Saskatoon asphalt project tests cold weather road mixes

Key Takeaways:

• The University of Saskatchewan and the City of Saskatoon are collaborating on research to develop asphalt mixes and construction methods that can be used in colder temperatures, allowing the construction season to be extended.
• The project will test warm mix asphalt and additives that improve paving performance in low temperatures, helping reduce potholes and surface damage caused by cold-weather compaction.
• The research also explores incorporating recycled materials and uses USask’s testing facilities to evaluate roadway performance, aiming to provide practical guidance for municipalities and contractors in cooler conditions.

The Whole Story:

The University of Saskatchewan and the City of Saskatoon are partnering on a research initiative to develop asphalt mixes and construction methods that can be applied in colder temperatures, extending the construction season in the province.

Dr. Haithem Soliman, an associate professor of civil, geological and environmental engineering at USask, is leading the project with support from the Research Junction initiative, which funds research addressing local priorities.

The challenge is straightforward: traditional asphalt must be heated and compacted at high temperatures to achieve proper density and durability. When laid in cold conditions, it develops air voids that fill with water, freeze and crack—similar to a sealed bottle expanding when frozen—creating potholes and surface damage. Saskatchewan’s short summers and unpredictable fall weather compress the construction window, forcing projects into September and October.

“If we have a condition that we need to pave at cold air temperatures, we can recommend different materials or different mix designs,” Soliman said in a news release. “That is the objective.”

The research will explore warm mix asphalt, which can be compacted at lower temperatures than conventional asphalt, as well as additives that could allow laying and compaction at even lower temperatures. This flexibility would allow contractors to extend paving operations beyond the traditional summer window.

Matthew Hiltz, the City of Saskatoon’s asset preservation manager, said the project will help the municipality understand how cold-temperature paving affects road service life and identify the most effective methods for cooler conditions.

“Ultimately, we’re trying to find ways to extend the construction window before winter arrives,” Hiltz said in the release.

Soliman’s broader research program incorporates recycled materials—including plastic waste—into roadway construction. USask’s Multi-purpose Soil Testing (MOST) Facility houses a truck load simulator that allows researchers to test unpaved roadway designs under various conditions.

“This is my first direct research collaboration with the City of Saskatoon, and we’re having a good connection in terms of pavement research,” Soliman said.