There is a lot of general information out there about salt use for snow and ice management. We wanted to take a minute to explain it in simple terms. We hope that this guide provides enough detail but is conveyed in a simple fashion that answers any questions you may have about using salt on your driveway or walkways this winter.
Although there are many chemical options for treating ice and snow, there really are only two major chemicals used today. Sodium Chloride, or road/rock salt, and calcium chloride, sometimes called chloride pellets. Rock salt dominates the market. It is cheap, abundant, and spreads easily.
All salts do the same basic thing. They lower the temperature at which water freezes. Instead of the traditional 32 degrees(0 degrees Celsius), a 10% saltwater solution will freeze at about 20 degrees. A 20% solution freezes at about 2 degrees. If you know much about salting, you know that rock salt is generally only said to be effective down to about 15 degrees. This is true. Although dissolved rock salt in a heavy solution can keep water from freezing well below 15 degrees, it is not able to dissolve readily into existing ice and snow at temperatures below 15 degrees. This means other options should be considered when the temperatures begin to fall.
There are some factors that can cause rock salt to be more effective and worth spreading. Mixing rock salt with another salt, like Calcium Chloride to enhance dissolution can work. Areas with traffic can help break up the ice and salt and force the salt to dissolve better. For a typical driveway or walkway though, the best bet is to move on to another salt.
Calcium Chloride, the pellet salt, has one major advantage. It melts snow and ice effectively down below 0 degrees F. The basic science behind this is simple. The more extra particles you add to water, the lower the temperature it will melt at. Calcium Chloride pellets give off more of these particles. It draws moisture from the air or surroundings and is able to dissolve into snow and ice at lower air temperatures than rock salt. When it begins to dissolve it gives off heat, helping to melt snow and ice at a quicker rate.
The negatives when working with Calcium Chloride is that it costs about 5 to 6 times more than rock salt and it has to be stored properly to maintain its ability to absorb moisture. If left unsealed or in moist air, it will cake and can turn into a slushy salt mix that isn’t very effective to use and is nearly impossible to spread. It’s best to buy calcium chloride in resealable containers and avoid damaging the container.
The biggest drawback of sodium chloride(rock salt) is that it can cause significant damage to roads, plants, and waterways. Calcium chloride still can have these same negative effects but they are much more pronounced with rock salt. Rusting on cars and grass die back along edges are typical signs of over exposure to rock salt.
If you’re wondering about why we don’t try to use Calcium chloride or another salt besides rock salt the answers are pretty simple. First is money. Nothing compares in price and effectiveness to rock salt. Second is storage. Calcium Chloride is difficult to store since it absorbs water and cakes up easily.
Other chemicals that are used to melt snow include Magnesium chloride, several organic compounds and fertilizers, and almost all of them have some of the same drawbacks. Magnesium chloride absorbs moisture like Calcium Chloride and is more expensive, most fertilizers and organic compounds are corrosive when used as a snow and ice melting compound and are difficult to store because they are liquid or absorb moisture.
If you still have questions please feel free to leave a comment or contact us with the form below.