Kentucky and South Carolina Salt Roads With Calcium Fluoride? No Calcium Chloride

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S.C. Department of Transportation officials … they started pre-treating the major bridges about midnight Monday with 4,000 gallons of salt brine and calcium fluoride mix to keep the ice from sticking. They followed that with more than 125 tons of salt, according to Robert Clark, engineering administrator for the district that covers the Lowcountry.

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Kentucky Transportation workers pre-treated many roads to help keep snow from sticking. …

“But we are prepared, we’ve got close to 20,000 tons of salt, 95,000 gallons of calcium fluoride, of course we can make brine at each county barn on site,” says Keirsten Jaggers from the Kentucky Transportation Cabinet.

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From Richard Windsor

Dear James,

There is no way physically that calcium fluoride is useful as a de-icing agent. I’d guess, from my previous contact with the press, that it’s a reporters error, calling chloride, fluoride. You are closer to the action than me, ring up the reporter (or send her an email and ask her if she made a mistake.

The reason calcium chloride is used as a de-icer is that it is highly soluble and it has an exothermic reaction on dissolving. it gives off heat. So the increased osmolarity of the solution causes freezing point depression (the solution freezes at less than zero Celsius) and the exothermic reaction of the calcium chloride dissolving initiates a positive feedback loop, the more water formed, the more of the material dissolves and the more heat given off. A near perfect de-icer.

Calcium fluoride, on the other hand, is barely soluble, it has no exothermic reaction and has no more use than grit spread on an icy road to improve traction.

Richard Windsor

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