This laboratory study developed and tested an anti-icing asphalt pavement that incorporated innovative salt-storage additives with a sustained salt-release rate.
To reduce the use of abrasives and to improve the efficiency of mechanical ice removal, transportation agencies apply large amounts of deicing and anti-icing chemicals every year. Although these chemicals are undoubtedly beneficial, there are growing concerns over the short-term and long-term risks associated with the use of deicers, including the potentially adverse impacts of salt chemicals on the natural environment, vehicles, and the transportation infrastructure.
Anti-icing asphalt pavement that incorporates salt-storage additives holds promise as an effective strategy to not only prevent ice formation or weaken the bond of snow-ice to the pavement but also to reduce the use of salt chemicals for winter road maintenance. However, this strategy still faces questions, such the longevity of the anti-icing ability, its low-temperature effectiveness, and potentially adverse impacts on the mechanical properties of the asphalt pavement.
This project developed a new asphalt additive intended to be blended into asphalt pavement for in-situ anti-icing without compromising the pavement’s durability. The salt-storage additives were developed with a low salt-release rate. They were prepared though a surface treatment approach in which zeolite containing calcium chloride (CaCl2) was coated with a porous epoxy layer. The additives were tested at three sizes, and the CaCl2 content in the additives ranged from 20.1 percent to 21.1 percent.
Laboratory evaluation of the asphalt mixtures for the additives consisted of fog-freezing friction tests at 25°F and 15°F to determine anti-icing capacity, anti-icing longevity tests at 59°F and 32°F to estimate the effective anti-icing period, Hamburg wheel-track tests in water at 122°F for assessing the moisture susceptibility and rutting resistance of the asphalt mixture, and indirect tensile tests to determine the mid-temperature (77°F) and low temperature (14°F) cracking resistance of the asphalt mixture.
The results indicated that the laboratory prepared additives benefited the anti-icing performance of the asphalt pavement. The anti-icing capacity of the asphalt mixture significantly improved with the incorporation of the additives at both testing temperatures. Reducing the size of the additive further improved the asphalt’s anti-icing capability. Under simulated conditions the estimated effective anti-icing period of the asphalt pavement, depending on the size of the additive, ranged from 5.8 years to 15.3 years.
In addition, incorporation of the additives had a negligible effect on the asphalt mixtures’ resistance to moisture damage, and almost all the mixtures passed Washington State Department of Transportation specifications, as well as Wisconsin and Iowa specifications. The rutting resistance, mid-temperature (fatigue) cracking resistance, and low-temperature (thermal) cracking resistance of the asphalt mixture also improved, to various extents, with the addition of the anti-icing additives.
Authors:
Yan Zhang
Xianming Shi
WSU Department of Civil and Environmental Engineering
Sponsor: Center for Environmentally Sustainable Transportation in Cold Climates