Dilution Rate of Solid NaCl Anti-Icers Under Freezing Rain Conditions

The effectiveness duration of solid salt anti-icers will depend upon the pavement temperature, surface storage capacity, rainfall rate, and salt application rate. In order to better understand the likely dilution rate of solid salt under freezing rain conditions, Automated Surface Observing System (ASOS) weather data from 2018-2023 was analyzed for the U.S. cities of Minneapolis, Chicago, Cleveland, Indianapolis, Pittsburgh, and Louisville. Freezing rain events were defined as periods spanning 3 hours before the first indication of freezing rain or drizzle to 3 hours after the last indication. Analysis of precipitation rates during these periods indicated that the median rainfall rate in 5 of the 6 cities was 0.001 in/hr, that the 75th percentile rainfall rates were 0.01, 0.02, and 0.03 in/hr in 2, 3, and 1 of the cities, respectively, and the average rainfall rates ranged from 0.014 to 0.029 in/hr. Making the simplifying assumptions of ignoring salt loss due to traffic action and that salt will quickly and uniformly dissolve in surface moisture, a first approximation change in % NaCl, freezing point depression, and anti-icing effectiveness duration is calculated for typical freezing rain rates, surface storage capacities, and temperatures. At rainfall rates greater than 0.02 in/hr, solid salt may be diluted too quickly for practical anti-icing, but at many common rainfall rates, applying pre-wet or treated rock salt to dry pavement may be considered for anti-icing. The present study shows the importance of an understanding of pavement surface storage capacity for the prediction of anti-icer effectiveness longevity.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; Photos; References; Tables;
  • Pagination: 17p

Subject/Index Terms

Filing Info

  • Accession Number: 01907986
  • Record Type: Publication
  • Report/Paper Numbers: TRBAM-24-00680
  • Files: TRIS, TRB
  • Created Date: Feb 13 2024 4:35PM