Pavement Temperatures and Effects: Pavement Temperature and Deicer Use
Deicers (also known as ice melt), 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 to what pavement temperature it best performs. 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. 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 driveway or sidewalk.
Whether or not a deicer is marketed as 'environmentally friendly', minimizing use is always your best bet.
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.
- Deicing at home
- Table: Melt times for salt
- Table: Lowest practical melting temperature
- Too cold for salt?
Common deicers for home use on sidewalks and driveways typically contain chloride in the form of either sodium chloride (NaCl), calcium chloride (CaCl2), magnesium chloride (MgCl2), 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 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. (See module 1).
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 |
Use other deicers when pavement temperatures fall below 15°F. Magnesium chloride, calcium chloride, and potassium formate work in colder temperatures and work faster because they absorb moisture from the air, jumpstarting the melting process.
The table in the next tab, "Lowest practical melting temperature", highlights common deicer ingredients, information about the deicer, and lowest practical melting temperatures and eutectic temperatures.
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.
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 any of the deicers you have on hand, or to avoid use of chemicals, consider an alternative. Use sand or grit to provide traction, and remember to sweep up and reuse leftover sand or grit once the ice has melted. One less common option would be to install heated pavement with a new sidewalk or driveway or use heated mats to keep the pavement warm and prevent ice and snow build-up.