|Deicers work by lowering the freeze point of water. There are many factors to be considered when choosing a deicer, one of the most important factors is the pavement temperature and pavement temperature trend. For example, Rock salt can melt to -6 oF pavement temperatures but the colder the pavement the slower it works. A best practice is to avoid using dry rock salt at pavement temperatures below 15 oF because it is too slow. The most common approach to speed up the melting processes is to add a liquid deicer to your granular product or use straight liquids (DLA - Direct Liquid Application). Liquids are much faster acting than granular products. They type and gradation of your granular product also will influence the speed of melting. If you commonly have salt left on dry pavement after the snow is gone it is time to revisit your strategies. One easy step is to attend the smart salting training classes where you will learn more about deicer selection and application rates. Link to smart salting training calendar. For a comparison of different deicers, see this table|
Winter weather conditions in Minnesota can cause icy roads and walkways, leading to dangerous conditions for drivers and pedestrians. In order to combat this situation, municipalities, businesses, and individuals often employ the use of deicers. A deicer is a substance that melts or prevents the formation of ice, and does so by lowering the freezing point of water and preventing a bond between ice and paved surfaces. A study by Marquette University found that deicing roads with salt reduces accidents by 88 percent and injuries by 85 percent (Kuemmel and Hanbali, 1992).
While deicers have the ability to greatly improve road and walkway safety, they can also have negative effects on the environment and surrounding infrastructure. Once applied, deicers move with melt water to our surface and groundwater. In addition, some deicers are corrosive and will negatively impact roads, bridges, and other structures, as well as automobiles. Efforts are underway to minimize these environmental and infrastructure impacts, including optimizing deicer application and using of alternative deicing chemicals. Despite these negative effects, the benefits of deicers to public safety ensures they will be utilized for years to come.
The Iowa Department of Transportation prepared a winter maintenance training series that includes a video titled How Deicing Chemicals Work.
A list of the chemicals approved for use in deicing by the Minnesota Department of Transportation (MnDOT) can be found here. Link here for a discussion on environmental impacts of deicers and deicing additives.
The chloride-based deicers discussed in this section are sodium chloride (NaCl), magnesium chloride (MgCl2), and calcium chloride (CaCl2). In general, chloride-based deicers are the least expensive and most used deicers on the market.
Acetate-based deicers are often used in areas where the use of chloride-based deicers is limited. Acetate-based deicers include calcium-magnesium acetate (CMA), potassium acetate (KAc), and sodium acetate (NaAc). Much of the information provided here is based on studies and experiences using CMA.
Advantages of acetates include the following.
Disadvantages of acetates include the following.
Acetates include the following.
Other deicer options include free or low-cost cheese brine, pickle juice or other industry by-products on your surfaces for anti-icing or deicing. However, these should not be used without taking appropriate steps. Steps to take before using a waste stream product include but are not limited to the following .
Carbohydrate are an additive to deicers and are an agricultural product often made from the fermentation of grains or the processing of sugars such as cane or beet sugar (Rubin et al., 2010). Small quantities of carbohydrates are sometimes used with other deicers.
There are pros and cons about blending an agricultural additive into your brine or rock salt. Alone, carbohydrates do not aid in melting ice or snow. Agricultural products may have short term negative environmental impacts, including noticeable algal blooms or fish kills. However, mixed into chloride products, they have the potential to reduce deicer application rates and increase deicer performance for a variety of situations. The most common positive aspects of these additives include the following (Fortin et al, 2014; Rhodan and Sanburn, 2014).
For information on this topic, see Understanding the Effectiveness of Non-Chloride Liquid Agricultural By-Products and Solid Complex Chloride/Mineral Products at the ClearRoads website.
|Category||Type||Lowest Practical Melting Pavement Temperature 1,2||Potential for corrosion impairment3||Environmental Impact3|
|Atmospheric Corrosion to Metals||Concrete Matrix||Concrete Reinforcing||Water Quality/Aquatic Live||Air Quality||Soils||Vegetation|
|Chloride Based Deicers||Sodium Chloride||15°F||High; will initiate and accelerate corrosion||Low/moderate; Will exacerbate scaling; low risk of paste attack||High: Will initiate corrosion of rebar||Moderate: Excessive chloride loading/metals contaminants; ferrocyanide additives||Low: Leads to reduced abrasives use||Moderate/High: Sodium accumulation breaks down soil structure and decreases permeability and soil stability; potential for metals to mobilize||High: Spray causes foliage damage; osmotic stress harms roots, chloride toxicosis|
|Calcium Chloride||-20°F||High; Will initiate and accelerate corrosion; higher potential for corrosion related to hydroscopic properties||Low/moderate; Will exacerbate scaling; low risk of paste attack||High: Will initiate corrosion of rebar||Moderate: Excessive chloride loading; heavy metal contamination||Low: Leads to reduced abrasives use||Low/Moderate: Improves soil structure; increases permeability; potential for metals to mobilize||High: Spray causes foliage damage; osmotic stress harms roots, chloride toxicosis|
|Magnesium Chloride||-10°F||High; Will initiate and accelerate corrosion; higher potential for corrosion related to hydroscopic properties||Moderate/high: Will exacerbate scaling; risk of paste deterioration from magnesium||High: Will initiate corrosion of rebar, evidence suggest MgCl2 has the highest potential for corrosion of chloride produces||Moderate: Excessive chloride loading; heavy metal contamination||Low: Leads to reduced abrasives||Low/Moderate: Improves soil structure; increases permeability; potential for metals to mobilize||High: Spray causes foliage damage; osmotic stress harms roots, chloride toxicosis|
|Acetate Based Deicers||Calcium Magnesium Acetate||20°F||Low/moderate; Potential to initiate and accelerate corrosion due to elevated conductivity||Moderate/high: Will exacerbate scaling; risk of pate deterioration from magnesium reactions||Low; probably little or no effect||High: Organic content leading to oxygen demand||Low: Leads to reduced abrasives use||Low/Moderate: Improves soil structure; increases permeability; potential for metals to mobilize||Low: Little or no adverse effect; osmotic stress at high levels|
|Potassium Acetate||-15°F||Low/moderate; Potential to initiate and accelerate corrosion due to elevated conductivity||Low; probably little or no effect||High: Organic content leading to oxygen demand||Low: Leads to reduced abrasives use|
|Carbohydrates||Beet Juice||NA||Low; Potential to initiate and accelerate corrosion due to elevated conductivity clams of mitigation of corrosion require further evaluation||Low; Probably little or no effect||Low; Probably little or no effect; claims of mitigation of corrosion require further evaluation||High Organic matter leading to oxygen demand; nutrient enrichment by phosphorus and nitrogen; heavy metals||Low: Leads to reduced abrasive use||Low: Probably little or no effect; limited information available||Low: Probably little or no effect|