Road salt

Road salt (also known as deicing salt, rock salt, snow salt or grit salt) is a salt used mainly as an anti-slip and deicing agent for roads, sidewalks and other transportation surfaces during the winter. The most commonly used form is sodium chloride (NaCl), though other salts such as calcium chloride and magnesium chloride are also employed, especially in colder temperatures. When used in its solid form, road salt is often pre-wet to accelerate the ice-melting process. Road salt lowers the freezing point of water through freezing-point depression and thus prevents ice formation, which in turn improves traction and safety for vehicles and pedestrians.

The widespread use of road salts began in the 20th century and is since standard practice in many regions with yearly snowfall, especially in Europe and North America. Millions of tons of salt are applied to road surfaces yearly, making it one of the most extensively used chemical agents in urban infrastructure. It has become popular due to its effectiveness, low cost, and ease of application.

Road salts have adverse effects on the environment. Chloride ions from road salt can accumulate in soils, surface waters, and groundwater, where they persist and may harm aquatic ecosystems, roadside vegetation, and drinking water supplies. Road salt also accelerates corrosion of vehicles, bridges, and reinforced concrete, leading to increased maintenance costs. These concerns have prompted research into alternative de-icing materials, improved application techniques, and policies aimed at reducing salt use while maintaining road safety.