Effects of Runway Deicers on Pavement Materials and Mixes: Comparison with Road Salt

Every year, large amounts of pavement deicing chemicals are used for snow and ice control on Canadian highways and airports. Until recently, urea had been the only pavement deicing chemical in use at Canadian airports, but due to recent concerns about the impact of this deicer on the environment, consideration has been given to replacing it with more environmentally friendly deicers. Concerns have also been expressed regarding the impact of road salts, which are used exclusively on highways but not airfields, on the environment. However, before substituting these conventional deicers with new ones, the potential deleterious effects of the new deicers on the pavement need to be quantified and compared with those of the conventional deicers. This paper presents an investigation to compare the destructive effect of newly introduced deicing chemicals such as potassium acetate and sodium formate, with urea and ordinary road salts on the durability of pavement construction aggregates and asphalt concrete when subjected to freeze-thaw cycles while submerged in solutions of different concentrations. The destructive effect of each deicer on aggregates was determined in terms of percent weight loss due to breakdown. For pavement samples, it was quantified in terms of weight and density loss, change in mechanical properties, variation in the penetration of recovered asphalt, and variation in the gradation of recovered aggregates. The test results showed that for all deicers the critical concentration, the one that caused the greatest damage to the aggregate, was in the 1–2% range, and for all deicers the quartzite aggregate suffered more damage than the limestone. It was also found that the road salt produced comparable damage to that caused by other deicers to quartzite, while the damage was significantly less for limestone aggregates. In case of asphalt concrete samples, it was found that conditioning asphalt samples using freeze-thaw cycles in the presence of a deicer solution caused a decrease in the indirect tensile strength and modulus of elasticity and an increase in the penetration values of the recovered asphalt cement. In addition, the test results showed that the maximum damage was caused by urea, while the damage due to the other deicers was comparable to that of distilled water.