What Is Road Salt? And Other FAQs

At what temperature does road salt stop working? What are its benefits? Are there any drawbacks? If you’ve lived anywhere with freezing winters, you’re likely familiar with road salt. This makes it easier to drive along streets and highways when the temperature drops and slippery roads become a danger. Let’s find out more about road salt and the different nuances to this life-saving but controversial substance.

What Is Road Salt?

More often than not, road salt is made of sodium chloride (NaCl), which is the same chemical composition used for table salt. Road salt is often known as rock salt due to its larger granules. Another difference is that while table salt goes through a purification process, road salt tends to retain impurities like lead, aluminum, phosphorus, and iron. This leaves it with a brown or gray color as opposed to white table salt.

Certain highway departments will use calcium chloride (CaCl2) which, while cheaper, is less effective. You need about three times the amount of calcium chloride compared to sodium chloride when salting roads.

Some road salts include additives such as sodium hexacyanoferrate or sugar to keep them from caking during delivery.

How Does Road Salt Work?

Road salt works by lowering the freezing point of water. This makes it more difficult for water to freeze on the road, which in turn minimizes icy surfaces for drivers. Road salt is commonly applied to roads and sidewalks with a brine mixture of the road salt and some water. This is to provide the small amount of water needed upon application for road salt to do its thing.

At What Temperature Does Road Salt Stop Working?

The effective temperature of road salt is over 15 or 20 degrees Fahrenheit. As the temperature decreases, road salt becomes less effective. This means the amount of ice that can be melted per pound of salt goes down. The colder it gets, the more salt you need to melt the same amount of ice. Road salt also melts ice at slower speeds when it’s colder, which isn’t ideal for highway deicing.

What Are the Benefits of Using Road Salt?

Using road salt as a deicer helps prevent car accidents during the colder months. According to the American Highway Users Alliance, applying road salt reduces accidents by up to 93%. In addition, if road salt is applied before a winter storm, it can reduce the resulting ice on the road, making deicing the road much easier.

Using road salt that’s been mixed with chemicals and ash or sand also results in more traction on winter roads and ice-packed streets. The chemicals help the salt melt the ice, while the ash or sand make for a more textured surface to walk or drive on.

How Does Road Salt Affect the Road and the Environment?

Unfortunately, while road salt helps reduce accidents and keep roads drivable, it does have its drawbacks. After all, come spring and summer, all that salt doesn’t simply evaporate. It splits into sodium and chloride ions and gets washed away into the roadside. This can devastate the local ecosystem. The plants that absorb all that salt can either die or negatively affect the insects and animals that feed on them.

There’s also the effects road salt has on your car. Because of its corrosive nature, salt can eat away at your car’s paint and brake and fuel lines. That’s why it’s important to clean your car’s undercarriage and exterior after driving on salted roads.

Because of these drawbacks, many companies have begun to explore alternatives such as porous pavement and solar-powered roadways.

Now you know what road salt is made of, how it works, its effective temperature, and its advantages and disadvantages. While it can be a useful winter tool, it’s very important to start considering road salt’s environmental impact and possible alternatives or solutions.