Time Dependent Release of Salts From Asphalt Pavement Containing Anti-Icer Additives

Abstract

A laboratory investigation of anti-icing asphalt pavement (AIAP) containing salt storage additives (SSA) was carried out to explore the effect of pavement thickness, asphalt performance grade, and chloride salt composition on the salt release behavior through simulated precipitation wash cycle tests. The mass of salt release across repeated wash cycles over up to 2 years was quantified analytically and compared with typical NaCl brine anti-icing application rates. Consistent with previous studies, after an initial high release of salt, AIAP was found to settle into a roughly steady though gradually decreasing salt release over time and show a gradually increasing “regeneration” time required between precipitation events to recover to an effective anti-icing salt level at the surface. Given sufficient recovery time, the AIAP samples in these tests were able to release salt equivalent to 20 gal/lane mile of NaCl brine for an extended period. Pavement thickness between 0.625 and 1.25 in. and choice of asphalt binder performance grade between 58-28 and 64-22 were found to have little or no effect on the salt release behavior of AIAP, suggesting that adopters may exercise flexibility as needed within these ranges. The ratio of CaCl2 to NaCl in the SSA also had little or no effect on AIAP salt release behavior, indicating that formulators can focus on other potential performance functions for CaCl2.