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How Salt Melts Ice

By by Molly Cochran, Staff Writer
November 04, 2013, 8:51:21 AM EST

Granulate salt is one method used to melt ice on icy roads. Distributing salt onto icy roads lowers the freezing temperature. The more salt you add to the ice, the more it lowers the freezing temperature. For example, the lowest temperature that salt can melt ice is 15 degrees, according to AccuWeather Senior Meteorologist Mike Pigott.

If you have an icy road with a temperature of 15 degrees, you would need more salt than if it was 32 degrees outside, just to melt the ice.

"Salt interferes with water forming bonds in order to form solids," Pigott said.


Transportation companies rely on an accurate weather forecast in order to prep for winter storms. Eugene Balum, assistant press secretary, and Nick Martino, assistant district executive of maintenance, for Philadelphia region of the Pennsylvania Department of Transportation agreed that an accurate weather forecast is extremely important for knowing when to salt roads.

“A bad forecast could cost money,” said Balum.

The day or night before the predicted storm, the Philadelphia region district drivers will spray a salt brine solution to the main interstates and heavily traveled roads, according to Balum.

“The salt brine will cause the water to evaporate and prevent the snow from bounding to the pavement,” he said.

The Philadelphia-area PennDOT brings their drivers in two hours prior to any predicted storm. According to Martino, if the forecast calls for 4-6 inches of snow, they always plan for the higher amount, 6 inches, to prepare for salting.

Temperature also plays a role in the type of salt solution that is used on roads.

The Philadelphia region district still salts roads in the mid- to high teens.

“Once it hits 15 degrees, that is when you have to be careful, because of wind chill and higher elevation,” Martino said.

If the temperature dips below 15 degrees, District 6-0 adds calcium floride to the granulate salt because the calcium floride with the salt will melt the ice until about 10 degrees, according to Martino.

Another alternative that the Philadelphia district uses is known as anti-skid. Anti-skid is a stone and sand mixture that mixes in with the granulate salt. Although this mixture won't melt ice, it will help provide traction for vehicles.

There are a lot of different elements and preparations that contribute to make the roads drivable in the winter months, but an accurate weather forecast could make all the difference and, like Balum said, save money.

For your safety, during the winter months don't forget to watch the weather and keep eyes peeled for changing weather conditions.

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