or maximum flexibility. It is balanced performance across the conditions that matter at a specific site.

Better materials selection is one layer of resilience

Infrastructure resilience operates at several levels.

The pavement structure must be suitable for traffic and foundation conditions. Drainage has to move water effectively. Construction quality has to achieve the intended density and geometry. Maintenance must occur at the right time.

Within that system, binder and mixture design determine how the asphalt layer responds to temperature and loading.

Polymer modification can be useful where additional high-temperature, low-temperature or fatigue performance is required. FHWA has documented applications of polymer-modified binders in high-stress and extreme-climate conditions, with potential benefits in rutting and cracking performance.^[6]

The important word is potential. Climate resilience should be demonstrated through the properties of the final binder and mixture, not assumed from the presence of an additive.

Test the mixture against the failure modes you care about

Traditional material specifications remain essential, but performance-oriented testing can provide additional evidence about how a proposed mixture behaves.

FHWA's asphalt testing resources include tests addressing cracking, rutting and moisture susceptibility, while its Balanced Mix Design initiative focuses on achieving acceptable performance across competing distress mechanisms.^[7]

This is especially relevant when introducing modifiers, recycled materials or other formulation changes. A change that improves one property may affect another.

For climate-resilient pavement, a sensible testing plan begins with the location and project risk:

What pavement temperatures are expected now and later in the asset's life? What traffic loading will the pavement see? Is low-temperature cracking a critical concern? Is rutting historically problematic? How significant are moisture and drainage risks? Will the mixture include RAP? What performance tests best represent those risks?

Answering those questions produces a defensible materials strategy.

Resilience is also an economic strategy

Climate-related infrastructure deterioration has direct financial consequences. Housing, Infrastructure and Communities Canada notes that climate change can shorten the useful life of infrastructure and increase operations, maintenance, retrofit and replacement costs, including for roads.^[8]

This gives durability a business dimension.

An adaptation measure may raise initial project cost. But if it meaningfully delays rehabilitation, reduces maintenance or lowers the probability of early failure, the correct comparison is not simply the material invoice. It is the life-cycle outcome.

This is where resilience, sustainability and economics start to converge.

A pavement that lasts longer can require fewer raw materials and fewer construction interventions over the analysis period. A design that tolerates future conditions can reduce exposure to unplanned repairs. And an evidence-based specification gives owners a clearer basis for comparing alternatives.

Designing for the road ahead

Polyversa's stated mission is to advance durable, environmentally responsible pavement and surface solutions, with its polymer-development work focused on properties including binding and temperature resilience.

For those goals to translate into climate resilience, the standard should be measurable performance.

The best question is not “Is this a climate-resilient product?”

It is:

“Which future conditions are we designing for, which failure modes are we trying to control, and what evidence shows that this material system is better equipped to handle them?”

Canadian infrastructure will experience conditions throughout its service life that are not identical to those of the past. Our material-selection methods should acknowledge that reality.

Design the pavement for the climate it will live in—not simply the climate recorded before it was built.