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. Road salt pretreated with liquids is another option to take advantage of some of the benefits of liquids without an investment in new equipment. 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 only 23.3% salt). Many contractors are using liquids. If your organization has not tried liquids, consider trying them. Liquids provide 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. Sodium chloride, 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. Use of liquids in lower temperatures is not as common but 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 a liquid application directly followed by a solid application, often referred to as “shake and bake.”
Application rate guidance for anti-icing and DLA for light snow conditions (<1” per hour, <4” in 24 hours) and a variety of chemicals, products, and blends is documented in a Clear Roads research project (Clear Roads 2021). These rates are for roads (lane miles), but can be converted to gallons per 1000 square feet by dividing the rates by 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.
Liquids 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 gets slippery. Contractors that are experienced with liquid use may apply using fan nozzles. There is a learning curve to the use of liquids, experiment in a lesser-used area.
For anti-icing, liquids can be applied right before the storm to up to 48 hours before the storm. If applied too early, they may 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 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. Applying when a storm is predicted is the better approach.
Anti-icing Application Rate Guideline Table
| Conditions | CaCl2 or MgCl2 Gallons/1000 square feet | Salt Brine (NaCl) Gallons/1000 square feet |
|---|---|---|
| Regularly scheduled applications | 0.2 - 0.4 | 0.3 - 0.6 |
| Prior to frost or black ice event | 0.2 - 0.4 | 0.3 - 0.6 |
| Prior to light or moderate snow | 0.2 - 0.4 | 0.3 - 0.8 |
Caution: These are a starting point only. Adjust based on experience. Too high an application rate may result in slippery conditions or tracking. For other products, follow manufacturer's recommendations. (MPCA 2022)
Anti-icing is often done in combination with deicing if some snow or ice remains on the surface after mechanical removal efforts.
Direct Liquid Application
Direct liquid application rates are included in the Clear Roads chart linked above. DLA rates are generally higher than anti-icing rates, but lower than granular deicing rates. DLA is an advanced technique that requires training, proper equipment, and practice. It works well on frost or a very thin layer of ice. For compacted snow or ice, use stream nozzles with a high enough bar pressure to cut through the snow/ice and allow the liquid deicer to spread beneath and melt from the bottom up. If not applied properly and the liquid spreads on top of the ice, it can cause the ice to be extra slippery, similar to how a zamboni is used to treat a hockey rink surface.
Prewetting and Pretreating
Adding liquid deicers to coat granular deicers is known as prewetting or pretreating and is used to add deicers or additives to reduce bounce and scatter and/or improve cold temperature performance. Prewetting requires tanks, hoses, and nozzles on spreader vehicles to wet the material as it is applied at the spinner or auger. Another option that does not require new equipment is the use of pretreated materials. These can be purchased directly from vendors or made by mixing liquids into a stockpile.
For prewetting, 8-12 gallons of liquid is added per ton of dry material, most commonly 10 gallons per ton.
Application rates for prewet deicers are generally lower than for dry materials since more deicer sticks to the pavement. Rates vary depending on temperature and liquid type.
Prewet granular salt as it is being applied to the pavement to reduce bounce and scatter. This coats the deicers and can be used to add a liquid deicer that will be effective in lower temperatures.
Prewet abrasive materials to reduce bounce and scatter during application. Apply no more than 10 gallons of liquid per ton of abrasive. This amount helps embed the sand partially into packed snow and ice, improving traction. Excessive liquid application can cause the sand to melt through the snow or ice layer where it no longer provides effective traction.
Convincing Customers to Allow Use of Liquids
Customers that have not previously used liquids may be wary of their use and you may have to convince them to allow use of liquids on their site. The Property Manager version of this module will be useful to have them review or review with them, especially the information on the advantages of liquids that will benefit them, their facilities, and grounds.