Application Rates: Liquids
Use of liquids is a method to manage snow and ice using a sodium chloride brine or blend either before the storm (anti-icing, or sometimes referred to as pre-treatment) or during/after the storm (direct liquid application, DLA or post-treatment). Liquids can also be used to prewet the granular salt at the spinner or auger to help it stick to the road. Salt needs to be in solution to start the melting process. With liquids, the salt is already in solution so it works much faster and requires about one-fourth the amount of salt (because brine is 23.3% salt). Many contractors are using liquids. If your organization has not tried liquids, consider trying them or allowing your contractor to use them on your site. Liquids provides many benefits.
Liquid and granular comparison:
| Liquid | Granular |
|---|---|
Works faster | Works slower |
Less melting power | More melting power |
Uses less salt/chloride | Uses more salt/chloride |
Stays where you apply it- no bounce and scatter-less damage to vegetation | Dry material bounces and scatters and often ends up killing vegetation |
Lower cost after equipment investment | Higher cost due to more salt use and labor |
Effective as anti-icer to prevent bond | Won’t work as well as an anti-icing agent |
Can use to prewet granular salt | Prewet with liquids for faster melting |
Anti-icing can be done during normal work hours | Deicing may be required at any time of the day and may require overtime costs |
Liquids generally work in the same temperature ranges as granular materials, although they are often not recommended below 15°F. Brine can be used down to 15-20°F, but calcium and magnesium blends or some non-chloride products work better for temperatures between 15 to 20°F. Using liquids in lower temperatures is not as common, but it has been done down to as low as 0°F by public transportation agencies and knowledgeable contractors using magnesium blends with magnesium and calcium chlorides or organic additives, and brand name products. Another method used is a combination of liquid application directly followed by a solid application, often referred to as “shake and bake”. These application rates for light snow conditions (<1” per hour, <4” in 24 hours) and the above chemicals are documented in a Clear Roads research project (Clear Roads 2021). These rates are for roads, but can be converted to gallons per 1000 square feet by dividing the rates by the value 63.36. Be careful in warmer temperatures (>28°F) and high humidity, calcium and magnesium chlorides absorb moisture which may cause the pavement to get slippery.
Anti-icing and DLA chemicals are usually applied in lines using streamer/pencil nozzles as opposed to fan nozzles. The lines allow for areas of dry pavement between the wet areas that provide traction in case it does become slippery. Contractors very familiar with liquid use may apply using fan nozzles. There is a learning curve to the use of liquids, so try experimenting in a lesser-used area.
For anti-icing, liquids can be applied in the window 48 hours before the storm to right before it. If applied too early, the liquids may simply dust off with traffic. The anti-icing stripes will last for several days and are effective in preventing frost and ice buildup.
Application rates for liquids are listed in gallons/1000 square feet, gallons/acre or gallons/lane mile. The chart below is the MPCA’s Anti-icing application rate guidelines. Many others are available. If applying to driving lanes, you may want to use an application rate in gallons per lane mile. The guidelines below include rates for regularly scheduled applications (Condition 1). Applying when a storm is predicted is the better approach (Conditions 2 or 3).
Anti-icing is often done in combination with deicing if some snow or ice remains on the surface after mechanical removal efforts.