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In this video, Mason Mark McCullough walks Kevin O’Connor through how to choose the best ice melt for your driveway and walkways. There are basically two materials to make surfaces less slippery in the winter: salt and sand.
Salt
Salt has a lower freezing point than water, so when you put salt on ice, it lowers the ice’s freezing point to about zero degrees Fahrenheit, which forces the ice to revert back to water. Rock salt is the cheapest of the ice melters and works fast.
Calcium chloride is another melt that Mark likes, it can melt at lower temperatures but it is more expensive. Mark points out that these salts aren’t exactly nature friendly, they can damage plants and nearby waterways when it runs off the concrete as it melts. Rock salt and calcium chloride burn pets’ paws and can be toxic if ingested.
For a pet safe and environmentally friendly salt option, use magnesium chloride. Unfortunately, it is the most expensive of the ice melters.
Pro Tip: Consider pretreating your driveway before a storm instead of deicing after the fact. As This Old House Magazine advises, acetate or formate-based anti-icers—applied with a pump sprayer before the flakes start to fly—can prevent ice from bonding to surfaces in the first place. “When snow does fall, the bottom ½-inch layer will turn into slush that’s easy to shovel, sweep, or blow away.” These alternatives also avoid the corrosion, concrete spalling, and pet hazards associated with chloride-based products.
Calcium chloride is available in both pellet and flake form. As Mark explains on Ask This Old House, “The difference being is the flake just reacts with the surface where the pellet really takes in burrows” all the way down through the ice. So when choosing calcium chloride, pellets are the better option for thick, packed ice.
Sand
Sand provides no melting, just friction. Sand is abrasive, so when it’s placed on top of the ice, it increases traction and makes it safer to walk on a slippery surface immediately. Sand is only effective when it’s on the surface of the ice, so if another snowstorm comes, you will need to reapply the sand.
Pro Tip: Mark McCullough, landscaping expert on Ask This Old House, explains that sand works by embedding itself into the ice surface: “You’re not gonna get any melting out of that, but you are gonna get some friction. It just grinds into the ice a little bit, so if your foot goes into that area, you’re not gonna have too much slippage.”
Sand/Salt Combination
Mark shows Kevin his third category of de-icers, a sand/salt combination. Mixes are usually a good go-to because you can minimize the amount of salt in the mix, which reduces damage to walkways and the environment, while still providing some ice melting ability and traction from the sand.
While you can use salt on asphalt, it is bad for concrete. Salt can corrode the integrity of the concrete over time by exacerbating the freeze-thaw cycle, which is how potholes and cracks form.
When it comes to stone surfaces, the salt component in a sand/salt mix still matters. As Mark notes, salt works fine on asphalt and granite, which is a very tough product, but he cautions against using it on bluestone or limestone. And even granite steps can be vulnerable: “If a granite step had a masonry joint, you do have to put it down in cement or mortar. And once that happens, you’re now a masonry unit. So if you add salt, it’s gonna damage it.” Keep the mix away from any mortared joints.
Resources
Mark discussed a few different types of driveway and walkway de-icers. Both the rock salt and the sand were generic products that can be found at any home center.
The rock salt/sand combination was a Road Runner 20lb Ice Melt Blend Bag, which is manufactured by Scotwood Industries.
