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34 deicers containing KAc. A 50% KAc deicing solution is left deicers is a complex process that involves chemical and phys- in the base for 21 days at 194F. To pass, the base must have ical alterations in aggregates and cement paste. Deterioration no evidence of corrosion or leakage ("Specification for Air- of hot mix asphalt caused or accelerated by the PDPs is a less port Light Bases . . ." 2006). explored area. In addition, current understanding of the impact of modern PDPs on both PCC and asphalt pavements is mostly Finally, the only other information found concerning based on macro-level observations and testing of properties, deicers and airfield infrastructure is the possible reduction in whereas mechanisms underlying the critical physical and safety from dirty light fixtures. In 2002, the airfield duty chemical interactions are less known. Therefore, in-depth manager of the Manchester Airport in the United Kingdom research using advanced techniques is needed to advance the mentioned ". . . that deicing fluid makes light fixtures sticky knowledge base for better design, construction, and mainte- and more dirt sticks to them in the winter months" (Flight nance of pavement materials and to extend their service life in Safety Foundation Editorial Staff 2002). a cost-effective manner. CONCLUDING REMARKS In spite of their environmental advantages over older for- mulae such as urea and glycols, alkali-metal-salt-based PDPs Both traditional and modern PDPs have been observed to react present potential problems for the airfield infrastructure. with major pavement materials and deteriorate the integrity of Table 12 summarizes the effects of modern PDPs on airfield airport pavements. Deterioration of PCC pavements owing to infrastructure, including the key findings and knowledge gaps. TABLE 12 SUMMARY OF EFFECTS OF MODERN PAVEMENT DEICING PRODUCTS ON AIRFIELD INFRASTRUCTURE PDP Impact Information Sources What Is Known What Is Unknown 1. The last decade has seen an 1. There is a need for research increase in the premature data from controlled field deterioration of airfield PCC investigation regarding the 1. Academic-peer-reviewed pavements with the use of alkali- effects of alkali-metal-salt-based literature metal-salt-based PDPs. PDPs on concrete pavement. Impact of PDPs on 2. Industry-peer-reviewed concrete pavement publications and reports 2. Limited existing laboratory studies 2. There is a need to unravel the 3. Survey of stakeholder indicated that alkali-metal-salt-based specific mechanism by which groups deicers could cause or accelerate ASR alkali metal salts cause or distress in the surface of PCC promote ASR. pavement, by increasing the pH of concrete pore solution. 1. Although it was observed in some Nordic airfields that exacerbated 1. There is a need for research asphalt deterioration occurred with data from controlled field applications of alkali-metal-salt-based investigation regarding the 1. Academic-peer-reviewed PDPs, there is thus far little effects of alkali-metal-salt-based literature observation reported in U.S. or PDPs on asphalt pavement. Impact of PDPs on 2. Industry-peer-reviewed Canadian airports. asphalt pavement publications and reports 3. Survey of stakeholder 2. Significantly accelerated 2. There is a need to unravel the groups deterioration of asphalt pavements specific mechanisms by which was found in laboratories when alkali metal salts and other exposed to acetate/formate-based PDPs (e.g., bio-based deicers) deicers. deteriorate asphalt pavement. 1. Empirical evidence exists 1. Industry-peer-reviewed 1. No academic-peer-reviewed Impact of PDPs on indicating that PDPs are responsible publications and reports scientific information could be other airfield for damaging other airfield 2. Survey of stakeholder found to corroborate these infrastructure infrastructure (GSE, signage, lighting groups empirical observations. and other electrical systems). GSE = ground support equipment.