Most roads are treated with coarse rock salt made of sodium chloride (NaCl), often with additives to help it work better in the cold and spread more evenly.

Main types of “road salt”

  • Rock salt (sodium chloride/NaCl): The standard road salt, mined from underground deposits and crushed into coarse grains; it is cheap and works best just below freezing down to about 5–15°F (around −10 to −15°C).
  • Treated rock salt: Regular sodium chloride that has been pre-wetted or coated with liquids like magnesium chloride or other agents so it sticks to the road better, scatters less, and works at slightly lower temperatures.
  • Brine (saltwater solution): Salt dissolved in water and sprayed on roads before storms to prevent ice bonding to the pavement; usually based on sodium chloride but sometimes blended with other chlorides.

Other de‑icing salts used

In colder conditions or sensitive areas, road agencies may blend or replace rock salt with other salts:

  • Calcium chloride (CaCl₂): Works at much lower temperatures (down to around −25°F or −32°C), acts quickly, and is often used in liquid form or mixed with rock salt.
  • Magnesium chloride (MgCl₂): Effective in colder weather than plain rock salt and somewhat less corrosive, sometimes used to coat rock salt granules.
  • Potassium chloride (KCl): Less common on roads; may be used in blends, is gentler on vegetation but not as effective in very low temperatures.

Quick forum-style takeaway

When people say “they salted the roads,” they almost always mean coarse rock salt (sodium chloride) spread from trucks, sometimes pretreated with liquids like magnesium or calcium chloride to boost performance in the cold and reduce waste.

TL;DR: The main salt used on roads is coarse rock salt made of sodium chloride, often enhanced with liquid de‑icers like magnesium or calcium chloride for better low‑temperature performance.

Information gathered from public forums or data available on the internet and portrayed here.