Is Rock Salt Bad for My Driveway?

21-Feb-2019 | by Scott Bennett

It may be February, but it is still winter here in Salt Lake City, Utah. Every few days, we get another winter storm warning and more inches of snow in our driveways. Many of us are shoveling our driveways often, even a few times a week. We know that snow plows dump a lot of rock salt on our roadways. It appears to work. It seems like a snowplow will go by and minutes later, the latest layer of snow is starting to melt, making it less dangerous to drive around town.

Even though it’s commonly used on Utah roadways, is rock salt bad for our driveways? Is it bad for concrete? Is it bad for asphalt? The answer to all of these questions is yes, yes, yes! Rock salt is bad for our driveways. It is commonly used on roadways because of how cheap it is. And it does melt snow and ice down to 20 degrees F. The problem is that it only melts snow and ice to 20 degrees F.

Most of our driveways are made of concrete which is very porous. Water gets absorbed and trapped inside. It freezes and the water expands, causing pieces of concrete to chip off. Rock salt makes worse the freezing—thawing cycle. Rock salt will melt snow and ice to 20 degrees F. When it gets colder than that, water will refreeze.

Other ice melts are safer for your driveway and more effective melting ice. For example, calcium chloride is less damaging than rock salt because it will melt to -13 degrees F. That’s a 33 degree difference from rock salt. Rock Salt is also bad for our driveways because it is bad for plants. What happens when you put rock salt on your driveway and then it snows? The snow starts to melt as you begin to shovel. Most of us have a pattern to our shoveling. In fact, we have shoveling down to an art form! We pile it in all the same places, usually to the side of our driveway and walkways.

Rock salt is suffocating to plants. A little bit won’t hurt, but as we shovel again and again, the rock salt in our snow will start to build up the more times we pile it on our lawn or our flowerbeds. In the springtime, some homeowners are sad to see dead or almost dead plants, trying to recover from too much rock salt.

If you worry that your plants are getting too much rock salt buildup, try to pile snow in different places each time it snows as much as you can. Then, when spring comes, get your garden hose and thoroughly water questionable areas. Hopefully, you will be able to dilute the impact of the rock salt on your plants.

Calcium chloride and magnesium chloride are both recommended for use on driveways. They aren’t as tough on driveways or plants. Hopefully, we will only have a few more weeks of snow and shoveling and worrying about ice melt will be in our past, at least until the end of the year.