What does salt do to icy roads?


If you live in the UK in the winter, then you have probably seen newspapers offer headlines about how awful the winter is and there is never enough salt or grit to go around. British people love talking about the weather and the pres always love a crisis, so the combination means it makes a perfect headline for a winter’s day.

In short; Gritting roads makes them safer for drivers than not Gritting roads.

There are always plenty of lawyers around to find someone to blame. In most of the slip and trip cases there is a cast iron defence, so long as the landowner shows Due Diligence; in anticipating and identifying the risk and undertaking a suitable course of action to reduce that risk.

Local authorities spread salt on the main roads to melt the ice, thus reducing the risk of driving on icy roads.

Estates roads, driveways, car parks, entrances and delivery compounds are not gritted by most Local Authorities. They are gritted by contractors, like Kentcare, who will supply the grit they spread. This is usually a sufficient course of action for showing Due Diligence backed up by our records.

Otherwise willing members of the community will spread the grit as they deem it necessary from outdoor containers, grit bins, which are usually regularly topped up by contactors like Kentcare! This puts a greater burden of responsibility on tenants and/or other users of your grit bins.

So why does salt work?

Salt lowers the freezing/melting point of water, so idea is to take advantage of the lower melting point.

Ice forms when the­ temperature of water reaches 32 degrees Fahrenheit (0 degrees Celsius). When you add salt, that temperature drops: A 10-percent salt solution freezes at 20 F (-6 C), and a 20-percent solution freezes at 2 F (-16 C). On a roadway, this means that if you sprinkle salt on the ice, you can melt it. The salt dissolves into the liquid water in the ice and lowers its freezing point.

If you ever watch salt melting an ice cube, you can see the dissolving process happen — the ice immediately around the grain of salt melts, and the melting spreads out from that point. If the temperature of the roadway is lower than 15 F or so, then the salt on its own really won’t have much significant effect — the solid salt cannot get into the structure of the solid water to start the dissolving process. The impurities in the salt that you see in grit bins (an orangey brown colour) is often enough to help with traction but otherwise, spreading sand over the top of the ice to provide greater grip is a better option. This is why sand is sometimes used when salt is in short supply.

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If this little bit of school science is still too much, give us a call or email and we will put your mind at rest.