Salt & ice: snow removal questions

Question 1

At what temperature does rock salt stop working?

Accepted Answer

Rock salt works best above about 15°F, measured at the pavement, not in the air. Below that it slows down sharply, and liquid magnesium or calcium chloride, which work down to about -10°F and -20°F, take over. Pavement and air temperature are often ten degrees apart. A sunny lot can be above freezing at dusk with the air at 30, and a shaded loading dock can be below 15 when the forecast says 25. Salt brine works in the same range as rock salt. It is faster and easier to place, not colder.

Question 2

Why is my parking lot icy even though it was salted?

Accepted Answer

Usually because the pavement got too cold for rock salt, or because meltwater refroze after the treatment. Snow piles melting across the lot in the afternoon and freezing overnight at the low spots are the most common cause. Shaded corners, north-facing docks and the strip under a building overhang ice first. They need their own attention in the plan. A single application does not last through a long storm or a thaw and refreeze cycle. That is why salting is a separate job from plowing and runs on its own weather.

Question 3

Why did my contractor salt when it didn't snow?

Accepted Answer

Because ice forms without snow. Freezing rain, drizzle on a cold surface, and meltwater refreezing after a thaw all make a lot slippery with no plowable snow at all. Salt put down before or at the start of an ice event, called anti-icing, stops ice from bonding to the pavement and takes less material than melting it afterward. Your service report should say what was applied and why. If you pay per application, it is fair to ask what weather triggered each one.

Question 4

What is pre-treatment or brine, and is it worth it?

Accepted Answer

Pre-treatment is putting salt brine or treated salt on the pavement before a storm so snow and ice do not bond to it. It makes plowing cleaner and usually takes less material than melting ice after it forms. Brine is salt dissolved in water, most effective at about 23.3% concentration. It works in the same temperature range as rock salt, so it is not a cold-weather fix. It is worth it most before ice events and at the start of storms that begin as rain or near freezing. It is less useful when the pavement is already very cold.

Question 5

Is sand better than salt for ice?

Accepted Answer

Sand does not melt anything; it only adds traction on top of ice. It is the right tool when it is too cold for de-icers to work, and the wrong one at 30°F, where it becomes grit to sweep up in spring. Sand and other abrasives are also tracked indoors and wash into storm drains, so they are best used where traction is needed right now and melting is not possible.

Question 6

Does salt damage concrete sidewalks?

Accepted Answer

De-icers can speed up surface scaling on concrete, mostly by adding freeze-thaw cycles, and the risk is highest on concrete less than a year old. The concrete industry's guidance is not to use de-icing salts in the first year after concrete is placed, and never to use ammonium nitrate or ammonium sulfate on concrete at all. Well-built, air-entrained concrete that has cured properly handles normal de-icer use much better than new or poorly finished slabs. If you poured new walks this year, tell your contractor before the season. Clean sand for traction is the usual answer on those surfaces for the first winter. Sealing concrete and using only as much material as the conditions need both reduce the damage.

Question 7

What is the difference between rock salt, calcium chloride and magnesium chloride?

Accepted Answer

Rock salt is the cheapest and melts the most ice, but works best on pavement above about 15°F. Calcium chloride and magnesium chloride keep working much colder, to about -20°F and -10°F in Minnesota's Smart Salting guidance, and cost more. Calcium and magnesium chloride can leave a slick surface if over-applied, so they are used where and when they are needed rather than across a whole lot. Blends and treated salt sit in between. Pavement temperature, not the air temperature in the forecast, decides which one is right on a given morning.

Question 8

What ice melt is safe for pavers and natural stone?

Accepted Answer

Use the least material that works and keep it off stone where you can. Excess de-icer degrades concrete, asphalt and natural stone, according to Minnesota's Smart Salting guidance, and sand can clog permeable pavers. Pavers and stone steps belong on the site plan so they are treated at walkway rates with a walkway material, not at the rate a truck spreader puts down on a lot. Ask the paver or stone manufacturer which de-icers their warranty allows. Some name specific products or exclusions.

Question 9

Is ice melt safe for pets and landscaping?

Accepted Answer

No chloride ice melt is harmless to plants and animals. All of them can burn turf and shrubs along walks and irritate pets' paws, and what washes off reaches streams, where chloride harms aquatic life. The practical fixes are spreaders with shields or drop spreaders along plantings, lower calibrated rates, and sweeping up leftover material after the storm. Products marketed as pet-safe or plant-safe vary. The amount put down usually matters more than the label.

Salt & ice

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