Xianming Shi

Managing Metallic Corrosion on Winter Maintenance Equipment Assets

Many metallic components in highway maintenance equipment fleet are at risk of corrosion, which is exacerbated in service environments where roadway deicers have been applied. Roadway deicers generally feature chloride salt(s) as their freezing point depressant. As such, the exposure to roadway deicers poses a substantial risk to highway maintenance equipment. This work will review best practices available to manage the risk of deicer corrosion to equipment assets and present a user’s manual for the use of maintenance agencies in the northern climate. The manual has addressed the following subjects: Corrosion Basics; Causes and Effects of Corrosion; Materials Used for Snow and Ice Control; New Equipment Specification; Repair, Rehabilitation and Retrofitting of Existing Equipment; Preventive Maintenance Practices; Training and Facility Management. This manual would be applicable to the winter maintenance community and could aid agencies in the prevention of metallic corrosion and the extension of service life and reliability/readiness of equipment assets.

Water Quality Implications and the Toxicological Effects of Chloride-Based Deicers

Traditionally, the main priority of winter road maintenance has been assigned to level of service, cost-effectiveness, and corrosion rather than other less well-characterized effects such as impacts to water quality. It is increasingly vital to understand the environmental footprint of deicers, including their impacts on aquatic ecosystems. Chloride based deicers do not degrade in the natural environment and their application on winter pavements can lead to accumulation in adjacent environments over time. Information presented to date on deicers generally includes chemical composition and performance of deicers, while additional information on deicer aquatic toxicity is needed to enable fully-informed decisions by stakeholders. This work presents a state-of-the-knowledge review of the impacts of chloride based deicers and additives on water and aquatic species, and the issue of heavy metal leaching. Toxicity associated with the direct effect of deicers or with the indirect effect via their interactions with runoff chemistry is reviewed as well. This work will assist the stakeholder agencies in the search for effective practices to reduce the toxicity and other water quality implications of chloride based deicers.

Deicer Impacts on Concrete Bridge Decks: A Comparative Study of Field Cores from Potassium Acetate and Sodium Chloride Environments

The use of chemical deicers in cold regions has raised concerns over their potential negative effects on the performance and durability of concrete infrastructure. Extensive studies have been conducted in the laboratory setting, often in an accelerated manner, which reported the chemical and physical deterioration of concrete as a function of deicer type. Yet, little research has been published on how the deterioration of concrete bridge decks in the field environment is affected by their exposure to deicers, where the durability of concrete is also affected by temperature cycles and mechanical loadings. This work reports a comparative study of field cores taken from two select Nebraska concrete decks and from two select Utah concrete decks. The Nebraska decks had been exposed to mainly potassium acetate (KAc) deicers, whereas the Utah decks had been exposed to mainly sodium chloride (NaCl) deicers. The field cores were tested for their mechanical properties and transport properties. They were also subjected to staining tests to detect possible chloride penetration, carbonation, and aggregate silica reaction (ASR), and subjected to petrographic analysis to characterize their paste and air contents. The concrete cores from Nebraska exhibited more significant degradation, relative to those from Utah. Specifically, the exposure to KAc deicer led to significant reduction in mechanical properties (compressive strength, splitting tensile strength, and microhardness) and more signs of ASR. This case study sheds some light on this complex issue of concrete durability and raises the awareness over the risk of using KAc deicers on concrete structures and components.

Impacts of Specialized Hauling Vehicles on Highway Infrastructure, the Economy, and Safety: Renewed Perspective

In the United States, the Federal Bridge Formula (FBF) has been used to set the Gross Vehicle Weight (GVW) limit and axle weight limit for various vehicle configurations. Further, the American Association of State Highway and Transportation Officials (AASHTO) developed a set of legal loads that closely match the FBF in the short, medium, and long truck length ranges and are used to evaluate the need for bridge weight limit posting. Specialized Hauling Vehicles (SHVs) were developed in recent years and they play an important role in the trucking industry. Typically, SHVs refer to single unit (SU) vehicles with closely spaced multiple axles that can carry up to 80,000 pounds. Even though SHVs meet the requirement under FBF, these newer axle configurations were not considered in the original development of the FBF and AASHTO legal loads. As such, FBF does not adequately restrict SHVs and most likely overstress the bridges. This study was conducted to examine the current knowledge related to the impact of SHVs on highway infrastructures, economy, and safety. The key findings from the study include: (1) Relative to conventional trucks, SHVs may not induce significant damage to asphalt pavements and can potentially induce additional damage to concrete pavements; (2) Relative to conventional trucks, SHVs can induce significant damage to short span bridges particularly to short span timber and steel bridges; (3) Bridge weight limit posting is expected to increase with the allowance of SHVs; and (4) SHVs are likely to benefit economy and safety. Findings of the study will contribute to environmentally sustainable highway infrastructure in the presence of SHVs.