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Melting Ice - Roadways
Responsible use of calcium chloride can improve the effectiveness of road and highway ice control programs used to keep roads open and safe. Best practices should be followed including using the minimum amounts of calcium chloride necessary to achieve desired results and avoid over-application.
LIQUIDOW® solution alone, in enhanced liquid blends, or salt prewetted with LIQUIDOW®, may be used for anti-icing. Before deciding which to use, consider equipment availability, pavement temperatures, and current and expected weather conditions.
Compared to deicing after weather events, anti-icing requires considerably smaller amounts of ice melter material, reducing material and application costs, as well as potential runoff to the environment.
Anti-Icing application rate should be tailored to the type of weather event expected, pavement temperature, and your experience. Two sets of guidelines, detailed in the table below, can serve as initial reference points. These are based on the equivalent quantity of dry solids applied at the specified temperatures.1,2
Typical Chemical Application Rates for Anti-icing Activities at 15°F to 32°F (-10°C to 0°C) |
||||
|
Reference |
Light icing |
Light snow |
Heavy snow |
Freezing rain |
| "Manual of Practice for Effective Anti-Icing Program" FHWA/CRREL |
7-36 (25-130) |
28-55 (100-200) |
28-55 (100-200) |
21-110 (75-400) |
| "Manual of Practice for Anti-Icing of Local Roads" New Hampshire T2 |
18-36 (65-130) |
28-55 (100-200) |
28-55 (100-200) |
21-110 (75-400) |
Typical Chemical Application Rates for Anti-icing Activities at 15°F to 32°F (-10°C to 0°C)
"Manual of Practice for Effective Anti-Icing Program" FHWA/CRREL
Light icing
7-36
(25-130)
Light snow
28-55
(100-200)
Heavy snow
28-55
(100-200)
Freezing rain
21-110
(75-400)
"Manual of Practice for Anti-Icing of Local Roads" New Hampshire T2
Light icing
18-36
(65-130)
Light snow
28-55
(100-200)
Heavy snow
28-55
(100-200)
Freezing rain
21-110
(75-400)
1Transportation Research Board, National Cooperative Highway Research Program (NCHRP), Report 577, 2007
2Dry Chemical spread rate, kg/lane-km (lb/lane-mi)
Apply LIQUIDOW® solution at a rate of 6-10 gallons per ton (25-42 liters per metric tonne) of rock salt. This liquid prewetting rate can be optimized by local agencies based on experience and storm conditions. Agencies are then able to minimize prewetted salt applications based on conditions.
Prewetted abrasives embed more securely in packed snow and ice, reducing losses from bounce and scatter, which helps ensure maximum traction improvement.
Apply LIQUIDOW® solution at an application rate typically lower than rates used to prewet rock salt depending on the composition of the materials. As with pre-wetting rock salt, the liquid application rate will vary based on local experience and storm conditions.
For conventional post-storm deicing operations, DOWFLAKE® Xtra Calcium Chloride Flakes may be blended with rock salt to provide faster melting action at lower temperatures than rock salt alone. Look to have at least 20% calcium chloride content to see an appreciable increase in performance over rock salt alone.
Dry calcium chloride/rock salt blends are useful at especially low temperatures and on critical road sections such as bridges, highway ramps, and sharp turns or grades because it can significantly reduce the time required to break the bond between ice and pavement. As the graph shows, this can be an enormous advantage when it is necessary to restore traction in hazardous areas, particularly at temperatures below 15°F.
Time Required to Break Ice Bond by Penetrations of Chemical to Surface of Road 1
Rate: 500 lbs/lane mile on solid, glare ice
1Public Works magazine, August 1978, "Enhancing the ice melting action of rock salt."
On-site blending of custom brine formulations is a practice that has gained popularity among highway departments and commercial applicators. These brine solutions are most often mixes of sodium chloride, calcium chloride or magnesium chloride, and sometimes corrosion inhibitors, anti-foaming agents, and pavement adhesion/viscosity additives. They can be used for deicing, salt prewetting or anti-icing applications. Calcium chloride is commonly used in brine blends to lower the effective working temperature of the blend.
A good example is the precision brine mixing system used by the McHenry County Division of Transportation in northern Illinois. The system includes specially designed equipment for storage, brine production, blending, and high-speed loading onto vehicles. It provides fully automated, highly accurate blending of mixes that provide more predictable and consistent on-road results. McHenry County uses the system to produce a number of different brine blends for deicing, prewetting and anti-icing. One blend used extensively by the county consists of 80% salt brine, 10% calcium chloride, and 10% sugar beet by-product. McHenry County reports effective performance for this blend at pavement temperatures “at or below two degrees Fahrenheit”.1
In addition, the Ohio Department of Transportation uses automated brine production systems extensively. Some of the counties add up to 10% calcium chloride to their brine mixes.2
1“Blending Liquid Deicing Chemicals Precisely”, R.M. DeVries, APWA Reporter, 2005.
2“Ohio Department of Transportation Snow & Ice Practices,” Ohio Department of Transportation Division of Operations Office of Maintenance Administration.