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25 CHAPTER FOUR EFFECTS OF PAVEMENT DEICING PRODUCTS ON AIRFIELD INFRASTRUCTURE The use of traditional PDPs consisting of urea and/or glycols fort 2000). In a report produced by the Transportation Asso- has become diminished on airfields as a result of their adverse ciation of Canada, it is stated that with good pavement design environmental impacts. Modern PDPs often include KAc, and construction, the effects of winter maintenance chemicals NaAc, and NaF as the freezing point depressant, with other may be minimized ("Synthesis of Best Practices . . ." 2003). additives. More recent field and laboratory experience, however, This chapter synthesizes the effects of airport PDPs on indicates probable impacts of alkali-metal-salt-based PDPs pavement and other airfield infrastructure. The results of the on both PCC and asphalt pavements (Nilsson 2003, 2006; ACRP survey distributed for this project are assimilated Rangaraju et al. 2006; Pan et al. 2008). To reexamine the within the sections concerning effects on concrete pavement, case, a portion of the survey for this synthesis was designed asphalt pavement, and other infrastructure. In addition to the to gather input regarding the impacts of deicers on airfield information obtained from the survey, the majority of this pavement and infrastructure. The ACRP survey was distrib- chapter synthesizes published data from a comprehensive lit- uted to professionals representing the 50 busiest airports erature review. in the United States, among others. A total of 17 respon- dents were directed to this section of the survey based on an PAVEMENT DEICING PRODUCTS EFFECTS ON assessment of their initial responses. Among them, 14 were AIRFIELD INFRASTRUCTURE: FIELD EXPERIENCE employed by airports, 12 of which are in the United States. Three additional respondents represented the Swedish Civil This section reports on the field experience regarding the Aviation Administration (whose responses were specific to effects of PDPs on the durability of airfield infrastructure. It the GothenburgLandvetter Airport), the Innovative Pave- should be noted that any pattern derived from such field data ment Research Foundation (IPRF), and the FAA. As such, should be treated with caution and needs validation from the survey results provide information from a total of 15 air- research conducted in a well-controlled laboratory setting ports. Ten of these 15 respondents indicated that their job because the durability of airfield infrastructure is affected by title contained the word "Environmental"; other key words a wide variety of factors. The lack of documentation and/or included Manager, Director, Coordinator, Administrator, control of other variables in the field environment presents a Supervisor, Program, Deicing, Operations and Maintenance, challenge for researchers to unravel the specific role played Compliance, and Wastewater. Often the respondents con- by the PDPs or to quantify their impact. For instance, the dif- sulted their pavement engineers before responding to some ference in the performance of portland cement concrete technical questions in the survey. (PCC) pavements at two airports could be potentially attrib- uted to the use of not only different PDPs, but also different Four airports responded with detailed information about types of aggregates (reactive vs. nonreactive), among many the specific use of PDPs: the type, application rate, applica- other variables (e.g., mix design, construction quality, cli- tion frequency, and total amount applied for each of the pre- matic conditions, and traffic loading). vious five seasons. In general, the results indicated increased use of KAc and less or no use of urea. For those that reported Telephone interview results of 12 (primarily Canadian) using both NaAc and NaF, the former has been used more airports/airport authorities conducted by George Comfort in frequently in the recent seasons. 2000 indicated increased use of alkali-metal-salt-based PDPs (KAc, NaAc, and NaF) over urea. A majority of respondents Even though most responses to the ACRP survey indi- to the interview indicated that pavement damage was not cated little field observation or concern regarding the impacts attributed to deicers, whereas four respondents suggested that of PDPs on the durability of airfield infrastructure, this may no conclusive statements could be made. A few isolated not necessarily represent the overall situation of U.S. airports responses to the interview indicated that crack and joint considering the limited number of responses. Seven ques- sealant might be affected, although no conclusive statements tions solicited information regarding the role of PDPs in dete- could be made to implicate aircraft or airfield deicers. Addi- riorating pavements, ground support equipment (GSE), light- tionally, two airports noted that KAc might provide an addi- ing fixtures, signage, and other infrastructure assets; the tional benefit of removing rubber buildup on runways (Com- lifespan and design and material changes of these were also