2013 Session: 204

• Wet Pavement Anti-icing: Proposed Physical Mechanism and Calculation for Minimum Application Rate
  Abstract: A commonly accepted mechanism for anti-icing of wet pavements is freezing point depression. However, not all aspects of anti-icing can satisfactorily be explained with the freezing point depression theory. In this study we tested the hypothesis that brine inclusions weaken the ice such that it does not withstand the loading from traffic. An experimental set-up was developed to freeze thin saline ice layers on pavement surfaces and test their resistance against simulated traffic load. It was found that the ice became too weak to withstand the imposed load when the combination of temperature and concentration resulted in an equilibrium brine fraction less than 0.3.The results from the lab experiments are compared with field measurements performed on wet roads in Norway. It shows that situations can occur where there is too little salt present to prevent freezing, jet traffic still goes as normal and the pavement was not experienced slippery. These measurements provide direct evidence that anti-icing of wet pavements is not solely based on freezing point depression. A new criterion, based on the equilibrium brine fraction, is proposed to determine the minimum amount of salt needed on pavement surfaces. This criterion predicts significantly lower amounts than predicted by the freezing curve. The notion of the weakening effect of anti-icing salts gives also an explanation why a certain amount of traffic is needed on pavements to achieve an effective anti-icing operation.
  Authors: Klein Paste, Alex
  Authors: Klein Paste, Alex
  Year: 2013
  Document Type: Paper
  Subject: Maintenance and Preservation; Safety and Human Factors
  Session: 204
  Paper Number: 13-0547
• Effect of Common Deicing Chemicals on Ice-Bond Formation in Compacted Snow
  Abstract: Application of chemicals during snowfall in order to to keep the snow plowable is a common road maintenance practice to ensure regularity and improve traffic safety during winter. However use of chemicals has adverse effects on environment and structures. In order to optimize chemical usage for anti-compaction measures, more knowledge is needed on the mechanism behind it. Earlier studies have shown that the presence of a sodium chloride (NaCl) solution in snow reduces the strength of the bonds that form between grains when snow is compressed, and thereby decreases the hardness of compacted snow. It is however not clear whether this is an effect of the introduction of liquid water into the snow or if it is an effect of the solutes present in the solution. By measuring the hardness of compressed snow saturated with solutions of six common deicers, it was shown that the solutes do have an effect on the inter-particle bonds in snow. By comparing the effect of potassium formate (KCOOH) with NaCl solution on snow containing between 5-50 w% solution it becomes clear that the effect of the solutes can be substantial. To achieve the same snow hardness, only half the amount of KCOOH solution was needed compared to the NaCl solution.
  Authors: Wåhlin, Johan; Klein Paste, Alex
  Authors: Wåhlin, Johan; Klein Paste, Alex
  Year: 2013
  Document Type: Paper
  Subject: Maintenance and Preservation; Safety and Human Factors
  Session: 204
  Paper Number: 13-2508
• Water Spray Endurance Test Investigation: Evaluation of Highway Anti-icer Performance Under Freezing Precipitation
  Abstract: A modified Water Spray Endurance Test (WSET) was adapted from the SAE Standard AS5901B and used to study the anti-icing endurance of a variety of sodium chloride-based highway anti-icer liquids. Freezing precipitation immediately forms rime ice on surfaces with no anti-icer treatment. On surfaces treated with anti-icer, freezing precipitation goes through a series of stages, initially forming a liquid brine layer, then forming non-adherent glaze ice, and finally forming rime ice. The modified WSET test was used to study the effect of a variety of additives in NaCl anti-icing liquids. High molecular weight organic polymer additives were found to strongly inhibit the onset of rime ice formation. The delay in the onset of rime ice formation caused by anti-icers is postulated to be due to an enhancement of surface melting, increasing the size of the quasi-liquid layer at the ice surface and favoring glaze rather than rime ice formation until the anti-icer has been sufficiently diluted. The same surface melting enhancement caused by anti-icer chemicals may also be responsible for the observed effectiveness of low concentrations of anti-icer at preventing ice adhesion to pavement surfaces. In this context, the use of the modified WSET test to evaluate rime ice growth rates is discussed as a possible way to compare the relative precipitation resistance (and therefore “effective lifetime”) of different anti-icer formulas.
  Authors: Koefod, Scott
  Authors: Koefod, Scott
  Year: 2013
  Document Type: Paper
  Subject: Maintenance and Preservation; Safety and Human Factors
  Session: 204
  Paper Number: 13-0517
  Practice-Ready: Yes
• Accuracy of SOBO-20 in Measurement of Salt on Winter Pavements
  Abstract: The use of chemicals is essential in snow and ice control operations. Sodium chloride (salt) is normally used, as it is efficient, widely available and rather inexpensive. However it is harmful for the environment if encountered in too great quantities, and there is nowadays a great attention placed upon the importance of reducing the usage of salt, while still maintaining road serviceability and safety.Optimizing the use of salt requires to accurately knowing how much salt is on the pavement surface. Unfortunately, there is currently no well-documented method available to determine this quantity. SOBO-20 is one of the most common instruments used by the winter maintenance community to calculate salt amounts, although the reliability of the instrument has not been shown yet. The present work aims to fill this gap by carrying out measurements on brine (dissolved salt), dry salt particles and re-crystallized salt. The presented results support the conclusion that SOBO-20 is an accurate and reliable instrument for measuring brine on asphalt pavements. However, it largely underestimates the amount of dry or re-crystallized salt, and much attention should be paid when using SOBO-20 on dry pavements. Compliance with the manufacturer's recommendations regarding the proportion of acetone in the measuring fluid is also essential for accurate salt readings. These results on the instrument performance should lead to a better understanding of the salt distribution and action time.
  Authors: Lysbakken, Kai Rune; Lalagüe, Anne
  Authors: Lysbakken, Kai Rune; Lalagüe, Anne
  Year: 2013
  Document Type: Paper
  Subject: Maintenance and Preservation; Safety and Human Factors
  Session: 204
  Paper Number: 13-2606
  Practice-Ready: Yes
• Water Spray Endurance Test Investigation: Evaluation of Highway Anti-icer Performance Under Freezing Precipitation
  Authors: Koefod, Scott
  Authors: Koefod, Scott
  Year: 2013
  Document Type: Presentation
  Subject: Maintenance and Preservation; Safety and Human Factors
  Session: 204
  Paper Number: 13-0517
• Wet Pavement Anti-icing: Proposed Physical Mechanism and Calculation for Minimum Application Rate
  Authors: Klein Paste, Alex
  Authors: Klein Paste, Alex
  Year: 2013
  Document Type: Presentation
  Subject: Maintenance and Preservation; Safety and Human Factors
  Session: 204
  Paper Number: 13-0547
• Accuracy of SOBO-20 in Measurement of Salt on Winter Pavements
  Authors: Lalagüe, Anne
  Authors: Lalagüe, Anne
  Year: 2013
  Document Type: Presentation
  Subject: Maintenance and Preservation; Safety and Human Factors
  Session: 204
  Paper Number: 13-2606
• Effect of Common Deicing Chemicals on Ice-Bond Formation in Compacted Snow
  Authors: Klein Paste, Alex
  Authors: Klein Paste, Alex
  Year: 2013
  Document Type: Presentation
  Subject: Maintenance and Preservation; Safety and Human Factors
  Session: 204
  Paper Number: 13-2508