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Best Practices for Road Weather Management Version 2.0

Best Practices > Publications > Publication Titles

Title:

Evaluation of ODOT Roadway/Weather Sensor Systems for Snow and Ice Removal Operations Part III: Optimization of Salt Brine Pre-Treatment Application Rates and Frequency

Abstract:

The Ohio Department of Transportation (ODOT) has initiated pretreatment as an integral part of a winter management strategy. Currently forty gallons per lane mile of 23% salt brine (NaCl) by weight is applied at a minimum frequency of two times per week when conditions warrant. In order for ODOT to develop the most effective plan for pretreatment, an in-situ study to provide data on decay of brine on trafficked pavement was needed. Objectives included a survey of other state DOT's pretreatment protocols, laboratory studies to discern brine concentrations that precluded ice formation, brine decay with traffic and time on several pavements, and correlation of laboratory and field data. Ten of the 28 state DOTs responding to the survey regarding pretreatment protocol applied NaCl two to 24 hours prior to a storm; two states used surface type, traffic volume, and air temperatures for decision making. The survey reinforced the need of laboratory and field studies. In the laboratory, release temperatures of the ice/surface bond at various brine concentrations were obtained utilizing conductivity and physical observation techniques. Laboratory tests with the field brine measurement instrumentation (SOBO-20 by Boschung Megatronic AG) provided correction factors for the field data on AC and PCC pavements. Sodium chloride brine was applied and measured in-situ in mass per area at five field sites (ATH-50 PCC, ATH-50 AC, DEL-23 PCC, DEL-23 AC, and ATH-33 AC) encompassing at least four sections at each site. Initial losses and decay due to time/traffic were obtained. Of the five test sites, AC (micro seal), AC (NOVA chip), and a transversely grooved PCC pavement provided statistically valid data to develop residual decay equations as a function of time/traffic. Field decay of brine was incorporated into laboratory brine/ice/specimen bonding temperature findings to determine the effective ice prevention temperatures as a function of time/traffic for AC and PCC at standard application rates.

Source(s):

Ohio University Department of Civil Engineering and the Ohio Research Institute for Transportation and the Environment, prepared for the Ohio DOT

Date: 2003

Author:

Mitchell, Hunt, Richardson

Keywords:


Anti-icing/deicing
Volume
Air temperature
Pavement condition
Winter maintenance

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