The Influence of Aqueous Solution on Compacted Snow: A Field Investigation
Henri Giudici, Norwegian University of Science and Technology (NTNU)Show Abstract
Alex Klein-Paste, Norwegian University of Science and Technology (NTNU)
Johan Wåhlin, Statens vegvesen
Slippery road surfaces are a threat to traffic safety. This is particularly true in winter, where snow falling on roads forms a hard crust which is slippery and extremely difficult to remove. In order to prevent this hard crust formation, salt is applied to roads; indeed, in recent years more than 200,000 metric cubic tons of salt have been spread all over Norwegian roads. However, high salt amounts are both harmful to the environment as well as expensive, which is why optimizing salt applications has become a priority for transportation agencies in several countries. This study evaluates the effects of aqueous sodium chloride (NaCl) solution on compacted snow through completing a field investigation. A test car was driven on snow mixed with different amounts of aqueous NaCl solution (from 0 wt.% to 40 wt.%); this experimental run was then repeated approximately 20 times. A scraping test was also performed in order to evaluate the compacted salted snow’s strength. This study presents two main conclusions: an aqueous solution content of 10 wt.% keeps snow loose and thus easily removable from road traffic, while an aqueous solution of 5 wt.% weakens the snow substantially, allowing the snow mixture to be more easily plowed.
Friction and Snow–Pavement Bond After Salting and Plowing Permeable Friction Surfaces
Michelle Akin, Washington State UniversityShow Abstract
Laura Fay, Western Transportation Institute
Xianming Shi, Washington State University
Open-graded, ultrathin and permeable friction course surfaces (collectively referred to as PFSs) have been successfully used by many transportation agencies in several countries as a wearing surface to help reduce water splash and spray, reduce potential for hydroplaning, increase friction, and reduce noise. Despite their inherent advantages, when used in colder climates PFSs tend to freeze more rapidly, transport deicing/anti-icing chemicals from the road surface, clog from sands and other debris, and retain snow and ice for a longer period of time. Most of the reported difficulties with PFSs are at near-freezing temperatures (28–35°F). Laboratory tests were conducted using samples of traditional dense graded pavement (DGP), cores from new and old in-service open graded friction course pavements, and ultrathin friction course samples made from hot mix asphalt collected from paving operations. The tests were conducted in a walk-in environmental chamber at 28°F. Snow–pavement bond strength and static friction were measured to determine the effectiveness of anti-icing with salt brine and deicing with dry and prewet solid salt. The test results found that compacted snow bonds more strongly to PFSs, yet friction of PFSs was significantly greater than DGPs after snow removal, even without the use of salt. The PFSs appeared more white and snowy, and this appearance may be contributing to unnecessarily high application rates of salt by practitioners. Field testing is recommended to better understand the frictional behavior of PFSs during a variety of winter storm conditions and deicer application strategies.
Field Evaluation of Different Pre-Wetting Ratios for Sustainable Salting
Jaspreet Kaur, WSP CanadaShow Abstract
Taimur Usman, University of Waterloo
Liping Fu, University of Waterloo
This research presents the findings from a field study aimed at comparing the performance of different pre-wet ratios of salt for their impacts on snow melting performance/friction of road surfaces. The research was motivated by the question whether or not better snow melting performance can be achieved by using higher pre wetting ratios. Field tests were conducted on three sections of a provincial highway, located in Western Ontario in winter season 2016-2017 under three pre-wet ratios, i.e., 5% (current practice), 10% and 20%. Based on a comprehensive statistical analysis of the field testing data, it was found that salt pre-wetted at 20% improved friction levels by approximately 12% while reducing the salt usage by 19% and sand by 35% when compared to those at a pre-wet ratio of 5%. Examination of images collected during snow storms showed that sections treated with salts with higher pre-wet ratios generally had lower snow coverage.
Determining the True Cost of Making Brine and Comparing Liquid Deicers
Mallory Crow, University of AkronShow Abstract
William Schneider, University of Akron
Scott Lucas, Ohio Department of Transportation
Frank Phillips, The Ohio Department of Transportation
With the increasing cost of winter maintenance, agencies are constantly reviewing new ways to reduce cost while increasing or maintaining the level of service to the traveling public. One area of winter maintenance operation, which has been a focus to transportation agencies, is the various liquid deicers available on the market and the use of homemade brine solution. Despite all the research, there is a lack of information on how the cost of homemade brine is determined. This cost is necessary when comparing liquid deicers to one another, including brine. The cost analysis presented includes the raw material, capital cost of equipment, labor rate, and electric needed to make brine. Using a case study garage from ODOT, the true cost of brine is calculated to range between $0.13-0.17 per gallon. Since not all agencies will have the same inputs as the case study, a univariate sensitivity analysis was conducted to present the impact of each variable. This sensitivity analysis shows that the cost for salt and water have the greatest impact to the cost of brine. Some higher cost deicers may exceed the life of brine and therefore, may be justified in the extra cost per gallon. Therefore, in addition to the true cost of brine, a cost function model is developed to compare cost differences to performance of the deicers. These results will allow any two deicers to be compared based on cost and performance. These new guidelines will assist transportation agencies in determining the best liquid deicer operations.