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12 are numerous applications of mixtures containing smaller with the (excessive) use of abrasives just as there are poten- amounts of chemicals, or unless there are very high applica- tial environmental impacts associated with the (excessive) tion rates of mixes containing smaller amount of chemicals. use of chemicals in deicing operations. Winter maintenance This strategy is a viable option for unpaved roads if there is field personnel, as stewards of the highway and its environ- no, or very little, ice control chemical in the mixture. ment, must be ever vigilant in resisting the temptation to use more snow and ice control materials than are needed for the operational conditions. MECHANICAL REMOVAL ALONE Mechanical removal alone is a strategy that involves the COMBINATIONS OF STRATEGIES physical process of attempting to remove an accumulation of snow or ice by means such as plowing, brooming, or blow- Combinations of strategies are almost always used. Many ing without the use of snow and ice control chemicals. This winter weather events present a variety of weather and pave- strategy is strictly a physical process. ment conditions. To deal effectively with these changes, This strategy is suitable for use in a variety of situations. It strategies and tactics need to be adapted. The most common may be the only treatment rendered on unpaved or very low scenario requiring changes is when pavement temperatures LOS roads. On higher LOS roads, it is effective when pave- fall to a low level during a winter weather event. As ice con- ment temperatures are above freezing and snow is not bond- trol chemicals become much less effective in colder temper- ing to the pavement. Similarly, when pavement temperatures atures, agencies often switch from straight chemical treat- are lower than about 12F and snow is not bonding to the ments to treatment with abrasives or mixtures of abrasives pavement, this is an effective treatment. This also may be the and chemicals. final treatment for a winter weather event after ice control Achieving stated LOS goals may require using different chemicals or warming pavement temperatures have loosened strategies and tactics during a single winter weather event. any bonded snow or ice from the pavement. An example is where an agency wants a low within-winter weather event LOS and a high LOS at or after the end of a winter weather event. In this case, an agency may initially do TRACTION ENHANCEMENT anti-icing with ice control chemical, use only mechanical removal techniques during the event, and utilize deicing at There are some techniques for enhancing the traction of the end of the event. The early anti-icing treatment makes the snow/ice surfaces. Mechanical roughening, grooving, or tex- later deicing treatment more effective. turing provides a small level of traction and directional sta- bility enhancement. This technique is not suitable for higher volume roads as the effect is short lived. It may provide an SUMMARY option in environmentally sensitive areas with low traffic volume. Higher LOS can only be provided if snow/ice is not bonded The most common technique for enhancing friction on a to the pavement. There are only two mechanisms that will snow/ice surface is to apply abrasive materials such as sand, achieve this: (1) the use of ice control chemicals and (2) favor- cinders, ash, tailings, and crushed stone/rock. These materials able pavement temperatures. Using the right amount of chem- may be applied straight or with varying amounts of ice con- ical for the operational, weather, and pavement conditions trol chemical in a mixture. This is thought to make them is the most efficient and effective way to meet most higher "adhere" a little better to the surface and last a little longer. A LOS goals. solid form of ice control chemical may be mixed into the abra- Warm pavement temperatures above 32F will usually sive stockpile and allowed to age (to form a brine and coat not allow light to moderate rates of precipitation to bond. some of the abrasive particles). A liquid chemical may be Very cold pavement temperatures, lower than about 12F, sprayed onto the abrasives while they are being applied to the together with dry or powder snow will usually not produce road or while the stockpile is being created. Another tech- ice/pavement bond. In either case, mechanical removal alone nique for enhancing the "retention" and longevity properties may be all that is necessary to achieve a high LOS. is to spray the abrasives with warm water as they are being There is always the potential danger of chemical residuals dispensed onto the road. This is reported to be quite effective. becoming diluted and resulting in a refreeze condition, whether Traction enhancement's primary role is limited to lower at elevated or low temperatures. The material treatment design volume roads, situations where ice control chemicals will process which follows considers the impact of weather and not likely "work," and in environmentally sensitive situa- road conditions that occur after a given treatment and before tions where the use of ice control chemicals must be lim- the next scheduled treatment in order to prevent refreezing of ited. There are potential environmental impacts associated chemical solutions.