Using ice and snow melting compounds to clear snow and ice from walks, drives, and entries near buildings is virtually a universal practice today. With the recent legal decisions that put the onus on a property owner for acts of nature, clearing snow or ice from your driveway, walks and stairs is more important than ever, unless you enjoy the prospects of a lawsuit. Facility maintenance personnel learned long ago that to achieve safe surfaces in the shortest time with the least total cost, ice melters are a necessity.
Few Actual Materials
Although there are many brands of ice and snow melter, the list of materials in common use is much shorter. 95% of chemical ice melters on the market are made from one or more of these basic ingredients:
- Sodium Chloride (rock salt)
- Calcium Chloride
- Potassium Chloride
- Magnesium Chloride
- Sodium Acetate
- Calcium Magnesium Acetate
- Ammonium Nitrate
- Ammonium Sulfate
- Various blends of the above, with and without abrasives (such as sand, etc.)
Rock salt and calcium chloride are most extensively used. Rock salt, calcium chloride, potassium chloride, and magnesium chloride are naturally occurring salts. Urea, ammonium nitrate, and ammonium sulfate are synthetic materials which find their most common applications as fertilizers.
How Ice and Snow Melters Work
Generally, all ice and snow melters work in the same way. They depress the freezing point of ice or snow and turn the mixture into a liquid or semi-liquid slush.
Solid chemical salts bore through ice or snow and form a strong brine solution. This brine spreads under the ice or hard-packed snow and breaks the bond to the surface. Once loose, the ice or snow is easily removed by plowing or shoveling. In many cases, users apply the material in anticipation of ice or snow to prevent the bond to the surface and melts the snow or ice as it comes in contact with the brine.
Fertilizer products work in much the same manner, though they do not form a brine. All are water soluble and the resulting solution acts by depressing the freezing point of snow and ice, turning it back to a liquid.
Comparing Temperature Ranges
The first measure of an ice melters effectiveness is the range of temperatures in which it can provide deicing action (in a reasonable time period). The lowest temperature limits for these materials is defined as effective within 15-20 minutes of application. A listing of deicing materials based on their effective temperature ranges is as follows:
- Calcium Chloride (-25 F)
- Magnesium Chloride (5 F)
- Sodium Acetate (5 F)
- Calcium Magnesium Acetate (CMA) (5F)
- Potassium Chloride (12 F)
- Urea (15 F)
- Rock Salt (22 F)
Rock salt is the most commonly used ice melter. It is inexpensive and melts ice. Compared to other materials, though, it has limited effectiveness in very cold temperatures. It will not melt ice at temperatures below 22 degrees.
Potassium chloride and urea are common fertilizers that are often perceived as safe products to use around vegetation. Urea does not contain chlorides, so it’s less corrosive and safer for use on concrete containing rebar and around steel structures.
Sodium acetate and CMA is a dry formulation used as an ice melter on bridges, parking decks and other concrete surfaces. It does not attack rebar in reinforced concrete and is biodegradable. It changes ice and snow into a oatmeal texture which is not desirable for walkways. It may be cost-prohibitive, as typically costs four to five times more than calcium chloride.
Magnesium chloride is very similar to calcium chloride. The major drawback to magnesium chloride is that it is only 48% active and needs to be applied at a greater rate than calcium chloride.
Calcium chloride is a liquid brine in its natural state and is converted into a dry material by removing the water. It quickly absorbs moisture from the atmosphere. When converted into a liquid, calcium chloride gives off heat and will melt ice at temperatures of -25 degrees.
In order for an ice melter to be effective, it must become soluble quickly. It is the soluble solution, not the solid material, that penetrates the ice or snow to provide the undercutting. There are basic differences in how quickly different compounds turn into a deicing brine at low temperatures.
Calcium chloride and magnesium chloride are liquids in their natural states and love to return to a liquid. Additionally, When the solid form of these compounds come into contact with water, they release heat. In practice, once calcium chloride and magnesium chloride touch ice or snow, they immediately pick up water to form a strong brine, emit heat to give added deicing effect, create more water, and form more brine. This process is repeated over and over.
Rock salt and potassium chloride are both solids in their natural state. When they come into contact with moisture, they also will go into solution to form a strong brine. But, in doing so, they must absorb heat from the environment.
Urea, ammonium nitrate, and ammonium sulfate also go into a solution (though not a brine) when they contact moisture, but also must absorb heat before the solution can be formed.
Another measure of ice melter effectiveness is the amount of material needed to accomplish the undercutting job. Perhaps the best way to compare materials is to look at the volume of ice they are able to melt pound-for-pound under normal temperature conditions over a reasonable time period. In most applications, the three most effective deicers are calcium chloride first, followed by magnesium chloride and rock salt.
A final measure of performance for an ice melter is how long it will provide deicing action. The longer the ice or snow melter acts, the less reapplication is needed. The natural state of the deicer (discussed above) has the greatest effect on how long an ice melter will last. Those which are naturally liquids – calcium chloride and magnesium chloride – last longer since they resist evaporation.
The shape of ice melters is also important. Research has found that rounder particles have distinct performance advantages. Round particles contact a smaller surface area than flakes or irregularly shaped granules, making them more effective at moving down through the ice or snow, rather than horizontally across it. This results in faster penetration to the pavement and quicker breaking up of the snow or ice.
Given the alternative of hazardous conditions (and potential lawsuits!), the benefits of ice or snow melters far outweigh their potential disadvantages. However, the other concerns of using these products should be addressed.
Pets – Some ice and snow melting are not Pet Safe. If you have an area that your pets will be using often, you should look for an ice and snow melter that is labeled as being Pet Safe or Pet Friendly.
Residues – the only materials which have the potential for leaving a solid residue on internal flooring are sodium chloride and potassium chloride
Effect on Vegetation – All de-icing materials have the potential to damage plant life. In the amounts typically used for grounds maintenance, the threat to grass, trees and shrubs is minimal. Be aware that over application can damage vegetation.
Effect on Concrete – Many are concerned with deicers effects on concrete. Of the deicer’s listed, only ammonium sulfate and ammonium nitrate will chemically attack concrete. The others do not chemically attack concrete, but can affect the freezing point of water, which will increase freeze-thaw cycles the water goes through which can cause the expansion of freezing water and ultimately exceed the strength limits of the concrete, resulting in spalling of the concrete. Proper use of deicers will minimize concrete damage along with prompt removal of slush and residual deicer material will minimize the chance for damage to concrete from freeze/thaw cycles. (By the way, these freeze/thaw cycles are what cause potholes in the road during the winter when water seeps in cracks in the pavement then freezes underneath, causing the pavement to break up from the pressure of the ice.)
Some ice melters can damage concrete containing rebar. When chlorides in the brine seep into the concrete and come in contact with the rebar, corrosion begins, resulting in concrete cracking and spalling. For this reason, chlorides are not recommended for use on concrete containing rebar or around steel structures.
Our staff is here to help you select the de-icer that is best for your application. Please feel free to ask for our help.
We recommend using your ice and snow melter before the snow begins. This will help melt snow as it falls and will also prevent it from bonding to the walk or driveway.
Wear gloves when using any de-icer.
You can make spreading your ice and snow melter easier by using either a walk behind or handheld fertilizer spreader. Just be sure wash it out well after each use.
Since many of the ice melting products love moisture, be sure to store them off the floor and preferable in a sealed bag or bucket.
Don’t forget to spread some traction sand as well. It will help people get their footing when there is ice or snow on the ground.