Program Overview

The Western Transportation Institute's Winter Maintenance and Effects Program seeks to research and mitigate corrosion and winter effects on transportation systems through innovation and multi-disciplinary partnerships.

Vision

• Develop, test and evaluate materials, technologies, and systems to support winter maintenance best practices and decision making.
• Investigate and mitigate the impact of deicers, freeze-thaw cycles, and other winter conditions on material behavior and performance.

Winter Maintenance Challenges

In the northern United States and Canada, snow and ice control operations are essential to ensure the safety, mobility and productivity of winter highways, where the driving conditions are often worsened by inclement weather. The United States alone spends $2.3 billion annually to keep roads clear of snow and ice.

Depending on the road weather scenarios, resources available and local rules of practice, departments of transportation (DOTs) use a combination of tools for winter road maintenance and engage in activities that include anti-icing, deicing, sanding and snowplowing. As the detrimental environmental impacts of abrasives are generally greater than those of chemicals, DOTs have begun to minimize the use of abrasives. Currently, the United States applies approximately 15 million tons of salts each year. The increased use of chemicals, however, has raised growing concerns over their effects on motor vehicles, the transportation infrastructure, and the environment.

Maintenance agencies are continually challenged to provide a high level of service (LOS) and improve safety and mobility in a cost-effective manner while minimizing corrosion and other adverse effects to the environment. To this end, it is desirable to use the most recent advances in the application of anti-icing and deicing materials, winter maintenance equipment and vehicle-based sensor technologies, and road weather information as well as other decision support systems. Such best practices are expected to improve the effectiveness and efficiency of winter highway operations, to optimize material usage, and to reduce associated annual spending and corrosion and environmental impacts. For instance, the Pacific Northwest Snowfighters Association (PNS), consisting of the transportation agencies in the states of Washington, Oregon, Montana, Idaho, Colorado, and British Columbia, has strived to "serve the traveling public by evaluating and establishing specifications for products used in winter maintenance that emphasize safety, environmental preservation, infrastructure protection, cost-effectiveness and performance."

In recent years, transportation agencies across North America have been shifting from reactive strategies to proactive strategies for snow and ice control, such as anti-icing. Compared with traditional methods for snow and ice control (e.g., deicing and sanding), anti-icing leads to decreased applications of chemicals and abrasives, decreased maintenance costs, improved level of service, and lower accident rates. Reliable weather forecasts are key to a successful anti-icing program, as the pavement surface temperature dictates the timing for anti-icing applications and the appropriate application rate.

The crux is to strike the right balance in meeting multiple goals of maintenance agencies, including safety, mobility, environmental stewardship, infrastructure preservation, and economics. A considerable amount of research is still needed in order to fill the knowledge gap and establish a scientifically robust, defensible decision-making process for winter maintenance.

Corrosion and Winter Materials Challenges

It is in the national interest to achieve better understanding of corrosion and its control and thus reduce the high costs directly or indirectly attributable to corrosion, as the serious consequences of corrosion have become a problem of worldwide significance. The annual direct cost of metallic corrosion ranges from 3.1 percent to 4.5 percent of the gross domestic product (GDP) in industrialized countries. According to a study by the Federal Highway Administration (FHWA), the impact of corrosion on the U.S. economy runs to $276 billion annually, of which 25 to 30 percent could be saved by employing optimum corrosion management practices.

Corrosion of prestressed and normally reinforced concrete structures is a major and increasing problem worldwide, as it often leads to the premature failure of such structures with serious economic and safety implications. For the transportation infrastructure, corrosion may significantly reduce its strength, serviceability, and aesthetics. In the United States, billions of dollars have been spent to provide corrosion protection for concrete structures, including highway bridges. The remediation of concrete bridges, undertaken as a direct result of chloride-induced corrosion of the reinforcing steel, would cost U.S. highway departments $5 billion per year. Corrosion is also a great concern for the durability of pipelines and earth-retention systems.

To clear the roads of snow and ice, approximately 20 million tons of chloride-based road salts are applied across North America each year. There are growing concerns over their corrosive impacts on motor vehicles and the transportation infrastructure. For reinforced concrete structures, such as highway bridges, in cold regions the corrosion problem is further complicated by the freeze-thaw cycles and wet-dry cycles they experience. A significant amount of research is still needed in order to address the corrosion and materials integrity issues in cold regions.

Deicing and anti-icing chemicals (or deicers) have been observed to react with major pavement materials and deteriorate the integrity of airport and highway pavements. Deterioration of Portland cement concrete (PCC) pavements due to deicers is a complex process that involves both physical and chemical alterations in aggregates, cement paste or steel. Concrete deterioration is affected by factors such as the deicer chemistry, cement ingredient and aggregate reactivity, and is further complicated by environmental conditions, mainly the wet/dry and freeze/thaw cycling. Deterioration of hot mix asphalt (HMA) caused or accelerated by deicing and anti-icing chemicals is a relatively unexplored area. Little research has been conducted to assess the deicer effects on HMA pavements, even though there are reports of stripping occurring on asphalt pavements exposed to deicers.

Current understanding of deicer impact on pavements is mostly based on macro-level observations and testing of properties, whereas mechanisms underlying the critical physical and chemical interactions are poorly known. Therefore, in-depth research utilizing electrochemical, surface analytical, and other advanced techniques is needed in order to advance the knowledge base for better design, construction and maintenance of pavement materials and to extend their service life in a cost-effective manner.

Contact:
Xianming Shi, Ph.D.
xianming_s@coe.montana.edu
406-994-6486