Impacts of Airport Pavement Deicing Products on Aircraft & Airfield Infrastructure
Started: March, 2007 Ended: November, 2007 Project ID #4W1527 Status: Completed
Results & Findings
Researchers will determine through the collection and assessment of available data whether the use of particular PDPs have been seen to result in damage to pavements or aircraft components, and whether adjusting PDP formulations can mitigate those effects. The research may also result in suggestions for modifications in the manufacture of components and the construction of runways.
The objectives of this synthesis are to report how airports chemically treat their airfield pavements to mitigate snow and ice, and what chemicals are used; to review damage reported to aircraft components and airfield infrastructure in association with the use of traditional or modern pavement deicing products (PDPs); and to identify critical knowledge gaps on these subjects.
Airfield pavement deicing and anti-icing are essential activities to maintain safe winter operations of the aviation industry. Airfield pavement deicing products (PDPs) traditionally consisting of urea or glycols have become less popular due to their adverse environmental impacts. New PDPs have emerged as alternatives that often contain potassium acetate (KAc), sodium acetate (NaAc), sodium formate (NaF), or potassium formate (KF) as the freezing point depressant. When it comes to airfield pavement deicing and anti-icing, there are no simple solutions to the competing, and sometimes conflicting, objectives of aircraft safety, environmental regulatory compliance, materials compatibility, and operational implementation viability. More than a decade of experience in the use of these new product formulations has resulted in reports that suggest possible impacts on aircraft components and airfield infrastructure. This report provides the synthesis of results from ACRP Project 11-03, S10-03 Impact of Airport Pavement Deicing Products on Aircraft and Airfield Infrastructure. The objectives of this synthesis are to report how airports chemically treat their airfield pavements to mitigate snow and ice and chemicals used; to review damage reported to aircraft components and airfield infrastructure in association with the use of traditional or modern PDPs; and to identify critical knowledge gaps on these subjects. Responses representing approximately 100 airports were gathered from the recent U.S. Environmental Protection Agency (USEPA) 2006 questionnaire, which indicated that KAc and sand are most widely used at U.S. airports for snow and ice control of airfield pavements, followed by airside urea, NaAc, NaF, propylene glycol-based fluids, ethylene glycol-based fluids, and others. CATALYTIC OXIDATION OF CARBON-CARBON COMPOSITE BRAKES Catalytic oxidation of aircraft carbon-carbon (C/C) composite brakes due to airfield PDPs has become a growing concern to be monitored in the ever-changing operation environment. The scientific evidence indicates that potassium and sodium in modern PDPs contribute to the more rapid structural failure of C/C composite brakes observed in recent years. To ensure safety, this concern is being addressed through more frequent pro-active maintenance/inspection activities, which result in significantly increased direct and indirect costs. Although the fundamental mechanisms of catalytic oxidation by PDPs are well understood in well-controlled laboratory settings and advances in technologies for its prevention and mitigation have been made in the last decade or so, the problem seems far from solved. There is still a need to establish a comprehensive PDP catalytic oxidation test protocol. Furthermore, research is needed to better understand relationships between brake design, anti-oxidant treatment, and PDP contamination as factors in catalytic oxidation. CADMIUM CORROSION Field reports increasingly suggest that the contact with modern PDPs promotes damage to aircraft components, especially cadmium (Cd)-plated components. Until recently, the principal evidence connecting alkali-metal-salt PDPs with Cd-plating corrosion has been that a trend of increased reports of the latter occurred concurrently to the introduction of the former. Although the fundamental mechanisms of Cd corrosion in water are relatively well studied, the link between alkali-metal-salt based PDPs and Cd-plating corrosion has yet to be experimentally validated and thoroughly investigated. There is still a need to establish a comprehensive metallic corrosion test protocol for PDPs. More research is needed to better understand the interactions among the aircraft component design, the corrosion-inhibiting compounds (CICs) used, and the contamination of PDPs in the processes of metallic corrosion. Finally, there is still a lack of academic research data from controlled field investigation regarding the aircraft metallic corrosion by PDPs. INTERACTION WITH AIRCRAFT DEICING AND ANTI-ICING FLUIDS Alkali-metal-salt based PDPs accelerate the precipitation and buildup of thickener residues from modern aircraft deicing/anti-icing fluids (ADAFs). The contamination effects of ADAFs by runway deicing fluids have been well-observed but not yet thoroughly quantified. Acquisition of hard data will assist in the generation of inspection schedules, and may spur development of improved thickener formulae for ADAFs. Research will be needed to better understand the interactions between ADAFs and PDPs, as new ADAFs and PDPs are continually introduced to the market. IMPACT OF PAVEMENT DEICING PRODUCTS ON CONCRETE PAVEMENT The last decade has seen an increase in alkali-silica reaction (ASR) occurrence with the use of alkali-metal-salt based deicers applied on airfield Portland cement concrete (PCC) pavements. Limited existing laboratory studies indicated that these modern PDPs could cause or accelerate ASR distress in the surface of PCC pavement, by increasing the pH of concrete pore solution. There is a need for research data from controlled field investigation regarding the effects of alkali-metal-salt based PDPs on concrete pavement. Furthermore, t here is a need to unravel the specific mechanism by which alkali metal salts cause or promote ASR. IMPACT OF PAVEMENT DEICING PRODUCTS ON ASPHALT PAVEMENT Concurrent to the use of acetate/formate-based deicers in the 1990s, asphalt pavement in Europe saw the increase in pavement durability problems. The damaging mechanism of asphalt pavement by modern PDPs seemed to be a combination of chemical reactions, emulsification and distillation, as well as generation of additional stress inside the asphalt mix. There is a need for research data from controlled field investigation regarding the effects of alkali-metal-salt based PDPs on asphalt pavement. Furthermore, there is a need to unravel the specific mechanisms by which alkali metal salts and other PDPs (e.g., bio-based deicers) deteriorate asphalt pavement. IMPACT OF PAVEMENT DEICING PRODUCTS ON OTHER AIRFIELD INFRASTRUCTURE Other airfield infrastructure that comes into contact with PDPs includes ground support equipment (GSE), signage, lighting and other electrical systems. Empirical evidence exists indicating that PDPs are responsible for damaging such infrastructure. However, no academic-peer-reviewed scientific information could be found to corroborate these empirical observations.
Xianming Shi - PI
Gail Staba - Main External Contact
Files & Documents
Sponsors & Partners
- Transportation Research Board (TRB) Sponsor
- National Academy of Science (NAS) Co-Sponsor