De-icing is defined as the removal of existing snow, ice or frost from a roadway, airport runway, or another surface. It includes both mechanical means, such as plowing or scraping, and chemical means, such as application of salt or other ice-melting chemicals. Anti-icing is treatment with ice-melting chemicals before or during the onset of a storm to prevent or delay the formation and adhesion of ice and snow to the surface. Brine, or wetted salt, is usually applied shortly before the beginning of a snowstorm. When properly performed, anti-icing can significantly reduce the amount of salt required and allow easier removal by mechanical methods, including plowing.
The de-icing of roads has historically been accomplished by snowplows or specially-designed dump trucks that spread salt, often mixed with sand and gravel, onto slick roads. Rock salt is normally used because it is inexpensive and readily available in large quantities. However, brine freezes at −18 °C (0 °F), and so it is ineffective at these low temperatures. It also has a strong tendency to cause corrosion, rusting the steel used in most vehicles and the rebar in concrete bridges. More recent snow melters use other salts, such as calcium chloride and magnesium chloride, which not only decrease the freezing point of water to a much lower temperature but also produce an exothermic reaction, whose dissipated heat further aids in melting. Besides, they are somewhat safer for concrete sidewalks, but excess should still be removed
The rock salt used on roads is the same salt that is used on your dinner table. The larger salt pieces are typically ground down to finer crystals before being placed on your supermarket shelves. Salt is collected by underground salt mines and then processed, packaged and distributed. The largest salt mining company in the United States, American Rock Salt, produces 10,000 to 18,000 tons of salt each day.
Salting roads works by altering the freezing point of water. Water with a higher salt content has a lower freezing point than water with less salinity. This accounts for the difference in Celsius and Fahrenheit temperature scales; 0 degrees C is the freezing point of freshwater, while 0 degrees F is the freezing point of brine solution that Daniel Fahrenheit mixed. Salting icy roads and walkways lowers the freezing point of the water that forms ice which leads to melting and prevents falling snow or rain from being able to freeze.
Whereas rock salt melts ice, sand does not. Sand, because it is an abrasive material, is applied to icy roads to provide traction. It can capably create traction on the ice at any temperature, whereas rock salt is not effective in extreme cold. But sand is only effective if it is on the surface of the ice. If it gets buried under snow, it needs to be reapplied.
Excessive amounts of sand can collect into drains and drainage areas, so clean-up of sand after storms is important or you can have problems come spring. For homeowners who want to go with sand to help manage ice on their walks and drives, use sandbox sand as opposed to mason’s sand, which is too fine.
Other abrasive materials like kitty litter, sawdust, or wood ashes can be used to create traction on icy walkways if sand is not available.
Of course, the best solution to preventing ice buildup is to keep the snow off your drive or walkway so that it won’t compact and freeze. Shovel or snow blow early and often. See you on the other side of winter!