How can you use warm-mix asphalt in cold climates?

1 WMA production methods

Different methods exist to produce WMA, depending on the type of asphalt plant, binder, and additives used. Foaming is a popular method which involves injecting a small amount of water into the asphalt binder, creating steam and expanding the binder to reduce its viscosity and enable mixing and compaction at lower temperatures. Chemical additives such as surfactants, waxes, and organic acids can also be added to the asphalt binder or mix to modify its rheological properties and reduce its viscosity. Organic additives such as vegetable oils, animal fats, and polymers can also be blended with the asphalt binder to reduce its stiffness and improve its workability.

2 WMA performance in cold climates

WMA has been used successfully in many cold regions, such as Canada, Norway, Sweden, and Finland. However, there are some challenges that need to be addressed. Moisture damage is one of the main issues, since WMA may be more susceptible to it than HMA due to the lower production and compaction temperatures not allowing enough evaporation of moisture from the aggregate or the mix. This can weaken the bond between the aggregate and the binder, and cause cracking, raveling, and stripping. Additionally, WMA may be more prone to low-temperature cracking than HMA due to the higher air voids and lower binder stiffness which can reduce the thermal resistance and flexibility of the pavement. Low-temperature cracking occurs when the pavement contracts due to cold weather and exceeds its tensile strength. Furthermore, WMA may have a higher risk of rutting than HMA due to the lower binder viscosity and compaction density which can affect the stability and load-bearing capacity of the pavement. Rutting is defined as the permanent deformation of the pavement surface due to repeated traffic loads.

4 WMA benefits for cold climates

Despite the challenges, WMA offers some benefits for cold climates, such as the ability to extend the paving season, enhance workability, and reduce environmental impact. This can reduce costs and delays associated with seasonal shutdowns, improve the handling and transportation of asphalt, lower energy consumption and greenhouse gas emissions, and improve air quality. These advantages can lead to increased productivity and profitability of the paving industry, as well as improved health and safety of workers and the public.

5 Here’s what else to consider

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