Pavement Temperatures and Effects: Pavement Temperature and Deicer Use
Deicers, including rock salt (sodium chloride), have a minimum practical melting temperature based on pavement temperature — not air temperature. This means that each deicer will melt snow and ice most effectively and efficiently at and above specific pavement temperatures. As pavement temperatures get colder, deicers become less effective. It is important to know the ingredients of the deicer being used and at what pavement temperatures it best performs. Some deicer products list a “eutectic temperature,” which is the lowest temperature they can melt ice under ideal, laboratory-type conditions — not what typically happens on your parking lot or sidewalk. Rock salt, for example, is effective down to about 15°F. Below 15°F, it will work very slowly and will not melt much ice, and below -6°F (the eutectic temperature), it will not work at all.
The practical or effective melting temperature is what is most useful. Once pavement temperatures fall below a deicers practical or effective melting temperature, it will not work well to melt snow and ice. It will be slow and will take much more product to get results. Choose a deicer that works at the current pavement temperature range, or use alternative materials, such as sand, to improve traction.
Common deicers for use on parking lots and sidewalks typically contain chloride in the form of either sodium chloride (NaCl), calcium chloride (CaCl2), magnesium chloride (MgCl2), potassium chloride (KCl), or various blends of these products. There are also non-chloride-based deicers like calcium magnesium acetate (CMA), potassium formate, and urea.
Sodium chloride is the most commonly used and lowest cost deicer, but its effectiveness drops sharply as pavement temperatures fall; one pound of salt melts far less ice and takes much longer to work at lower temperatures and becomes practically ineffective below 15°F. Each deicer has a different practical or effective melting temperature and environmental impacts, so it is important to use them selectively and sparingly.
Melt times for salt (NaCl) at different pavement temperatures
| Pavement Temp °F | 1 lb. of dry salt (NaCl) melts... | Melt time |
|---|---|---|
| 30 | 46.3 lbs. of ice | 5 min |
| 25 | 14.4 lbs. of ice | 10 min |
| 20 | 8.6 lbs. of ice | 20 min |
| 15 | 6.3 lbs. of ice | 1 hour |
| 10 | 4.9 lbs. of ice | Dry salt is ineffective and may blow away before it melts anything |
| 5 | 4.1 lbs. of ice | Dry salt is ineffective and may blow away before it melts anything |
When pavement temperatures drop below 15°F, switch to a deicer designed for cold conditions. Products such as magnesium chloride, calcium chloride, potassium formate, or blends of these materials with rock salt (sodium chloride) remain effective at lower temperatures and begin working more quickly. These deicers attract moisture from the air, helping initiate the melting process and improving performance when traditional rock salt becomes less effective.
Many deicing products are blends of ingredients or treated salt (rock salt treated with a liquid calcium or magnesium chloride or other additives). Sodium chloride is often the main ingredient because it is the least expensive. Unfortunately, there is no requirement that the manufacturer lists the amount of each ingredient, so you won’t know percent rock salt versus the more effective melters. Always check the ingredients and practical melting temperature listed on the deicer package so that you use the appropriate product for the conditions. If you hire contractors to do your work, ask what deicers they will be using on your property and if they measure pavement temperature to determine the appropriate deicer to use and application rates.
Lowest Practical Melting Temperature
Deicer | Lowest Practical Melting Temp. | Eutectic Temp. |
|---|---|---|
NaCl (Sodium Chloride) Delivered as rock salt, can be made into a brine. The basis of many bagged blends. Corrosive. Inexpensive. Readily available. | 15°F | -6°F |
MgCl2 (Magnesium Chloride) Form: liquid, pellets, flakes. Corrosive. Higher cost. Often found in blends with NaCl. | -10°F | -28°F |
CaCl2 (Calcium Chloride) Form: flakes, pellets, or liquid. Corrosive. Most effective ice melter at very cold temperatures. Higher cost. Often found in blends with NaCl. | -20°F | -60°F |
KCl (Potassium Chloride) Form: granular. Used in fertilizers. Often found in blends. | 25°F | 13°F |
CMA (Calcium Magnesium Acetate) Form: powder, crystals, pellets, or liquid. Non-corrosive to steel, biodegradable. Non-chloride. Higher cost. Often blended with NaCl. | 20°F | -18°F |
KHCO2 (Potassium formate) Form: liquid. Non-corrosive to steel, but corrosive to galvanized, biodegradable. Non-chloride. Higher cost. | -30°F | -76°F |
Blends Both chlorides and acetates exist in blends. Talk to the supplier to determine the lowest practical melting temperature. Most blends are mostly rock salt since it is the lowest cost material. | This depends on the blend. More calcium or magnesium chloride will lower practical melting temperature. | This depends on the blend. More calcium or magnesium chloride will lower practical melting temperature. |
Winter Sand/Abrasives Winter sand has 5-10% salt mixed in it to keep it from freezing. Abrasives should be used for cold temperatures when deicers are not effective. Minimize salt % in sand. | Never melts – provides traction only | Never melts – provides traction only |
If the pavement temperature is too cold for deicers, consider abrasive materials, like sand or grit, to provide traction. (This also avoids using chemicas). Remember to sweep up and reuse leftover sand or grit once the ice has melted. It has to be on top of the snow or ice to provide traction. Sweeping up extra abrasives also reduces tracking into the building.
Another option is to install heated pavement when replacing or constructing a sidewalk, parking lot, or entry area. Heated mats can also be used on existing surfaces to help keep pavement warm and prevent ice and snow buildup.